Publications by authors named "Kipruto Kirwa"

22 Publications

  • Page 1 of 1

Preterm birth and PM in Puerto Rico: evidence from the PROTECT birth cohort.

Environ Health 2021 Jun 11;20(1):69. Epub 2021 Jun 11.

Department of Civil and Environmental Engineering, Tufts University, Anderson Hall, 200 College Avenue, Medford, MA, 02155, USA.

Background: Preterm birth (PTB, birth before 37 weeks of gestation) has been associated with adverse health outcomes across the lifespan. Evidence on the association between PTB and prenatal exposure to air pollutants is inconsistent, and is especially lacking for ethnic/racial minority populations.

Methods: We obtained data on maternal characteristics and behaviors and PTB and other birth outcomes for women participating in the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) cohort, who lived in municipalities located along the North Coast of Puerto Rico. We assessed pre-natal PM exposures for each infant based on the nearest US Environmental Protection Agency monitor. We estimated prenatal phthalate exposures as the geometric mean of urinary measurements obtained during pregnancy. We then examined the association between PM and PTB using modified Poisson regression and assessed modification of the association by phthalate exposure levels and sociodemographic factors such as maternal age and infant gender.

Results: Among 1092 singleton births, 9.1% of infants were born preterm and 92.9% of mothers had at least a high school education. Mothers had a mean (standard deviation) age of 26.9 (5.5) years and a median (range) of 2.0 (1.0-8.0) pregnancies. Nearly all women were Hispanic white, black, or mixed race. Median (range) prenatal PM concentrations were 6.0 (3.1-19.8) μ g/m. Median (interquartile range) prenatal phthalate levels were 14.9 (8.9-26.0) and 14.5 (8.4-26.0), respectively, for di-n-butyl phthalate (DBP) and di-isobutyl phthalate (DiBP). An interquartile range increase in PM was associated with a 1.2% (95% CI 0.4, 2.1%) higher risk of PTB. There was little difference in PTB risk in strata of infant sex, mother's age, family income, history of adverse birth outcome, parity, and pre-pregnancy body mass index. Pregnancy urinary phthalate metabolite levels did not modify the PM-PTB association.

Conclusion: Among ethnic minority women in Puerto Rico, prenatal PM exposure is associated with a small but significant increase in risk of PTB.
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June 2021

Fine-Scale Air Pollution Models for Epidemiologic Research: Insights From Approaches Developed in the Multi-ethnic Study of Atherosclerosis and Air Pollution (MESA Air).

Curr Environ Health Rep 2021 06;8(2):113-126

Departments of Environmental and Occupational Health Sciences, Epidemiology, and Medicine, University of Washington, Seattle, WA, USA.

Purpose Of Review: Epidemiological studies of short- and long-term health impacts of ambient air pollutants require accurate exposure estimates. We describe the evolution in exposure assessment and assignment in air pollution epidemiology, with a focus on spatiotemporal techniques first developed to meet the needs of the Multi-ethnic Study of Atherosclerosis and Air Pollution (MESA Air). Initially designed to capture the substantial variation in pollutant levels and potential health impacts that can occur over small spatial and temporal scales in metropolitan areas, these methods have now matured to permit fine-scale exposure characterization across the contiguous USA and can be used for understanding long- and short-term health effects of exposure across the lifespan. For context, we highlight how the MESA Air models compare to other available exposure models.

Recent Findings: Newer model-based exposure assessment techniques provide predictions of pollutant concentrations with fine spatial and temporal resolution. These validated models can predict concentrations of several pollutants, including particulate matter less than 2.5 μm in diameter (PM), oxides of nitrogen, and ozone, at specific locations (such as at residential addresses) over short time intervals (such as 2 weeks) across the contiguous USA between 1980 and the present. Advances in statistical methods, incorporation of supplemental pollutant monitoring campaigns, improved geographic information systems, and integration of more complete satellite and chemical transport model outputs have contributed to the increasing validity and refined spatiotemporal spans of available models. Modern models for predicting levels of outdoor concentrations of air pollutants can explain a substantial amount of the spatiotemporal variation in observations and are being used to provide critical insights into effects of air pollutants on the prevalence, incidence, progression, and prognosis of diseases across the lifespan. Additional enhancements in model inputs and model design, such as incorporation of better traffic data, novel monitoring platforms, and deployment of machine learning techniques, will allow even further improvements in the performance of pollutant prediction models.
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June 2021

Non-nutritive suck and airborne metal exposures among Puerto Rican infants.

Sci Total Environ 2021 Oct 26;789:148008. Epub 2021 May 26.

