How socioeconomic status and healthy lifestyle choices jointly influence dementia risk, highlighting the impact of lifestyle on cognitive decline across all SES groups.
Study: Associations of socioeconomic status and healthy lifestyle with incident dementia and cognitive decline: two prospective cohort studies. Image credits: perfectlab / Shutterstock.com
A recent review published in The Lancet eClinical Medicine examines how socioeconomic status (SES) and healthy lifestyle factors interact to influence dementia risk.
SES and disease
SES is a complex of multiple factors, including income, education level and occupation, which collectively refer to an individual’s social and economic position within society.
The role of socioeconomic inequality in many medical conditions, including dementia, is well established; however, the portion of this risk that can be attributed to an unhealthy lifestyle remains unclear. For example, a recent study shows that an unhealthy lifestyle is not the main contributor to the effects of socio-economic inequality on the risk of cardiovascular disease and death.
Several behavioral risk factors for dementia exist, including smoking, drinking and social involvement, which can be modified. Therefore, it is crucial to determine the weighted impact of an unhealthy lifestyle on the development of dementia.
About the study
The aim of the current study was to understand whether overall lifestyle contributes to the association between SES and dementia and how these factors jointly influence the risk of dementia and cognitive decline.
Data were obtained from the American Health and Retirement Study (HRS), conducted from 2008 to 2020, together with the English Longitudinal Study of Aging (ELSA) from 2004 to 2018. The educational status, household income, and total wealth of participants in the study were used to determine their SES.
Healthy lifestyle scores were based on history of smoking, little or moderate drinking, defined as no or one drink per day for women and no or up to two drinks for men, regular vigorous physical activity and social activity.
Risk variation by SES
A total of 12,437 and 6,565 participants from the HRS and ELSA studies, respectively, were included in the study. The mean age of participants was 69.3 and 65.1 years, of whom approximately 41% and 46% were men, respectively.
Approximately 26% and 24.7% of study participants from the HRS and ELSA cohorts had high SES, while 24.2% and 29.7% had low SES, respectively. Most people with high SES were men, married, working and wealthier, with higher education, and less likely to have depression or medical conditions.
Fewer individuals with high SES had high body mass index (BMI), blood pressure, or blood sugar levels. These individuals were also more likely to report healthy levels of smoking and drinking, while also participating in adequate physical activity and social contact.
Risk variation by lifestyle
The least healthy lifestyle accounted for approximately 10.4% and 2.7% of dementia risk in the HRS and ELSA subgroups with average SES, respectively, compared to 18.4% and 1.7%, respectively, in the low SES groups. An unhealthy lifestyle therefore mediates less than 20% of the total risk of dementia caused by low SES.
Men with low SES were at 3.38 times greater risk than women with low SES, who were 2.45 times more likely to develop dementia. This risk was higher in middle age than in later life, with 5.26 and 2.48 in the HRS, and 2.23 and 1.18 in the ELSA cohort, respectively.
Lifestyle-SES combination
A healthy lifestyle reduced the risk of dementia by approximately 33% among those of average and low SES in the HRS cohort; however, this effect was not observed in the ELSA cohort. Each unit increase in the total healthy lifestyle score was associated with a reduced risk of early-onset dementia by 6-16%, depending on SES.
With a low SES, an unhealthy lifestyle increases the risk of developing dementia. Compared to those with high SES and healthy lifestyles, the risk of developing dementia was 4.27 times greater in the HRS compared to a 2.02 times increased risk in the ELSA cohort.
Despite a healthy lifestyle, low SES increased the risk of dementia up to 2.78 and 1.86 times, respectively, compared to the reference group. Similar high risk increases were observed with average SES and poor lifestyle.
The rate of cognitive decline increased in association with this combination of factors.
Individual lifestyle factors
In the HRS cohort, lower education level, lower household income, and lower household wealth increased the risk of dementia by 4.5%, 7.8%, and 19.8%, respectively, when the lowest and highest SES levels were compared . In the ELSA study, lower household wealth increased the risk of dementia by 62%.
Smoking and social interactions mediated less than 1% of the increased risk of dementia among people with low and high SES, while differences in physical activity mediated 24.3% of the risk in the ELSA cohort.
Harmful drinking was responsible for much of the risk of dementia, especially in the HRS cohort.
Conclusions
Unhealthy lifestyle factors were responsible for a small proportion of the increased risk of developing dementia in both English and American older adults. Approximately 1.7% to 18.4% of this increased risk was mediated by lifestyle factors in lower SES adults. Nevertheless, at all SES levels, a healthier lifestyle was associated with a lower risk of dementia.
These findings support the important role of a healthy lifestyle in reducing the burden of dementia.”
However, the risk of dementia is significantly higher with low SES. Active interventions are therefore essential to reduce socio-economic inequality by targeting the social determinants of health, thus helping to maintain brain health.
Magazine reference:
- Wang, K., Fang, Y., Zheng, R., et al. (2024). Associations of socioeconomic status and healthy lifestyle with incident dementia and cognitive decline: two prospective cohort studies. The Lancet eClinical Medicine. doi:10.1016/j.eclinm.2024.102831.