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hTMA — Conscientiousness, Cortisol and Health Behaviour

Authors: Andrew Steptoea, Emma Easterlina, Clemens Kirschbaumb

Conscientious is associated with greater longevity and other favourable health outcomes, but the processes underlying these links are poorly understood. Health behaviours such as physical activity and avoidance of smoking and excessive alcohol consumption may contribute, but direct associations with neuroendocrine and inflammatory processes may also be relevant.

We tested the associations between conscientiousness and hair cortisol concentration in 2318 older men and women (mean age 66.2 years) from the English Longitudinal Study of Ageing. Conscientiousness was positively associated with physical activity and fruit and vegetable consumption, and negatively related to alcohol intake, sedentary behaviour, body mass index and depressive symptoms (all p < 0.001).

We found an inverse association between conscientiousness and hair cortisol concentration that was independent of age, sex, education and wealth (β=−0.053, p=0.012), and the relationship remained significant with additional adjustment for health behaviour and depressive symptoms (β=−0.048, p=0.025).

The observation that greater conscientiousness was correlated with lower hair cortisol indicates that this trait might impact central nervous regulation of hypothalamic-pituitary-adrenocortical function, with effects that are possibly advantageous for health.

Research Introduction

Conscientiousness is a trait characterized by self-discipline, dependability, and planfulness coupled with tendencies to follow socially prescribed norms and to be goal-directed. Conscientiousness appears to be an important determinant of longevity among older adults. For example, in an analysis of the Health and Retirement Study (HRS), conscientiousness predicted increased longevity after adjustment for age, gender, education, cognitive functioning, and reported health state. A large investigation aggregating seven cohort studies from Europe, the USA and Australia showed that low conscientiousness predicted increased mortality after age, sex, other personality traits and health behaviours were taken into account. Conscientiousness was also associated with reduced mortality in the Midlife in the United States (MIDUS) study, mediated in part by low alcohol consumption, less smoking, and lower waist circumference. Similar findings have been reported from the Whitehall II cohort study. Deary et al. (2008) reported that participants who were rated as dependable in childhood were more likely to be alive at age 65 years. Conscientiousness is also related to better health, including reduced incidence of diabetes, more positive self-rated health, and fewer depressive symptoms.

  1. One pathway relating conscientiousness to favourable health outcomes may be lifestyle choice. As noted above, associations between conscientiousness and mortality are mediated in part by health behaviour. Conscientiousness has been linked with reduced involvement in detrimental health behaviours such as smoking, heavy alcohol consumption, illegal substance use and risk-taking activity, while being positively correlated with physical activity, prudent diet, adherence to medication and other protective behaviours.
  2. A second possibility is that there are direct psychobiological processes linking conscientiousness with health outcomes. Conscientiousness is associated with reduced exposure to situations that elicit stress and with more effective coping with stressors. There is also evidence that greater conscientiousness is correlated with reduced inflammation, as indexed by C-reactive protein or interleukin (IL) 6 in theHRS, MIDUS, the National Longitudinal Study of Adolescent Health in the USA, and a study in Sardinia. Cortisol is a key biomarker relating psychosocial factors with health, since it is sensitive to stress and is implicated in a range of cardiometabolic, inflammatory, neural and endocrine disorders. However, evidence relating cortisol with conscientiousness is limited.

Hair cortisol concentration has emerged over recent years as an indicator of tonic cortisol output over several weeks, and is not subject to the acute variations related to momentary events and moods that influence salivary levels. It may therefore be particularly suitable for investigations of a relatively stable construct such as conscientiousness.

Accordingly, we analysed the association between conscientiousness and hair cortisol concentration in 2318 participants in the English Longitudinal Study of Ageing (ELSA), a nationally representative sample of men and women aged 50 and older living in England. We hypothesized that conscientiousness would be inversely related to hair cortisol concentration.

Cortisol in hair has also been associated with health behaviours such as smoking and physical activity, raising the possibility that relationships with conscientiousness are driven by differences in health behaviour. We therefore also tested with relationship between cortisol and health behaviours, and evaluated whether associations with conscientiousness remained robust after health behaviours had been taken into account. Depressive symptoms are also potential confounders, since they are associated with elevations of hair cortisol concentration, so were included in the analytic models.

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