Department of Civil and Environmental Engineering, Tufts University, 200 College Ave, Medford, MA 02155, USA. Electronic address:

Air pollution has been shown to impact multiple measures of neurodevelopment in young children. Its effects on particularly vulnerable populations, such as ethnic minorities, however, is less studied. To address this gap in the literature, we assess the associations between infant non-nutritive suck (NNS), an early indicator of central nervous system integrity, and air pollution exposures in Puerto Rico. Among infants aged 0-3 months enrolled in the Center for Research on Early Childhood Exposure and Development (CRECE) cohort from 2017 to 2019, we examined associations between exposure to fine particulate matter (PM) and its components on infant NNS in Puerto Rico. NNS was assessed using a pacifier attached to a pressure transducer, allowing for real-time visualization of NNS amplitude, frequency, duration, cycles/burst, cycles/min and bursts/min. These data were linked to 9-month average prenatal concentrations of PM and components, measured at three community monitoring sites. We used linear regression to examine the PM-NNS association in single pollutant models, controlling for infant sex, maternal age, gestational age, and season of birth in base and additionally for household smoke exposure, age at testing, and NNS duration in full models. Among 198 infants, the average NNS amplitude and burst duration was 17.1 cmHO and 6.1 s, respectively. Decreased NNS amplitude was consistently and significantly associated with 9-month average exposure to sulfur (-1.026 ± 0.507), zinc (-1.091 ± 0.503), copper (-1.096 ± 0.535) vanadium (-1.157 ± 0.537), and nickel (-1.530 ± 0.501). Decrements in NNS frequency were associated with sulfur exposure (0.036 ± 0.018), but not other examined PM components. Our findings provide new evidence that prenatal maternal exposure to specific PM components are associated with impaired neurodevelopment in Puerto Rican infants soon after birth.
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October 2021

Residential proximity to major roads and fecundability in a preconception cohort.

Environ Epidemiol 2020 Dec 11;4(6):e112. Epub 2020 Nov 11.

Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts.

Emerging evidence from animal and human studies indicates that exposure to traffic-related air pollution may adversely affect fertility.

Methods: Among 7,342 female pregnancy planners from the United States and 1,448 from Canada, we examined the association between residential proximity to major roads and fecundability, the per-cycle probability of conception. From 2013 to 2019, women 21-45 years old who were trying to conceive without fertility treatment completed an online baseline questionnaire and follow-up questionnaires every 8 weeks for up to 12 months or until pregnancy. We geocoded residential addresses reported at baseline and during follow-up, and calculated distance to nearest major roads and length of major roads within buffers of 50, 100, 300, and 400 meters around the residence as proxies for traffic-related air pollution. We used proportional probabilities regression models to estimate fecundability ratios (FRs) and 95% confidence intervals (CIs), adjusting for individual- and neighborhood-level characteristics.

Results: In the United States, the FR comparing women who lived <50 meters with those who lived ≥400 meters from the closest major road was 0.88 (95% CI = 0.80, 0.98). The association among Canadian women was similar in magnitude, but less precise (FR = 0.93; 95% CI = 0.74, 1.16). Likewise, length of major roads within buffers of 50 and 100 meters was associated with lower fecundability in both countries; associations were attenuated within larger buffers.

Conclusions: These results are consistent with the hypothesis that traffic-related air pollution or other near-road exposures may adversely affect fecundability.
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December 2020

Maternal exposure to PM during pregnancy and asthma risk in early childhood: consideration of phases of fetal lung development.

Environ Epidemiol 2021 Apr;5(2)

Department of Epidemiology, University of Washington, Box 357236, Seattle WA, USA 98195-7236.

Background: Increasingly studies suggest prenatal exposure to air pollution may increase risk of childhood asthma. Few studies have investigated exposure during specific fetal pulmonary developmental windows.

Objective: To assess associations between prenatal fine particulate matter exposure and asthma at age 4.

Methods: This study included mother-child dyads from two pregnancy cohorts-CANDLE and TIDES-within the ECHO-PATHWAYS consortium (births in 2007-2013). Three child asthma outcomes were parent-reported: ever asthma, current asthma, and current wheeze. Fine particulate matter (PM) exposures during the pseudoglandular (5-16 weeks gestation), canalicular (16-24 weeks gestation), saccular (24-36 weeks gestation), and alveolar (36+ weeks gestation) phases of fetal lung development were estimated using a national spatiotemporal model. We estimated associations with Poisson regression with robust standard errors, and adjusted for child, maternal, and neighborhood factors.

Results: Children (n=1469) were on average 4.3 (standard deviation 0.5) years old, 49% were male, and 11.7% had ever asthma; 46% of women identified as black and 53% had at least a college/technical school degree. A 2 μg/m higher PM exposure during the saccular phase was associated with 1.29 times higher risk of ever asthma (95% CI: 1.06-1.58). A similar association was observed with current asthma (RR 1.27, 95% CI: 1.04-1.54), but not current wheeze (RR 1.11, 95% CI: 0.92-1.33). Effect estimates for associations during other developmental windows had confidence intervals that included the null.

Conclusions: Later phases of prenatal lung development may be particularly sensitive to the developmental toxicity of PM.
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April 2021

Ambient air pollution and risk of respiratory infection among adults: evidence from the multiethnic study of atherosclerosis (MESA).

BMJ Open Respir Res 2021 03;8(1)

Departments of Environmental and Occupational Health Sciences, Medicine, and Epidemiology, University of Washington, Seattle, Washington, USA.

