The association between stress and multiple long-term conditions: A cohort study

Background: Stress is an important predictor of long-term conditions. We examine whether hair cortisol (a biomarker of stress) is associated with incidence and accumulation of multiple long-term conditions (MLTC). Methods: We included data from 4295 individuals aged >= 50 years within the English Longitudinal Study of Ageing dataset with data on hair cortisol, sociodemographic and health behaviour variables. Cox proportional hazards models were used to quantify the association between hair cortisol at baseline and accumulation of MLTC between 2012/2013 and 2018/2019, both for individuals with and without MLTC at baseline. Results: Our cohort included 1458 (34.0%) individuals who accumulated MLTC between 2012/2013 and 2018/ 2019. The proportion of individuals with zero, 1, and >= 2 conditions at baseline who accumulated MLTC were 12.0% (n = 127), 40.4% (n = 520), and 41.7% (n = 811), respectively. Higher cortisol levels were associated with higher risk of accumulation of MLTC in both unadjusted [HR:1.15(1.05-1.25)] and models adjusted for sociodemographic and health behaviours [HR:1.12(1.02-1.22)]. For individuals without MLTC at baseline, higher cortisol levels were significantly associated with higher risk of developing MLTC in unadjusted [HR: 1.20 (1.05-1.36)] and adjusted models [HR: 1.16(1.02-1.32)]. Conclusion: The study provides the first evidence of the role of stress in the development and accumulation of MLTC. This modifiable risk factor could be targeted to reduce the risk of MLTC. However, further work is needed to better understand the mechanisms and pathways that link stress and accumulation of MLTC.