Socio-demographic and psychosocial predictors of salivary cortisol from older male participants in the Speedwell prospective cohort study

Introduction Associations between measures of socio-economic position and cortisol remain controversial. We examined the association between social class and cortisol reactivity in an aging male population. Methods The Speedwell cohort study recruited 2348 men aged 45–59 years from primary care between 1979 and 1982 (phase I) where occupational social class was used to classify socioeconomic position. Men were seen on four more occasions, the last being between 1997 and 1999 (phase 5) when salivary samples were obtained capturing cortisol reactivity to stressors (cognitive test and venepuncture) and circadian variations (awakening and night-time cortisol levels, circadian slope and area under curve) at morning and afternoon clinic sessions. Longitudinal association between social class at phase 3 and log-transformed salivary cortisol measures at phase 5 was assessed using multivariable linear regression adjusted for variables associated with sampling time and age as a potential confounder, stratified by time of clinic session. We also explored possible mediation by psychosocial factors (e.g. work dislike) and health-related factors (e.g. waist-to-hip ratio and high-density lipoprotein cholesterol). Results From 1768 living men, 1003 men (57%) attended a clinic at phase five, 854 participants (85% of attendees) returned home cortisol samples (mean age 71.7 years). We found little evidence of association between social class and baseline cortisol (i.e. prior to stress), cortisol response to stressors, and cortisol diurnal variation. However, we found lower social class was associated with higher and delayed post-stress recovery cortisol for participants that visited the clinic in the morning (adjusted β coefficient for manual versus non-manual 0.25 ng/ml; 95% CI: 0.06–0.48; P = 0.008). This association did not appear to be mediated by any of the measured psychosocial or health-related factors. Conclusion Our data did not show an overall association between social class and cortisol variability either diurnal or in response to a stressor. Lower social class was associated with a slower time to recover from exposure to stress in the morning, thereby increasing overall cortisol exposure. These findings provide some evidence for a mechanism that may contribute to the association between lower social class and a higher risk of adverse health outcomes.