Background: Air pollution may affect the risk of respiratory infection, though research has focused on uncommon infections or infections in children. Whether ambient air pollutants increase the risk of common acute respiratory infections among adults is uncertain, yet this may help understand whether pollutants influence spread of pandemic respiratory infections like COVID-19.

Objective: To estimate the association between ambient air pollutant exposures and respiratory infections in adults.

Methods: During five study examinations over 12 years, 6536 participants in the multiethnic study of atherosclerosis (MESA) reported upper respiratory tract infections, bronchitis, pneumonia or febrile illness in the preceding 2 weeks. Using a validated spatiotemporal model, we estimated residential concentrations of ambient PM, NO and NO for the 2-6 weeks (short-term) and year (long-term) prior to each examination.

Results: In this population aged 44-84 years at baseline, 10%-32% of participants reported a recent respiratory infection, depending on month of examination and study region. PM, NO and NO concentrations over the prior 2-6 weeks were associated with increased reporting of recent respiratory infection, with risk ratios (95% CIs) of 1.04 (1.00 to 1.09), 1.15 (1.10 to 1.20) and 1.21 (1.10 to 1.33), respectively, per increase from 25th to 75th percentile in residential pollutant concentration.

Conclusion: Higher short-term exposure to PM and traffic-related pollutants are associated with increased risk of symptomatic acute respiratory infections among adults. These findings may provide an insight into the epidemiology of COVID-19.
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March 2021

Patient Transfers and Their Impact on Gaps in Clinical Care: Differences by Gender in a Large Cohort of Adults Living with HIV on Antiretroviral Therapy in South Africa.

AIDS Behav 2021 Feb 20. Epub 2021 Feb 20.

Department of Epidemiology, Brown University, Box G-S121-2 121 South Main Street, Providence, Rhode Island, RI, 02903, USA.

For people living with HIV (PLWH), patient transfers may affect engagement in care. We followed a cohort of PLWH in Cape Town, South Africa who tested positive for HIV in 2012-2013 from ART initiation in 2012-2016 through December 2016. Patient transfers were defined as moving from one healthcare facility to another on a different day, considering all healthcare visits and recorded HIV-visits only. We estimated incidence rates (IR) for transfers by time since ART initiation, overall and by gender, and associations between transfers and gaps of > 180 days in clinical care. Overall, 4,176 PLWH were followed for a median of 32 months, and 8% (HIV visits)-17% (all healthcare visits) of visits were patient transfers. Including all healthcare visits, transfers were highest through 3 months on ART (IR 20.2 transfers per 100 visits, 95% CI 19.2-21.2), but increased through 36 months on ART when only HIV visits were included (IR 9.7, 95% CI 8.8-10.8). Overall, women were more likely to transfer than men, and transfers were associated with gaps in care (IR ratio [IRR] 3.06 95% CI 2.83-3.32; HIV visits only). In this cohort, patient transfers were frequent, more common among women, and associated with gaps in care.
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February 2021

Modeling residential indoor concentrations of PM , NO , NO , and secondhand smoke in the Subpopulations and Intermediate Outcome Measures in COPD (SPIROMICS) Air study.

Indoor Air 2021 May 28;31(3):702-716. Epub 2020 Dec 28.

Department of Environmental and Occupational Health Sciences, University of Washington, Seattle, WA, USA.

Increased outdoor concentrations of fine particulate matter (PM ) and oxides of nitrogen (NO , NO ) are associated with respiratory and cardiovascular morbidity in adults and children. However, people spend most of their time indoors and this is particularly true for individuals with chronic obstructive pulmonary disease (COPD). Both outdoor and indoor air pollution may accelerate lung function loss in individuals with COPD, but it is not feasible to measure indoor pollutant concentrations in all participants in large cohort studies. We aimed to understand indoor exposures in a cohort of adults (SPIROMICS Air, the SubPopulations and Intermediate Outcome Measures in COPD Study of Air pollution). We developed models for the entire cohort based on monitoring in a subset of homes, to predict mean 2-week-measured concentrations of PM , NO , NO , and nicotine, using home and behavioral questionnaire responses available in the full cohort. Models incorporating socioeconomic, meteorological, behavioral, and residential information together explained about 60% of the variation in indoor concentration of each pollutant. Cross-validated R for best indoor prediction models ranged from 0.43 (NO ) to 0.51 (NO ). Models based on questionnaire responses and estimated outdoor concentrations successfully explained most variation in indoor PM , NO , NO , and nicotine concentrations.
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May 2021

Estimating retention in HIV care accounting for clinic transfers using electronic medical records: evidence from a large antiretroviral treatment programme in the Western Cape, South Africa.

Trop Med Int Health 2020 08 8;25(8):936-943. Epub 2020 Jun 8.

Department of Epidemiology, Brown University, Providence, RI, USA.

Background: Estimates of retention in antiretroviral treatment (ART) programmes may be biased if patients who transfer to healthcare clinics are misclassified as lost to follow-up (LTFU) at their original clinic. In a large cohort, we estimated retention in care accounting for patient transfers using medical records.

