Total blood mercury levels and depression among adults in the United States: National Health and Nutrition Examination Survey 2005-2008.

BACKGROUND: Mercury is a neurotoxicant linked with psychiatric symptoms at high levels of exposure. However, it is unclear whether an association is present at the low exposure levels in the US adult population. MATERIALS AND METHODS: Cross-sectional associations of total blood mercury and depression were assessed in 6,911 adults age ≥20 in the National Health and Nutrition Examination Survey (NHANES), 2005-2008. The Patient Health Questionnaire-9 was used to assess depression (high likelihood of a depressive spectrum disorder diagnosis; score 5-27). RESULTS: Unadjusted survey weighted logistic regression suggested that higher total blood mercury was associated with lower odds of depression (Odds Ratio  = 0.49, 95% Confidence Interval: 0.36-0.65, comparing the highest and lowest mercury quintiles). This association largely disappeared after adjustment for sociodemographic variables (income-poverty ratio, education, marital status). However, in age-stratified analyses, this inverse relationship remained in older adults (age ≥40) even after adjustment for sociodemographic variables. Simulation analyses adjusting for expected confounding effects of fish intake suggested that the inverse relationship among older adults may be plausibly attributed to residual confounding (Odds Ratio  = 0.75, 95% Confidence Interval: 0.50-1.12, comparing the highest and lowest mercury quintiles). CONCLUSIONS: Higher total blood mercury was not associated with increased odds of depression. The lower odds of depression in older adults with higher total blood mercury may be due to residual confounding

Study Population and Inclusion/Exclusion Criteria, NHANES, United States, 2005–2008.

<p>Abbreviations: NHANES–National Health and Nutrition Examination Survey; PHQ-9–Patient Health Questionnaire-9. Covariates included age, sex, race/ethnicity, family income-poverty ratio, educational attainment, marital status, current smoking status, self-reported drinking, body mass index, self-reported past 30 days fish intake, and past 24 hours polyunsaturated fatty acid intake. Percentages represented the percentages of individuals among the whole sample.</p

Descriptive Statistics of the Study Population, NHANES, United States, 2005–2008.^a

<p>Abbreviations: DHA–Docosahexaenoic Acid; EPA–Eicosapentaenoic Acid; IQR–interquartile range; NHANES–National Health and Nutrition Examination Survey; PHQ-9–Patient Health Questionnaire-9.</p><p>*<i>P</i><0.05 for design-adjusted chi-square statistics based on weighted frequencies, comparing proportions between younger older adults.</p>a<p>All proportions were calculated based on weighted frequencies; the frequencies presented here represented the sizes of the unweighted sample.</p>b<p>Quantiles were generated based on the weighted sample. Chi-square tests were not performed for variables with quantiles. Quantile upper bounds (from left to right: quantile 1–5, respectively): Total blood mercury (µg/L)–whole sample: 0.5, 0.8, 1.3, 2.3, 38.7; younger adults: 0.4, 0.7, 1.1, 2.1, 23.8; older adults: 0.5, 0.9, 1.4, 2.5, 38.7; Family income-poverty ratio–whole sample: 1.4, 2.6, 4.0, <5.0, 5.0; younger adults: 1.2, 2.1, 3.5, <5.0, 5.0; older adults: 1.6, 2.9, 4.5, <5.0, 5.0; Past 24 hours EPA intake (gram)–whole sample: 0.001, 0.011, 2.589; younger adults: 0.001, 0.010, 2.589; older adults: 0.001, 0.012, 2.422; Past 24 hours DHA intake (gram)–whole sample: 0.005, 0.046, 6.390; younger adults: 0.004, 0.041, 6.390; older adults: 0.006, 0.047, 3.389.</p>c<p>Note that the disproportional distribution of quintiles for income-poverty ratio was because all individuals in the 5^th quintile had the maximum value of 5.</p

Contact tracing for the control of infectious disease epidemics: Chronic Wasting Disease in deer farms

Contact tracing is a crucial component of the control of many infectious diseases, but is an arduous and time consuming process. Procedures that increase the efficiency of contact tracing increase the chance that effective controls can be implemented sooner and thus reduce the magnitude of the epidemic. We illustrate a procedure using Graph Theory in the context of infectious disease epidemics of farmed animals in which the epidemics are driven mainly by the shipment of animals between farms. Specifically, we created a directed graph of the recorded shipments of deer between deer farms in Pennsylvania over a timeframe and asked how the properties of the graph could be exploited to make contact tracing more efficient should Chronic Wasting Disease (a prion disease of deer) be discovered in one of the farms. We show that the presence of a large strongly connected component in the graph has a significant impact on the number of contacts that can arise. Keywords: Chronic Wasting Disease, Contact tracing, Directed graphs, Strongly connected component

Work Characteristics Associated with Physical Functioning in Women.

Women make up almost half of the labor force with older women becoming a growing segment of the population. Work characteristics influence physical functioning and women are at particular risk for physical limitations. However, little research has explored the effects of work characteristics on women's physical functioning. U.S. women between the ages of 50 and 79 were enrolled in the Women's Health Initiative Observational Study between 1993 and 1998. Women provided job titles and years worked at their three longest-held jobs (n = 79,147). Jobs were linked to characteristics in the Occupational Information Network. Three categories of job characteristics related to substantive complexity, physical demand, and social collaboration emerged. The association between job characteristics and physical limitations in later life, measured using a SF-36 Physical Functioning score &lt;25th percentile, was examined using modified Poisson regression. After controlling for confounding variables, high physical demand was positively associated with physical limitations (RR = 1.09 CI: 1.06-1.12) and substantively complex work was negatively associated (RR = 0.94, CI: 0.91-0.96). Jobs requiring complex problem solving, active learning, and critical thinking were associated with better physical functioning. Employers should explore opportunities to reduce strain from physically demanding jobs and incorporate substantively complex tasks into women's work to improve long-term health