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In this paper, we examine patterns of self-reported diagnosis of noncommunicable diseases (NCDs) and prevalences of algorithm/measured test-based, undiagnosed, and untreated NCDs in China, Ghana, India, Mexico, Russia, and South Africa. Nationally representative samples of older adults aged ≥50 years were analyzed from wave 1 of the World Health Organization's Study on Global Ageing and Adult Health (2007-2010; n = 34,149). Analyses focused on 6 conditions: angina, arthritis, asthma, chronic lung disease, depression, and hypertension. Outcomes for these NCDs were: 1) self-reported disease, 2) algorithm/measured test-based disease, 3) undiagnosed disease, and 4) untreated disease. Algorithm/measured test-based prevalence of NCDs was much higher than self-reported prevalence in all 6 countries, indicating underestimation of NCD prevalence in low- and middle-income countries. Undiagnosed prevalence of NCDs was highest for hypertension, ranging from 19.7% (95% confidence interval (CI): 18.1, 21.3) in India to 49.6% (95% CI: 46.2, 53.0) in South Africa. The proportion untreated among all diseases was highest for depression, ranging from 69.5% (95% CI: 57.1, 81.9) in South Africa to 93.2% (95% CI: 90.1, 95.7) in India. Higher levels of education and wealth significantly reduced the odds of an undiagnosed condition and untreated morbidity. A high prevalence of undiagnosed NCDs and an even higher proportion of untreated NCDs highlights the inadequacies in diagnosis and management of NCDs in local health-care systems. [ABSTRACT FROM AUTHOR]

In several studies of antiretroviral treatment (ART) programs for persons with human immunodeficiency virus infection, investigators have reported that there has been a higher rate of loss to follow-up (LTFU) among patients initiating ART in recent years than among patients who initiated ART during earlier time periods. This finding is frequently interpreted as reflecting deterioration of patient retention in the face of increasing patient loads. However, in this paper we demonstrate by simulation that transient gaps in follow-up could lead to bias when standard survival analysis techniques are applied. We created a simulated cohort of patients with different dates of ART initiation. Rates of ART interruption, ART resumption, and mortality were assumed to remain constant over time, but when we applied a standard definition of LTFU, the simulated probability of being classified LTFU at a particular ART duration was substantially higher in recently enrolled cohorts. This suggests that much of the apparent trend towards increased LTFU may be attributed to bias caused by transient interruptions in care. Alternative statistical techniques need to be used when analyzing predictors of LTFU—for example, using “prospective” definitions of LTFU in place of “retrospective” definitions. Similar considerations may apply when analyzing predictors of LTFU from treatment programs for other chronic diseases. [ABSTRACT FROM PUBLISHER]

Spatial statistical analysis of 1994-1995 small-area malaria incidence rates in the population of the northernmost districts of KwaZulu Natal, South Africa, was undertaken to identify factors that might explain very strong heterogeneity in the rates. In this paper, the authors describe a method of adjusting the regression analysis results for strong spatial correlation in the rates by using generalized linear mixed models and variograms. The results of the spatially adjusted, multiple regression analysis showed that malaria incidence was significantly positively associated with higher winter rainfall and a higher average maximum temperature and was significantly negatively associated with increasing distance from water bodies. The statistical model was used to produce a map of predicted malaria incidence in the area, taking into account local variation from the model prediction if this variation was supported by the data. The predictor variables showed that even small differences in climate can have very marked effects on the intensity of malaria transmission, even in areas subject to malaria control for many years. The results of this study have important implications for malaria control programs in the area. Am J Epidemiol 2001;153:1213-21. [ABSTRACT FROM AUTHOR]