Methods: Using linked electronic medical records, we followed adults living with HIV (PLWH) in Cape Town, South Africa from ART initiation (2012-2016) through database closure at 36 months or 30 June 2016, whichever came first. Retention was defined as alive and with a healthcare visit in the 180 days between database closure and administrative censoring on 31 December 2016. Participants who died or did not have a healthcare visit in > 180 days were censored at their last healthcare visit. We estimated the cumulative incidence of retention using Kaplan-Meier methods considering (i) only records from a participant's ART initiation clinic (not accounting for transfers) and (ii) all records (accounting for transfers), over time and by gender. We estimated risk differences and bootstrapped 95% confidence intervals to quantify misclassification in retention estimates due to patient transfers.

Results: We included 3406 PLWH initiating ART. Retention through 36 months on ART rose from 45.4% (95% CI 43.6%, 47.2%) to 54.3% (95% CI 52.4%, 56.1%) after accounting for patient transfers. Overall, 8.9% (95% CI 8.1%, 9.7%) of participants were misclassified as LTFU due to patient transfers.

Conclusions: Patient transfers can appreciably bias estimates of retention in HIV care. Electronic medical records can help quantify patient transfers and improve retention estimates.
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August 2020

Low birth weight and PM in Puerto Rico.

Environ Epidemiol 2019 Aug;3(4)

Department of Civil and Environmental Engineering, Tufts University, Medford, MA.

Background: Low birth weight (LBW) has been associated with adverse health outcomes across the lifespan. Among ethnic/racial minority populations, few studies have examined the association between LBW (<2,500 or ≥2,500 g) and prenatal exposure to air pollution, a key modifiable environmental risk factor.

Methods: We examined the association between LBW and prenatal exposure to PM in a Hispanic and black population in Puerto Rico between 1999 and 2013, adjusting for individual and municipality-level confounders. We used modified Poisson regression to estimate the association and performed sensitivity analyses treating birth weight as continuous or polychotomous. In secondary analyses, we applied a 2-stage mixed effects model suitable for longitudinally measured exposures and binary outcomes.

Results: Among 332,129 total and 275,814 term births, 12.2% and 6.3% of infants had LBW, respectively. Eighty-eight percent of mothers were Hispanic. Mean (SD) PM concentrations declined from 9.9 (1.7) μg/m in 1999 to 6.1 (1.1) μg/m in 2013. Mean birth weights dropped to 3,044 g in 2010 and rose steadily afterward. Among term births, a SD increase in PM was associated with a 3.2% (95% CI = -1.0%, 6.3%) higher risk of LBW. First (risk ratio, 1.02; 95% CI = 1.00, 1.04) and second (1.02; 95% CI = 1.01, 1.05) trimester exposures were associated with increased LBW risk. In a 2-stage approach that longitudinally modeled monthly prenatal exposure levels, a standard deviation increase in average PM was associated with higher risk of LBW (odds ratio, 1.04; 95% CI = 1.01, 1.08).

Conclusions: In Puerto Rico, LBW is associated with prenatal PM exposure.
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August 2019

Association of Long-term Ambient Ozone Exposure With Respiratory Morbidity in Smokers.

JAMA Intern Med 2020 Jan;180(1):106-115

Department of Medicine, Johns Hopkins University, Baltimore, Maryland.

Importance: Few studies have investigated the association of long-term ambient ozone exposures with respiratory morbidity among individuals with a heavy smoking history.

Objective: To investigate the association of historical ozone exposure with risk of chronic obstructive pulmonary disease (COPD), computed tomography (CT) scan measures of respiratory disease, patient-reported outcomes, disease severity, and exacerbations in smokers with or at risk for COPD.

Design, Setting, And Participants: This multicenter cross-sectional study, conducted from November 1, 2010, to July 31, 2018, obtained data from the Air Pollution Study, an ancillary study of SPIROMICS (Subpopulations and Intermediate Outcome Measures in COPD Study). Data analyzed were from participants enrolled at 7 (New York City, New York; Baltimore, Maryland; Los Angeles, California; Ann Arbor, Michigan; San Francisco, California; Salt Lake City, Utah; and Winston-Salem, North Carolina) of the 12 SPIROMICS clinical sites. Included participants had historical ozone exposure data (n = 1874), were either current or former smokers (≥20 pack-years), were with or without COPD, and were aged 40 to 80 years at baseline. Healthy persons with a smoking history of 1 or more pack-years were excluded from the present analysis.

Exposures: The 10-year mean historical ambient ozone concentration at participants' residences estimated by cohort-specific spatiotemporal modeling.

Main Outcomes And Measures: Spirometry-confirmed COPD, chronic bronchitis diagnosis, CT scan measures (emphysema, air trapping, and airway wall thickness), 6-minute walk test, modified Medical Research Council (mMRC) Dyspnea Scale, COPD Assessment Test (CAT), St. George's Respiratory Questionnaire (SGRQ), postbronchodilator forced expiratory volume in the first second of expiration (FEV1) % predicted, and self-report of exacerbations in the 12 months before SPIROMICS enrollment, adjusted for demographics, smoking, and job exposure.

