Intensity-dependent associations of physical activity and cardiorespiratory fitness with hair cortisol concentrations in the context of lifetime air pollution exposure

Abstract

Hair cortisol concentration (HCC) is used as a biomarker of chronic stress. While evidence linking HCC to physical activity is mixed, associations with cardiorespiratory fitness remain unexplored, and the contribution of long-term ambient air pollution is unclear. This study examined associations of HCC with objectively and subjectively assessed moderate and vigorous physical activity, cardiorespiratory fitness, and estimated lifetime ambient air pollution exposure. Data were obtained from a subsample of adults (N = 133; 87% women) participating in the Healthy Aging in an Industrial Environment-Programme 4 study (4HAIE). HCC was quantified from 3-cm hair segments using liquid chromatography-tandem mass spectrometry, reflecting cortisol exposure over approximately 3 months. Physical activity was assessed using the Leisure-Time Exercise Questionnaire (LTEQ) and 14-day Fitbit monitoring, and cardiorespiratory fitness by peak oxygen uptake (VO2peak). Lifetime exposure to particulate matter (PM2.5 and PM10) and nitrogen dioxide (NO2) was estimated from residential histories and historical air pollution models. Associations were examined using multiple linear regression and hierarchical models. Vigorous physical activity was positively associated with HCC in both self-reported (LTEQ: B = 0.010, p = 0.042) and objectively measured data (Fitbit: B = 0.006, p = 0.044). VO2peak was initially associated with higher HCC (B = 0.019, p = 0.041), but this association was attenuated after inclusion of vigorous physical activity. Neither moderate physical activity nor lifetime air pollution exposure was significantly associated with HCC. These findings suggest that vigorous physical activity may contribute to higher HCC, highlighting the importance of considering physical activity intensity when interpreting HCC as a biomarker of chronic stress.

The authors' abstract, as published at the source. Stress, 2026 · DOI ↗