Respondent-driven sampling (RDS) is a potential strategy for addressing challenges in accurate estimation of abortion incidence, but it relies on often untested assumptions. We conducted an RDS study to estimate the cumulative lifetime incidence of abortion in Soweto, Johannesburg, South Africa (April–December 2018), to evaluate whether RDS assumptions were met, and to compare RDS estimates of incidence with estimates adjusted for employment and age based on census data. A total of 849 participants were recruited from 11 seed participants between April and December 2018. The assumption that individuals can identify target population members and the assumption of approximation of sampling with replacement was met. There were minor violations of the assumptions of seed independence from the final sample and reciprocity of ties. Assumptions of accurate degree reporting and random recruitment were not met. Failure to meet assumptions yielded a study sample with different employment characteristics than those of the target population; this could not be resolved by standard RDS methods. The RDS estimate of cumulative lifetime abortion incidence was 12.1% (95% confidence interval: 9.8, 14.3), and the employment-adjusted estimate was 16.9% (95% confidence interval: 12.8, 22.1). We caution researchers in using RDS for representative estimates of abortion incidence. Use of postsurvey weights to adjust for differences in characteristics between the sample and the target population may yield more representative results. [ABSTRACT FROM AUTHOR]

Although effective in controlling malaria, indoor residual spraying results in elevated exposure to insecticides such as dichlorodiphenyltrichloroethane (DDT) and pyrethroids. These chemicals cross the placenta, but no studies have examined their associations with birth outcomes in populations residing in indoor residual spraying areas. We investigated this question in the Venda Health Examination of Mothers, Babies and Their Environment (VHEMBE), a birth cohort study of 751 South African children born between 2012 and 2013. We measured maternal peripartum serum DDT and urine pyrethroid metabolite concentrations and collected data on birth weight, length, head circumference, and duration of gestation. We analyzed the data using marginal structural models with inverse-probability-of-treatment weights, generalized propensity scores, and standard conditional linear regression. Using all 3 analytical methods, p,p ′-DDT, o,p ′-DDT, and to a lesser extent p,p ′-dichlorodiphenyldichloroethylene were related to elevated birth weight, birth length, and head circumference among girls. Changes in gestational duration did not mediate this relationship, suggesting that these exposures accelerate fetal growth, which is consistent with the known estrogenic properties of o,p ′-DDT and p,p ′-DDT. No associations with pyrethroid metabolites were found. Results suggest that prenatal exposure to DDT is related to elevated birth size. Further studies are needed to elucidate the implications of these findings. [ABSTRACT FROM AUTHOR]

Estimation of causal effects from observational data is a primary goal of epidemiology. The use of multiple methods with different assumptions relating to exchangeability improves causal inference by demonstrating robustness across assumptions. We estimated the effect of antiretroviral therapy (ART) on mortality in rural KwaZulu-Natal, South Africa, from 2007 to 2011, using 2 methods with substantially different assumptions: the regression discontinuity design (RDD) and inverse-probability–weighted (IPW) marginal structural models (MSMs). The RDD analysis took advantage of a CD4-cell-count–based threshold for ART initiation (200 cells/μL). The 2 methods yielded consistent but nonidentical results for the effect of immediate initiation of ART (RDD intention-to-treat hazard ratio (HR) = 0.66, 95% confidence interval (CI): 0.35, 1.26; RDD complier average causal effect HR = 0.56, 95% CI: 0.41, 0.77; IPW MSM HR = 0.49, 95% CI: 0.42, 0.58). Although RDD and IPW MSM estimates have distinct identifying assumptions, strengths, and limitations in terms of internal and external validity, results in this application were similar. The differences in modeling approaches and the external validity of each method may explain the minor differences in effect estimates. The overall consistency of the results lends support for causal inference about the effect of ART on mortality from these data. [ABSTRACT FROM AUTHOR]

Many epidemiologic studies identify contrasts between an “always-exposed” population and a “never-exposed” population. Such “exposure effects” are perhaps most valuable in discussing individual lifestyle changes, or in clinical care; they may be less valuable in estimating the potential effects of realistic public health interventions. Various methods, among them population attributable fractions and generalized impact fractions, attempt to obtain more policy-relevant estimates of “population intervention” effects, but such methods remain rare in the epidemiologic literature. Here, we describe the use of the parametric g-formula as a tool for the estimation of population intervention effects in longitudinal data. Our discussion is motivated by a previous study of the effect of incident pregnancy on time to virological failure among human immunodeficiency virus-positive women initiating antiretroviral therapy in South Africa between 2004 and 2011. We show that 1) interventional estimates of effect can be estimated in longitudinal data using the parametric g-formula and 2) exposure effects and population interventional effects can have dramatically different interpretations and magnitudes in real-world data. Epidemiologists should consider estimating interventional effects in addition to exposure effects; doing so would allow the results of epidemiologic studies to be more immediately relevant to policy-makers and to implementation science efforts. [ABSTRACT FROM AUTHOR]