Results: A total of 1874 SPIROMICS participants were analyzed (mean [SD] age, 64.5 [8.8] years; 1479 [78.9%] white; and 1013 [54.1%] male). In adjusted analysis, a 5-ppb (parts per billion) increase in ozone concentration was associated with a greater percentage of emphysema (β = 0.94; 95% CI, 0.25-1.64; P = .007) and percentage of air trapping (β = 1.60; 95% CI, 0.16-3.04; P = .03); worse scores for the mMRC Dyspnea Scale (β = 0.10; 95% CI, 0.03-0.17; P = .008), CAT (β = 0.65; 95% CI, 0.05-1.26; P = .04), and SGRQ (β = 1.47; 95% CI, 0.01-2.93; P = .048); lower FEV1% predicted value (β = -2.50; 95% CI, -4.42 to -0.59; P = .01); and higher odds of any exacerbation (odds ratio [OR], 1.37; 95% CI, 1.12-1.66; P = .002) and severe exacerbation (OR, 1.37; 95% CI, 1.07-1.76; P = .01). No association was found between historical ozone exposure and chronic bronchitis, COPD, airway wall thickness, or 6-minute walk test result.

Conclusions And Relevance: This study found that long-term historical ozone exposure was associated with reduced lung function, greater emphysema and air trapping on CT scan, worse patient-reported outcomes, and increased respiratory exacerbations for individuals with a history of heavy smoking. The association between ozone exposure and adverse respiratory outcomes suggests the need for continued reevaluation of ambient pollution standards that are designed to protect the most vulnerable members of the US population.
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January 2020

Quantifying the HIV treatment cascade in a South African health sub-district by gender: retrospective cohort study.

Trop Med Int Health 2020 02 21;25(2):186-192. Epub 2019 Nov 21.

Division of Social and Behavioural Sciences, School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa.

Objectives: To quantify the HIV care cascade in a Cape Town sub-district to understand rates of linkage to and engagement in HIV care.

Methods: We used routinely collected data to reconstruct the treatment cascade for 8382 infected individuals who tested HIV + in 2012/2013. We obtained data on patient gender, year of initial HIV-positive test, age at testing and initial CD4 cell count and defined five stages of the HIV care cascade. We quantified attrition across cascade stages.

Results: Two-thirds of the sample (5646) were women. Men were older at time of first testing (36.5 vs. 31.3 years) and had more advanced HIV disease at diagnosis (298 vs. 404 CD4 cells/µL for women). The median duration of follow-up was 818 days. Among women, 90.5% attended an initial HIV care visit, 54.6% became eligible for antiretroviral therapy under local guidelines during follow-up, 49.3% initiated ART and 45.6% achieved a therapeutic response. Among men, 88.0% attended an initial HIV care visit, 67.4% became ART eligible during follow-up, 48.0% initiated ART and 42.4% achieved a therapeutic response. Approximately 3% of women and 5% of men died during follow-up.

Conclusions: We were able to reconstruct the HIV treatment cascade using routinely collected data. In this setting, rates of engagement in care differ by gender in key stages of the cascade, with men faring worse than women at each cascade point. This highlights the need for interventions aimed at encouraging earlier testing, linkage, ART initiation and retention among men.
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February 2020

Association Between Long-term Exposure to Ambient Air Pollution and Change in Quantitatively Assessed Emphysema and Lung Function.

JAMA 2019 08;322(6):546-556

Department of Medicine, Columbia University Medical Center, New York, New York.

Importance: While air pollutants at historical levels have been associated with cardiovascular and respiratory diseases, it is not known whether exposure to contemporary air pollutant concentrations is associated with progression of emphysema.

Objective: To assess the longitudinal association of ambient ozone (O3), fine particulate matter (PM2.5), oxides of nitrogen (NOx), and black carbon exposure with change in percent emphysema assessed via computed tomographic (CT) imaging and lung function.

Design, Setting, And Participants: This cohort study included participants from the Multi-Ethnic Study of Atherosclerosis (MESA) Air and Lung Studies conducted in 6 metropolitan regions of the United States, which included 6814 adults aged 45 to 84 years recruited between July 2000 and August 2002, and an additional 257 participants recruited from February 2005 to May 2007, with follow-up through November 2018.

Exposures: Residence-specific air pollutant concentrations (O3, PM2.5, NOx, and black carbon) were estimated by validated spatiotemporal models incorporating cohort-specific monitoring, determined from 1999 through the end of follow-up.

Main Outcomes And Measures: Percent emphysema, defined as the percent of lung pixels less than -950 Hounsfield units, was assessed up to 5 times per participant via cardiac CT scan (2000-2007) and equivalent regions on lung CT scans (2010-2018). Spirometry was performed up to 3 times per participant (2004-2018).

