In a recent study published in the journal nature human behaviorThe researchers evaluated the causal effects of mental well-being on genetically independent aging phenotypes (aging GIPs).
Human life expectancy has increased over time; however, aging populations present challenges for individuals and society. Mental health is related to lifestyle behaviors and morbidity. Studies have linked mental health to physical health and increased survival. In addition, socioeconomic status (SES) is associated with aging and mental health. However, a causal relationship between healthy aging and mental health has not yet been established.
Study: Mendelian randomization evidence for a causal effect of mental health on healthy aging. Image credit: Darren Baker / Shutterstock
About the study
In the current study, the researchers assessed the effects of mental health on aging symptoms. This Mendelian randomization (MR) study evaluated the causal relationships between aging symptoms and mental health symptoms and examined candidate mediators in the relationship between GIP and the health spectrum of aging. In addition, the team also explored whether the causal effects were SES-independent.
Summary-level genome-wide association study (GWAS) data were obtained from people of European descent. Exposures included the well-being spectrum, life satisfaction, neuroticism, depressive symptoms and positive affect. Covariates were three SES indicators – education, occupation and income. In total, 106 candidate mediators were identified for screening; the mediators included 23 lifestyle factors, 20 physical function traits, 53 diseases and 10 behaviors and performance.
Mediators were selected based on a set of criteria: the mediator must have a causal relationship with old-age GIP and a direct causal effect independent of the well-being spectrum; the well-being spectrum must have a causal relationship with the mediator (and not vice versa); the relationship of the mediator with old-age GIP and the relationship of the well-being spectrum with the mediator must be in the same direction.
Outcomes included old-age GIP and its components (self-rated health, resilience, longevity, health span and parental lifespan). Linkage disequilibrium score regression was performed to examine genetic correlations between mental health symptoms, old-age symptoms and SES indicators. Univariable MR (UVMR) analysis assessed the causal effects of mediators and mental health symptoms on old-age symptoms.
UVMR and multivariable MR (MVMR) analyses were conducted to examine the causal effects of SES indicators on mental health symptoms. MVMR analysis adjusted for SES indicators examined the direct effect of the well-being spectrum on aging symptoms. Two-step MR analysis tested the mediating effect between the well-being spectrum and the GIP of aging.
Findings
Genetic correlations were observed between all mental health traits and old-age GIP and its components except longevity. Well-being spectrum was associated with an increase in old-age GIP. Consistently, well-being spectrum showed positive causal relationships with resilience, health span, parental life span and self-rated health.
Positive affect and life satisfaction were positively associated with these geriatric traits, whereas depressive symptoms and neuroticism were inversely associated. SES indicators and well-being traits were also correlated. Higher income, education and occupation were causally associated with better mental well-being. The well-being spectrum was independently associated with higher geriatric GIP, adjusted for SES indicators.
Of the 106 candidate mediators, 33 met the screening criteria and were included. Unhealthy lifestyle factors, physical function and behavior, and performance were associated with lower aging GIP. Later age of smoking initiation and higher cheese intake, appendicular lean mass (ALM), cognitive performance, high-density lipoprotein cholesterol (HDL-C), and fresh fruit intake were associated with higher aging GIP.
Heart attack, hypertension, stroke and coronary heart disease had the largest effect sizes on geriatric GIP. Antihypertensive medication, age at smoking initiation and television viewing time individually mediated at least 7% of the effect of the health spectrum on geriatric GIP. Non-steroidal anti-inflammatory medications, waist-to-hip ratio, fresh fruit intake, ALM, HDL-C, triglycerides and age at menstruation individually mediated up to 4.81% of the total effect.
conclusion
In summary, the study demonstrated causal effects of mental health on aging symptoms independent of SES. Better mental health was associated with better aging GIP. The causal effect was partially explained by 33 mediators, including lifestyle, physical function, disease, and behavior and performance. Overall, the results highlight the need to prioritize mental health for healthy aging.