On influencing population means

Predicting the Population Health Impacts of Community Interventions: The Case of Alcohol Outlets and Binge Drinking

A substitution estimator can be used to predict how shifts in population exposures might change health. We illustrated this method by estimating how an upper limit on alcohol outlet density might alter binge drinking in the New York Social Environment Study (n = 4000), and provided statistical code and sample data. The largest differences in binge drinking were for an upper limit of 70 outlets per square mile; there was a -0.7% difference in binge drinking prevalence for New York City overall (95% confidence interval [CI] = -0.2%, -1.3%) and a -2.4% difference in binge drinking prevalence for the subset of communities the intervention modified (95% CI = -0.5%, -4.0%). A substitution estimator is a flexible tool for estimating population intervention parameters and improving the translation of public health research results to practitioners.

Invited commentary: sleep disturbances--another threat to male fecundity?

In a cross-sectional study among 953 young Danish men (2008-2011), Jensen et al. reported that sleep disturbances showed inverse U-shaped associations with semen parameters and testis size (Am J Epidemiol. 2013;177(10):1027-1037). Sleep disturbances were associated with several factors likely to affect semen parameters (such as history of sexually transmitted infections) that cannot all be efficiently controlled for, leaving room for residual confounding. Future studies could adopt a longitudinal design and rely on objective personal measures of sleep quality and duration using accelerometers. Intervention studies would also be helpful to identify whether sleep disturbances (or improvement of sleep quality) can lead to short-term variations in semen parameters. This study adds another suspect to the list of factors possibly influencing male fecundity potential, which also includes overweight, exposure to tobacco smoke (in adulthood and in utero), exposure to specific persistent (lead, organic pollutants) and nonpersistent (some phthalates, bisphenol A) environmental pollutants, and exposure to atmospheric pollutants. Even if each of these factors has a weak impact at the individual level, the large number of factors and the relatively high prevalence of exposure in the general population make it likely that at the population level, lifestyle and environmental factors put a high burden on male fecundity potential.