Linking socioeconomic status and lifestyle to dementia risk

How socioeconomic status and healthy lifestyle choices combine to influence dementia risk, highlighting the impact of lifestyle on cognitive decline across SES groups.

Study: Associations of socioeconomic status and healthy lifestyle with incident dementia and cognitive decline: two prospective cohort studies. Image Credit: perfectlab / Shutterstock.com

A recent review published in The Lancet eClinical Medicine examines how socioeconomic status (SES) and healthy lifestyle factors interact to affect the risk of dementia.

SES and disease

SES is a complex of multiple factors, including income, education level, and occupation, that 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 proportion of this risk that can be attributed to an unhealthy lifestyle remains unclear. For example, one recent study reported that an unhealthy lifestyle is not the main contributor to the effects of socioeconomic inequality on the risk of cardiovascular disease and death.

Several behavioral risk factors exist for dementia, including smoking, drinking, and social engagement, are modifiable. 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 link between SES and dementia and how these factors collectively impact the risk of dementia and cognitive decline.

Data were obtained from the American Health and Retirement Study (HRS) conducted from 2008 to 2020, along with the English Longitudinal Study of Aging (ELSA) from 2004 to 2018. Study participants’ educational status, household income, and total wealth were used to determine their SES.

Healthy lifestyle scores were based on smoking history, low or moderate drinking, which was defined as none or one drink every day for women and none or up to two drinks each 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 participant age was 69.3 and 65.1 years, about 41% and 46% of whom were men, respectively.

About 26% and 24.7% of study participants from the HRS and ELSA cohorts were of high SES, with 24.2% and 29.7% of low SES, respectively. Most high SES individuals were men, married, employed, and wealthier, with more education, less likely to be depressed or have medical conditions.

Fewer individuals with high SES had a high body mass index (BMI), blood pressure, or blood sugar. 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 comprised about 10.4% and 2.7% of the dementia risk in the HRS and ELSA medium SES subgroups, respectively, as compared to 18.4% and 1.7% in the low SES groups, respectively. Thus, an unhealthy lifestyle mediates less than 20% of the total risk for dementia caused by low SES.

Men with a low SES were at a 3.38-fold risk as compared to low SES women who were 2.45-fold more likely to develop dementia. This risk was higher in midlife than late life at 5.26 and 2.48 in the HRS, respectively, and 2.23 and 1.18 in the ELSA cohort, respectively.

Lifestyle-SES combination

A healthy lifestyle reduced the risk of dementia by about 33% among those with medium 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 redued risk of new-onset dementia by 6-16%, depending on the SES.

With a low SES, an unhealthy lifestyle increased the risk of dementia onset. As compared to those with high SES and a healthy lifestyle, the risk of developing dementia was 4.27-fold greater in the HRS as compared to a 2.02-fold increased risk in the ELSA cohort.

Despite a healthy lifestyle, low SES increased the risk of dementia to 2.78- and 1.86-fold respectively, as compared the reference group. Similarly high increases in risk were observed with medium SES and a poor lifestyle.

The rate of cognitive decline increased in association with this combination of factors.

Individual lifestyle factors

In the HRS cohort, lower education, household income, and household wealth increased the risk of dementia by 4.5%, 7.8%, and 19.8%, respectively, when comparing the lowest and highest SES levels. 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 for dementia among those with low and high SES, whereas differences in physical activity mediated 24.3% of the risk in the ELSA cohort.

Harmful drinking was responsible for a large proportion of the risk for dementia, mostly in the HRS cohort.

Conclusions

Unhealthy lifestyle factors were responsible for a small part of the increased risk for dementia onset 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 levels of SES, a healthier lifestyle was associated with a lower risk of dementia.

These findings support the important role of healthy lifestyles in reducing dementia burden.”

However, dementia risk is markedly higher with a low SES. Thus, active interventions are essential to reduce socioeconomic inequality by targeting the social determinants of health, helping to maintain brain health.