A prospective survey of social mixing patterns relevant to respiratory disease transmission by large droplets (e.g., influenza) or small droplet nuclei (e.g., tuberculosis) was performed in a South African township in 2010. A total of 571 randomly selected participants recorded the numbers, times, and locations of close contacts (physical/nonphysical) and indoor casual contacts met daily. The median number of physical contacts was 12 (interquartile range (IQR), 7–18), the median number of close contacts was 20 (IQR, 13–29), and the total number of indoor contacts was 30 (IQR, 12–54). Physical and close contacts were most frequent and age-associative in youths aged 5–19 years. Numbers of close contacts were 40% higher than in corresponding populations in industrialized countries (P < 0.001). This may put township communities at higher risk for epidemics of acute respiratory illnesses. Simulations of an acute influenza epidemic predominantly involved adolescents and young adults, indicating that control strategies should be directed toward these age groups. Of all contacts, 86.2% occurred indoors with potential exposure to respiratory droplet nuclei, of which 27.2%, 20.1%, 20.0%, and 8.0% were in transport, own household, crèche/school, and work locations, respectively. Indoor contact time was long in households and short during transport. High numbers of indoor contacts and intergenerational mixing in households and transport may contribute to exceptionally high rates of tuberculosis transmission reported in the community. [ABSTRACT FROM AUTHOR]

Cross-sectional studies have suggested that intravaginal practices, such as douching or “dry sex,” may increase women's susceptibility to infection with human immunodeficiency virus (HIV). The authors examined the temporal nature of this association in a cohort of South African women. At enrollment (2001–2002), 4,089 women were tested for HIV infection. Participants reported their intravaginal practices at a 6-month follow-up visit and were followed with repeat HIV testing for up to 24 months. Among the 3,570 women who were HIV-negative at enrollment, 26% reported some type of intravaginal practice, mostly washing inside the vagina with water and/or cloth as part of daily hygiene. During follow-up, 85 incident HIV infections were observed. Intravaginal practices were associated with prevalent HIV at enrollment (adjusted odds ratio = 1.50, 95% confidence interval: 1.22, 1.85), but during follow-up there was no association between intravaginal practices and incident HIV (adjusted hazard ratio = 1.04, 95% confidence interval: 0.65, 1.68). These findings may be explained by a reversal of the causal sequence assumed for this association, since intravaginal practices may be undertaken in response to vaginal infections that occur more commonly among HIV-infected women. Intravaginal practices appear unlikely to be a cofactor in the male-to-female transmission of HIV in this setting. [ABSTRACT FROM AUTHOR]

Gender-based violence is a key health risk for women globally and in South Africa. The authors analyzed data from 1,395 interviews with women attending antenatal clinics in Soweto, South Africa, between November 2001 and April 2002 to estimate the prevalence of physical/sexual partner violence (55.5%), adult sexual assault by nonpartners (7.9%), child sexual assault (8.0%), and forced first intercourse (7.3%). Age at first experience of each type of violence was modeled by the Kaplan-Meier method, and Cox hazard models with time-varying covariates were used to explore whether child sexual assault and forced first intercourse were associated with risk of violent revictimization in adulthood. Child sexual assault was associated with increased risk of physical and/or sexual partner violence (risk ratio = 2.43, 95% confidence interval: 1.93, 3.06) and with adult sexual assault by a nonpartner (risk ratio = 2.33, 95% confidence interval: 1.40, 3.89). Forced first intercourse was associated with increased risk of physical and/or sexual partner violence (risk ratio = 2.64, 95% confidence interval: 2.07, 3.38) and nonsignificantly with adult sexual assault by a nonpartner (risk ratio = 2.14, 95% confidence interval: 0.92, 4.98). This study confirms the need for increased attention by the public health community to primary and secondary prevention of gender-based violence, with a specific need to reduce risk among South African adolescents. [ABSTRACT FROM AUTHOR]

An obituary for epidemiologist Dr. Mervyn Susser is presented.