Cross-Sectional Association of Time Spent Outdoors with Serum Testosterone: Results from NHANES

Testosterone levels are influenced by behavioral and environmental factors. As modern lifestyles have become increasingly sedentary with less time spent outdoors, understanding how daily outdoor exposure relates to serum testosterone may offer insight into the hormonal effects of contemporary behavior patterns. We evaluated the correlation between daily time spent outdoors (TSO) and serum testosterone. We identified adult men from the National Health and Nutrition Examination Survey (NHANES) database from 2011-2014. TSO was measured in average minutes per day (MPD). Low testosterone was defined as serum morning total testosterone < 300 ng/dL. Survey-weighted multivariable logistic and linear regression models were used to identify factors correlated with low testosterone and serum testosterone, respectively, while correcting for age, education, household income, BMI, physical activity (both self-reported and accelerometer-determined), diabetes, vitamin D concentration, and dietary habits. 2,205 men were included. Mean age, testosterone, and MPD TSO were 45.8 years, 448.34 ng/dL, and 144.3 minutes, respectively. 19.3% of men had low testosterone. TSO was significantly associated with both serum testosterone (β=9.25 per 1 hour outside daily, p=0.007) and decreased odds of low testosterone (OR=0.86 per 1 hour outside daily, 95% CI 0.76-0.97, p=0.01) in multivariate analysis. Increasing age, BMI, and diabetes were positively correlated with low testosterone, while increasing physical activity was inversely correlated with low testosterone (p≤0.01 for all). This is the first report to describe a correlation between increased outdoor time and lower prevalence of low testosterone, independent of age, education, household income, BMI, physical activity, diabetes, vitamin D concentration, and dietary habits.