Abstrak: Reduction of dietary sodium intake has been identified as a priority to reduce the worldwide burden of hypertension and cardiovascular disease. Dietary sodium intake is most precisely ascertained by using timed urine collection. Casual urine sodium measurements are relatively easy to perform, but their relationship to timed urine sodium measurements is unclear. In this issue of the Journal, Brown et al. (Am J Epidemiol. 2013;177(11):1180-1192) report the development and validation of equations to estimate 24-hour urine sodium excretion from casual urine samples. Their study included a large number of participants on 2 continents, a well-collected gold standard, separate discovery and validation samples, and relevant covariates. The resulting equations represent the best available methods to estimate dietary sodium intake from casual urine samples. However, the study is limited by evidence of a suboptimal model fit, restriction to people 20-59 years of age in North America and Europe, and exclusion and adjustment that further limit external validity. In addition, individual-level correlations of estimated and measured 24-hour urine sodium excretion were modest. Properly applied, the results will facilitate tracking of dietary sodium intake within populations over time and identification of communities for which dietary sodium restriction is most likely to be beneficial. Further work is needed to extend estimation to additional populations and improve individual-level assessment.

Abstrak: 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.