Results: Among 7071 study participants (mean [range] age at recruitment, 60 [45-84] years; 3330 [47.1%] were men), 5780 were assigned outdoor residential air pollution concentrations in the year of their baseline examination and during the follow-up period and had at least 1 follow-up CT scan, and 2772 had at least 1 follow-up spirometric assessment, over a median of 10 years. Median percent emphysema was 3% at baseline and increased a mean of 0.58 percentage points per 10 years. Mean ambient concentrations of PM2.5 and NOx, but not O3, decreased substantially during follow-up. Ambient concentrations of O3, PM2.5, NOx, and black carbon at study baseline were significantly associated with greater increases in percent emphysema per 10 years (O3: 0.13 per 3 parts per billion [95% CI, 0.03-0.24]; PM2.5: 0.11 per 2 μg/m3 [95% CI, 0.03-0.19]; NOx: 0.06 per 10 parts per billion [95% CI, 0.01-0.12]; black carbon: 0.10 per 0.2 μg/m3 [95% CI, 0.01-0.18]). Ambient O3 and NOx concentrations, but not PM2.5 concentrations, during follow-up were also significantly associated with greater increases in percent emphysema. Ambient O3 concentrations, but not other pollutants, at baseline and during follow-up were significantly associated with a greater decline in forced expiratory volume in 1 second per 10 years (baseline: 13.41 mL per 3 parts per billion [95% CI, 0.7-26.1]; follow-up: 18.15 mL per 3 parts per billion [95% CI, 1.59-34.71]).

Conclusions And Relevance: In this cohort study conducted between 2000 and 2018 in 6 US metropolitan regions, long-term exposure to ambient air pollutants was significantly associated with increasing emphysema assessed quantitatively using CT imaging and lung function.
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August 2019

Projected Changes in Temperature-related Morbidity and Mortality in Southern New England.

Epidemiology 2018 07;29(4):473-481

Department of Epidemiology, Brown University School of Public Health, Providence, RI.

Background: Climate change is expected to result in more heat-related, but potentially fewer cold-related, emergency department visits and deaths. The net effect of projected changes in temperature on morbidity and mortality remains incompletely understood. We estimated the change in temperature-related morbidity and mortality at two sites in southern New England, United States, through the end of the 21st century.

Methods: We used distributed lag Poisson regression models to estimate the present-day associations between daily mean temperature and all-cause emergency department visits and deaths in Rhode Island and in Boston, Massachusetts. We estimated the change in temperature-related visits and deaths in 2045-2054 and 2085-2094 (relative to 2001-2010) under two greenhouse gas emissions scenarios (RCP4.5 and RCP8.5) using downscaled projections from an ensemble of over 40 climate models, assuming all other factors remain constant.

Results: We observed U-shaped relationships between temperature and morbidity and mortality in Rhode Island, with minima at 10.9°C and 22.5°C, respectively. We estimated that, if this population were exposed to the future temperatures projected under RCP8.5 for 2085-2094, there would be 5,976 (95% eCI = 1,630, 11,379) more emergency department visits but 218 (95% eCI = -551, 43) fewer deaths annually. Results were similar in Boston and similar but less pronounced in the 2050s and under RCP4.5.

Conclusions: We estimated that in the absence of further adaptation, if the current southern New England population were exposed to the higher temperatures projected for future decades, temperature-related emergency department visits would increase but temperature-related deaths would not.
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July 2018

Unconditional government cash transfers in support of orphaned and vulnerable adolescents in western Kenya: Is there an association with psychological wellbeing?

PLoS One 2017 31;12(5):e0178076. Epub 2017 May 31.

Academic Model Providing Access to Healthcare (AMPATH), Eldoret, Kenya.

Background: Orphaned and vulnerable adolescents (OVA) in sub-Saharan Africa are at greater risk for adverse psychological outcomes compared with their non-OVA counterparts. Social interventions that provide cash transfers (CTs) have been shown to improve health outcomes among young people, but little is known about their impact on the psychological wellbeing of OVA.

Objective: Among OVA in western Kenya, we assessed the association between living in a household that received monthly unconditional government CTs and psychological wellbeing.

Methods: We examined the likelihood of depression, anxiety, post-traumatic stress symptoms (PTSS) and positive future outlook among 655 OVA aged between 10 and 18 years who lived in 300 randomly selected households in western Kenya that either received or did not receive unconditional monthly CTs.

Results: The mean age was 14.0 (SD 2.4) years and 329 (50.2%) of the participants were female while 190 (29.0%) were double orphans whose biological parents were both deceased. After adjusting for socio-demographic, caregiver, and household characteristics and accounting for potential effects of participant clustering by sub-location of residence, OVA living in CT households were more likely to have a positive future outlook (odds ratio [OR] 1.47, 95% confidence interval [CI] 1.08, 1.99), less likely to be anxious (OR 0.57, 95% CI 0.42, 0.78), and less likely to have symptoms of post-traumatic stress (OR 0.50, 95% CI 0.29, 0.89). We did not find statistically significant differences in odds of depression by CT group.

Conclusion: OVA in CT households reported better psychological wellbeing compared to those in households not receiving CTs. CT interventions may be effective for improving psychological wellbeing among vulnerable adolescents in socioeconomically deprived households.
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September 2017

Effectiveness of peer-led interventions to increase HIV testing among men who have sex with men: a systematic review and meta-analysis.

AIDS Care 2017 08 2;29(8):1003-1013. Epub 2017 Feb 2.

a Department of Behavioural and Social Sciences , Brown University, School of Public Health , Providencike , USA.

