SPENDING more time outdoors may be associated with healthier testosterone levels in adult men, according to new cross-sectional research using data from the US National Health and Nutrition Examination Survey (NHANES). The findings suggest that everyday environmental exposure could play a modest but independent role in male hormonal health.
Testosterone is influenced by a range of biological, behavioural, and environmental factors. However, modern lifestyles are increasingly sedentary, with many individuals spending the majority of their day indoors. While physical activity and vitamin D have been studied extensively in relation to testosterone, time spent outdoors (TSO) itself has received comparatively little attention.
To address this gap, investigators analysed data from 2,205 adult men who participated in NHANES between 2011 and 2014. Average daily TSO was measured in minutes, and morning serum total testosterone levels were recorded. Low testosterone was defined as a concentration below 300 ng/dL. The researchers used survey-weighted multivariable regression models to account for a wide range of potential confounders, including age, education, income, body mass index (BMI), physical activity (both self-reported and accelerometer-measured), diabetes status, vitamin D levels, and dietary habits.
The mean age of participants was 45.8 years, with an average testosterone level of 448.3 ng/dL and a mean daily outdoor exposure of approximately 144 minutes. Overall, 19.3% of men met the criteria for low testosterone.
Time Outdoors and Its Impact on Testosterone in Adult Men
After adjustment for confounding factors, greater TSO was significantly associated with higher serum testosterone levels. Each additional hour spent outdoors per day corresponded to an increase of 9.25 ng/dL in testosterone. Moreover, increased TSO was linked to a reduced likelihood of low testosterone, with a 14% decrease in odds per additional hour spent outside.
Consistent with previous research, increasing age, higher BMI, and the presence of diabetes were all positively associated with low testosterone, while higher levels of physical activity were inversely associated.
Testosterone and Modern Indoor Lifestyles
The authors note that this is the first study to demonstrate an independent association between outdoor time and testosterone levels, even after accounting for vitamin D and physical activity. While the cross-sectional design limits causal inference, the findings raise interesting questions about the potential hormonal impact of modern indoor lifestyles.
Further longitudinal and mechanistic studies are needed to determine whether increasing time outdoors could serve as a simple, low-cost strategy to support male reproductive and metabolic health.
Reference
Bhambhvani HP et al. Cross-sectional association of time spent outdoors with serum testosterone: results from the national health and nutrition examination survey. J Urol. 2026; 215(2):213–22.
