Healthy mental health improved physical well-being in old age
A large analysis using Mendelian randomisation showed that better mental health scores were causally associated with better physical health in older adults. High life satisfaction and positive emotions, together with low rates of neurosis and depression, led to a healthier ageing phenotype - such individuals had higher resilience and longer life expectancy. Notably, one mediator of this association was high cheese consumption. The analysis is published in Nature Human Behaviour.
Human life expectancy has increased significantly in recent decades, and the resulting ageing population poses public health challenges. Therefore, more and more energy is being devoted to healthy ageing, in which quality of life does not decline with increasing life expectancy. Mental health, which includes emotional, psychological, and social well-being, correlates with a variety of lifestyles and illnesses and underlies healthy aging.
Previous national surveys and prospective cohort studies have linked better mental health, defined by subjective well-being, optimism, or self-rated mental health, with high physical health. However, due to inherent limitations of observational studies, such as erroneous bias and reverse causality, the true causal relationship between mental wellbeing and healthy ageing has not yet been established.
To clarify this issue, a team of scientists led by Tian-Ge Wang from Shanghai Jiao Tong University conducted a study using Mendelian randomisation, which pooled datasets from a full genome-wide association search of several cohorts - ranging from 80852 to 2370390 observations. Mental health was assessed using four attributes of mental wellbeing - life satisfaction, positive emotions, neuroticism and depressive symptoms. Researchers defined the components of healthy physical aging as resilience, self-rated health, parental longevity, and longevity.
Regression analysis of the relationship between the indicators revealed a genetic correlation of all mental well-being traits with the components of healthy aging (from p = 8.99 ×10-105 to p = 2.74 ×10-5). Life satisfaction and positive affect had a positive relationship, whereas neuroticism and depressive symptoms had an inverse relationship with the healthy aging phenotype. All Mendelian randomisation results for each individual physical health component were confirmed by at least one sensitivity analysis. In addition, further analyses showed genetic correlations between the three socioeconomic indicators and all mental well-being traits (from p = 4.29 × 10-28 to p = 5.85 × 10-10). Higher genetically determined household income, educational attainment, and occupational attainment were causally associated with better mental well-being.
Adjusting for each socioeconomic indicator did not reduce the statistical significance of the causal relationships found between the components of mental health and the components of healthy aging. Following the mediator selection process, 33 of 106 candidates met all selection criteria and were selected as mediators of the association between mental wellbeing and healthy ageing: five lifestyle factors, four types of behaviour and activity, five physical functions and 19 diseases. For example, watching TV and increasing the number of white blood cells in the blood had a negative effect on the phenotype of healthy ageing mediated by mental wellbeing. And increased consumption of cheese, fresh fruit, cognitive ability, and high-density lipoprotein levels were associated with higher scores on the components of healthy aging.
The disease that had the greatest impact on healthy aging was heart failure (p = 3.32 × 10-13), followed by hypertension (p = 7.66 × 10-13), stroke (p = 2.88 × 10-4), and coronary heart disease (p = 1.24 × 10-12). Among lifestyle factors, behaviour and performance, and physical function, the most prominent were hypotensive medication (mean proportion 9.54 percent), TV viewing time (7.39 percent) and age of smoking initiation (7.16 percent).
This study sheds light on the causal relationship of mental well-being with the aging phenotype regardless of socioeconomic status. The results also describe the multifaceted mediating pathways of this relationship. Thus, this work provides an evidence base for the development of preventive public health interventions to improve the quality of life of older adults.