Objective and sources: We reviewed the epidemiologic literature for PFOA. Data synthesis: Perfluorooctanoic acid (PFOA) does not occur naturally but is present in the serum of most residents of ...industrialized countries (U.S. median, 4 ng/mL). Drinking water is the primary route of exposure in some populations, but exposure sources are not well understood. PFOA has been used to manufacture such products as Gore-Tex and Teflon. PFOA does not break down in the environment; the human half-life is estimated at about 3 years. PFOA is not metabolized in the body; it is not lipophilic. PFOA is not directly genotoxic; animal data indicate that it can cause several types of tumors and neonatal death and may have toxic effects on the immune, liver, and endocrine systems. Data on the human health effects of PFOA are sparse. There is relatively consistent evidence of modest positive associations with cholesterol and uric acid, although the magnitude of the cholesterol effect is inconsistent across different exposure levels. There is some but much less consistent evidence of a modest positive correlation with liver enzymes. Most findings come from cross-sectional studies, limiting conclusions. Two occupational cohort studies do not provide consistent evidence for chronic disease; both are limited by sample size and reliance on mortality data. Reproductive data have increased recently but are inconsistent, and any observed adverse effects are modest. Conclusions: Epidemiologic evidence remains limited, and to date data are insufficient to draw firm conclusions regarding the role of PFOA for any of the diseases of concern.
Abstract
Epidemiologic evidence is often a key source of information used by expert committees to guide policy decisions, yet epidemiologists rarely consider this audience for their research. For a ...better understanding of the pipeline from epidemiologic research to expert committee assessment to policy, several reports from the National Academies of Sciences, Engineering, and Medicine were reviewed and discussed with staff and committee members. The topics of these consensus committee assessments included health behaviors, medical care, and military exposures. The focus was often on emerging issues of immediate concern for which there was little relevant research available but a need for prompt action. Committees generally sought a comprehensive assessment of potential health effects of a given product or exposure, which often included social and behavioral health outcomes that are rarely addressed by epidemiologists. To enhance epidemiology’s contribution to societal decisions, the choice of research topics should expand to consider emerging societal concerns. Research funding agencies need to be engaged as mediators between committee needs and the research community to stimulate contributory research. Improved communication of research needs to the epidemiology community would be beneficial to researchers aspiring to have an impact and to those who use epidemiologic information to help guide policy decisions.
Background
Postpartum depression (PPD) can result in negative personal and child developmental outcomes. Only a few large population‐based studies of PPD have used clinical diagnoses of depression ...and no study has examined how a maternal depression history interacts with known risk factors. The objective of this study was to examine the impact of a depression history on PPD and pre‐ and perinatal risk factors.
Methods
A nationwide prospective cohort study of all women with live singleton births in Sweden from 1997 through 2008 was conducted. Relative risk (RR) of clinical depression within the first year postpartum and two‐sided 95% confidence intervals were estimated.
Results
The RR of PPD in women with a history of depression was estimated at 21.03 (confidence interval: 19.72–22.42), compared to those without. Among all women, PPD risk increased with advanced age (1.25 (1.13–1.37)) and gestational diabetes (1.70 (1.36–2.13)). Among women with a history of depression, pregestational diabetes (1.49 (1.01–2.21)) and mild preterm delivery also increased risk (1.20 (1.06–1.36)). Among women with no depression history, young age (2.14 (1.79–2.57)), undergoing instrument‐assisted (1.23 (1.09–1.38)) or cesarean (1.64(1.07–2.50)) delivery, and moderate preterm delivery increased risk (1.36 (1.05–1.75)). Rates of PPD decreased considerably after the first postpartum month (RR = 0.27).
Conclusion
In the largest population‐based study to date, the risk of PPD was more than 20 times higher for women with a depression history, compared to women without. Gestational diabetes was independently associated with a modestly increased PPD risk. Maternal depression history also had a modifying effect on pre‐ and perinatal PPD risk factors.
Abstract
Cross-sectional studies—often defined as those in which exposure and outcome are assessed at the same point in time—are frequently viewed as minimally informative for causal inference. While ...cross-sectional studies may be susceptible to reverse causality, may be limited to assessment of disease prevalence rather than incidence, or may only provide estimates of current rather than past exposures, not all cross-sectional studies suffer these limitations. Moreover, none of these concerns are unique to or inherent in the structure of a cross-sectional study. Regardless of when exposure and disease were ascertained relative to one another, a cross-sectional study may provide insights into the causal effects of exposure on disease incidence. Simply labeling a study as “cross-sectional” and assuming that 1 or more of these limitations exist and are materially important fails to recognize the need for a more nuanced assessment and risks discarding evidence that may be useful in assessing causal relationships.
Interpreting the results of epidemiologic studies calls for objectivity and rigorous scrutiny, acknowledging the limitations that temper the applicability of the findings to public health action. ...Current trends have posed new challenges to balancing goals of scientific objectivity and validity with public health applications. The ongoing tension between epidemiology’s aspirations and capability has several sources: the need to overpromise in research proposals, compromising methodological rigor because of public health importance, defending findings in the face of hostile critics, and appealing to core constituencies who have specific expectations from the research.