HIV testing constitutes a key step along the continuum of HIV care. Men who have sex with men (MSM) have low HIV testing rates and delayed diagnosis, especially in low-resource settings. Peer-led interventions offer a strategy to increase testing rates in this population. This systematic review and meta-analysis summarizes evidence on the effectiveness of peer-led interventions to increase the uptake of HIV testing among MSM. Using a systematic review protocol that was developed a priori, we searched PubMed, PsycINFO and CINAHL for articles reporting original results of randomized or non-randomized controlled trials (RCTs), quasi-experimental interventions, and pre- and post-intervention studies. Studies were eligible if they targeted MSM and utilized peers to increase HIV testing. We included studies published in or after 1996 to focus on HIV testing during the era of combination antiretroviral therapy. Seven studies encompassing a total of 6205 participants met eligibility criteria, including two quasi-experimental studies, four non-randomized pre- and-post intervention studies, and one cluster randomized trial. Four studies were from high-income countries, two were from Asia and only one from sub-Saharan Africa. We assigned four studies a "moderate" methodological rigor rating and three a "strong" rating. Meta-analysis of the seven studies found HIV testing rates were statistically significantly higher in the peer-led intervention groups versus control groups (pooled OR 2.00, 95% CI 1.74-2.31). Among randomized trials, HIV testing rates were significantly higher in the peer-led intervention versus control groups (pooled OR: 2.48, 95% CI 1.99-3.08). Among the non-randomized pre- and post-intervention studies, the overall pooled OR for intervention versus control groups was 1.71 (95% CI 1.42-2.06), with substantial heterogeneity among studies (I= 70%, p < 0.02). Overall, peer-led interventions increased HIV testing among MSM but more data from high-quality studies are needed to evaluate effects of peer-led interventions on HIV testing among MSM in low- and middle-income countries.
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August 2017

Restless Legs Symptoms and Pregnancy and Neonatal Outcomes.

Clin Ther 2016 Feb 28;38(2):256-64. Epub 2015 Dec 28.

Department of Medicine, The Warren Alpert Medical School of Brown University, The Miriam Hospital, Providence, Rhode Island. Electronic address:

Purpose: Restless legs syndrome (RLS) is a commonly occurring neurologic disorder that affects up to one third of women during pregnancy. RLS has been associated with increased sympathetic tone in the nonpregnant population. We examined whether a RLS surrogate is associated with a higher prevalence of pregnancy and neonatal outcomes.

Methods: Data were analyzed from a cross-sectional survey of 1000 women interviewed soon after delivery by using an RLS surrogate question. Women were asked how frequently (0 = none, 1 = rarely [<1 time/week], 2 = sometimes [1-2 times/week], 3 = frequently [3-4 times/week], and 4 = always [5-7 times/week]) they had "experienced jumpy or jerky leg movements" in the last 3 months of pregnancy. Clinical charts were reviewed to obtain relevant demographic and clinical data, including the presence of gestational hypertensive disorders and neonatal outcomes at birth. Subjects who "always" experienced RLS were compared with subjects experiencing symptoms less frequently or not at all with respect to prevalence of gestational hypertensive disorder.

Findings: The mean ([SD]) age, prepregnancy body mass index (BMI), and BMI at delivery were 29.0 (6.1) years, 26.1 (6.2) kg/m(2), and 32.0 (6.3) kg/m(2), respectively. The overall prevalence of the RLS surrogate (jumpy or jerky leg movements) was 35.5% with the following distribution on a Likert scale: score 1 = 6.4%; score 2 = 10.2%; score 3 = 8.1%; and score 4 = 10.8%. Chronic hypertension was present in 2.1%, pregnancy-induced hypertension in 9.5%, and preeclampsia in 4.5% of respondents. Subjects who reported "always" having sensations of jumpy or jerky legs were more likely to have gestational hypertensive disorders compared with those who reported less frequent occurrence of the symptoms. Adjusted odds ratios were 3.74 (95% CI, 1.31-10.72; P = 0.014) for chronic hypertension; 1.26 (95% CI, 0.65-2.46; P = 0.487) for pregnancy-induced hypertension; and 2.15 (95% CI, 0.97-4.75; P = 0.060) for preeclampsia. There was a significant association between leg movement score and neonatal birth weight (coefficient, -149.5 g [95% CI, -276.9 to -22.5]; P = 0.005) and gestational age at birth (-0.7 week [95% CI, -1.1 to -0.2]; P = 0.021) that persisted after adjusting for preeclampsia, diabetes, and smoking.

Implications: A higher frequency of jumpy or jerky leg symptoms, a proxy for RLS during pregnancy, was associated with a higher likelihood of gestational hypertensive disorders and neonatal outcomes such as gestational age at birth and birth weight. These findings may affect RLS treatment decisions during pregnancy.
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February 2016

Residential proximity to major roadways and prevalent hypertension among postmenopausal women: results from the Women's Health Initiative San Diego Cohort.

J Am Heart Assoc 2014 Oct 1;3(5):e000727. Epub 2014 Oct 1.