Abstract
Harlow et al. (Am J Epidemiol. 2021;190(3):353–361) are among the first to tackle the complex subject of electronic cigarette use and reproductive health, focused on fecundity but pertinent ...to the full spectrum of reproductive health concerns. Despite extensive documentation of the health harm from tobacco use and a shared exposure to nicotine, electronic cigarette (e-cigarette) users have a markedly different exposure profile. Because e-cigarettes might help to curtail or eliminate tobacco smoking, the health comparisons of interest for e-cigarettes should include cigarette smoking as well as no use of such products. These researchers confront significant methodological challenges in the study of reproductive health effects of e-cigarettes: addressing confounding with little information on the characteristics of e-cigarette users, a complex connection between e-cigarette and tobacco use, multiple and poorly understood exposure to e-cigarette vapors, and lack of a standard method for quantifying exposure. Evidence is urgently needed to inform regulation and individual decisions regarding the use of this potentially harmful product that might well entice new users of nicotine, some of whom progress to tobacco use, but that also has the potential to enable otherwise recalcitrant smokers to substitute a less harmful product.
•Evidence supports an association between PFOA and kidney and testicular cancer.•Consistent evidence for a link with cholesterol, but not with heart disease.•Suggestive evidence for a link between ...PFOA and ulcerative colitis.•A link with liver and immune function but little link for liver or infectious disease.•A possible link with low birthweight may be due to reverse causality or confounding.
The C8 Science Panel was composed of three epidemiologists charged with studying the possible health effects of PFOA in a highly exposed population in the mid-Ohio Valley. The Panel determined in 2012 there was a ‘probable link’ (i.e., more probable than not based on the weight of the available scientific evidence) between PFOA and high cholesterol, thyroid disease, kidney and testicular cancer, pregnancy-induced hypertension, and ulcerative colitis.
Here, former C8 Science Panel members and collaborators comment on the PFOA literature regarding thyroid disorders, cancer, immune and auto-immune disorders, liver disease, hypercholesterolemia, reproductive outcomes, neurotoxicity, and kidney disease. We also discuss developments regarding fate and transport, and pharmacokinetic models, and discuss causality assessment in cross-sectional associations among low-exposed populations.
For cancer, the epidemiologic evidence remains supportive but not definitive for kidney and testicular cancers. There is consistent evidence of a positive association between PFOA and cholesterol, but no evidence of an association with heart disease. There is evidence for an association with ulcerative colitis, but not for other auto-immune diseases. There is good evidence that PFOA is associated with immune response, but uneven evidence for an association with infectious disease. The evidence for an association between PFOA and thyroid and kidney disease is suggestive but uneven. There is evidence of an association with liver enzymes, but not with liver disease. There is little evidence of an association with neurotoxicity. Suggested reductions in birthweight may be due to reverse causality and/or confounding. Fate and transport models and pharmacokinetic models remain central to estimating past exposure for new cohorts, but are difficult to develop without good historical data on emissions of PFOA into the environment.
Overall, the epidemiologic evidence remains limited. For a few outcomes there has been some replication of our earlier findings. More longitudinal research is needed in large populations with large exposure contrasts. Additional cross-sectional studies of low exposed populations may be less informative.
Rising temperatures and heatwaves increase mortality. Many of the subpopulations most vulnerable to heat-related mortality are in prisons, facilities that may exacerbate temperature exposures. Yet, ...there is scare literature on the impacts of heat among incarcerated populations. We analyzed data on mortality in U.S. state and private prisons from 2001-2019 linked to daily maximum temperature data for the months of June, July, and August. Using a case-crossover approach and distributed lag models, we estimated the association of increasing temperatures with total mortality, heart disease-related mortality, and suicides. We also examined the association with extreme heat and heatwaves (days above the 90th percentile for the prison location) and assessed effect modification by personal, facility, and regional characteristics. There were 12,836 deaths during summer months. The majority were male (96%) and housed in a state-operated prison (97%). A 10°F increase was associated with a 5.2% (95% CI: 1.5%, 9.0%) increase in total mortality and a 6.7% (95% CI: -0.6%, 14.0%) increase in heart disease mortality. The association between temperature and suicides was delayed, peaking around lag 3 (exposure at three days prior death). Two- and three-day heatwaves were associated with increased total mortality of 5.5% (95% CI: 0.3%, 10.9%) and 7.4% (95% CI: 1.6%, 13.5%), respectively. The cumulative effect (lags 1-3) of an extreme heat day was associated with a 22.8% (95% CI: 3.3%, 46.0%) increase in suicides. We found the greatest increase in mortality among people ≥ 65 years old, incarcerated less than one year, held in the Northeast region, and in urban or rural counties. These findings suggest that warm temperatures are associated with increased mortality in prisons, yet this vulnerable population's risk has largely been overlooked.
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