Department of Epidemiology, Brown University School of Public Health, Providence, RI (K.K., M.N.E., Y.W., C.B.E., G.A.W.).

Background: Living near major roadways has been linked with increased risk of cardiovascular events and worse prognosis. Residential proximity to major roadways may also be associated with increased risk of hypertension, but few studies have evaluated this hypothesis.

Methods And Results: We examined the cross-sectional association between residential proximity to major roadways and prevalent hypertension among 5401 postmenopausal women enrolled into the San Diego cohort of the Women's Health Initiative. We used modified Poisson regression with robust error variance to estimate the association between prevalence of hypertension and residential distance to nearest major roadway, adjusting for participant demographics, medical history, indicators of individual and neighborhood socioeconomic status, and for local supermarket/grocery and fast food/convenience store density. The adjusted prevalence ratios for hypertension were 1.22 (95% CI: 1.07, 1.39), 1.13 (1.00, 1.27), and 1.05 (0.99, 1.12) for women living ≤100, >100 to 200, and >200 to 1000 versus >1000 m from a major roadway (P for trend=0.006). In a model treating the natural log of distance to major roadway as a continuous variable, a shift in distance from 1000 to 100 m from a major roadway was associated with a 9% (3%, 16%) higher prevalence of hypertension.

Conclusions: In this cohort of postmenopausal women, residential proximity to major roadways was positively associated with the prevalence of hypertension. If causal, these results suggest that living close to major roadways may be an important novel risk factor for hypertension.
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October 2014

High burden of STIs among HIV-infected adults prior to initiation of ART in South Africa: a retrospective cohort study.

Sex Transm Infect 2014 Dec 16;90(8):615-9. Epub 2014 May 16.

Health Systems Research Unit, South African Medical Research Council; and the School of Public Health and Family Medicine, University of Cape Town, Cape Town, South Africa.

Objectives: To assess the burden of sexually transmitted infections (STIs) among HIV-positive South Africans in the period prior to antiretroviral therapy (ART) initiation compared with the period once on ART.

Methods: We linked the clinic records of 1465 patients currently on ART to the electronic database which records all visits to city clinics. We used a mixed effects Poisson model to assess the relative rates of occurrence of treatment seeking for an STI in the periods prior to initiation of ART and while on ART.

Results: We accumulated 4214 person-years of follow-up, divided nearly equally between the pre-ART and on-ART periods. The rate of treatment seeking for new STIs was 5.50 (95% CI 5.43 to 5.78) per 100 person-years, and individuals had on average a sevenfold higher rate of seeking treatment for STIs in the period prior to initiating ART (9.57 per 100 person-years) compared with the period once on ART (5.5 per 100 person-years) (adjusted rate ratio (RR) 7.01, 95% CI 4.64 to 10.59). Being male (RR 1.73, 95% CI 1.18 to 2.55) or younger (age <25) (RR 2.67, 95% CI 1.53 to 4.65) was associated with higher incidence of clinic visits for STI treatment, while advanced stage of HIV disease (WHO stage 4) (RR 0.33, 95% CI 0.15 to 0.69) was associated with lower incidence.

Conclusions: The period prior to the initiation of ART is a critical period where increased attention should be focused on the detection and treatment of STIs. A successful effort to treat STIs in this period will likely reduce further HIV transmission and fits within a test-and-treat approach.
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December 2014

Renal disease in an antiretroviral-naïve HIV-infected outpatient population in Western Kenya.

Nephrol Dial Transplant 2007 Aug;22(8):2208-12

Indiana University School of Medicine, Indianapolis, IN 46202, USA.

Background: Several commonly used antiretrovirals (ARVs) require dose adjustments to prevent toxicities in the presence of renal insufficiency. Because no prospective studies of the prevalence or risk factors for kidney disease in stable outpatient human immunodeficiency virus (HIV)-infected indigenous African populations have been published to date, it is not known if already scarce resources should be allocated to detect renal dysfunction, in those without risk factors for kidney disease, prior to initiation of increasingly available antiretrovirals in developing countries.

Methods: A cross-sectional study to determine the prevalence of and risk factors for renal disease in a cohort of medically stable, HIV-infected, antiretroviral-naïve adults, without diabetes or hypertension, presenting to an HIV clinic in western Kenya.

Results: Of 373 patients with complete data, renal insufficiency (CrCl <60 ml/min) was identified in 43 (11.5%) [18 (4.8%) had a CrCl <50 ml/min]. Despite high correlation coefficients between the three renal function estimating equations used, when compared to creatinine clearance as calculated by Cockcroft-Gault, lower rates of moderate to severe renal insufficiency were identified by the Modification of Diet in Renal Disease equations. Proteinuria, defined as a urine dipstick protein of equal to or greater than 1+, was detected in only 23 subjects (6.2%).

Conclusions: Renal insufficiency is not uncommon, even in stable patients without diabetes or hypertension. Conversely, proteinuria was unexpectedly infrequent in this population. Utilizing resources to assess renal function prior to initiation of antiretrovirals in order to identify those likely to benefit from dosage adjustment is justified.
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August 2007