A newly published study in the journal Nature Communications identifies several lifestyle factors that may accelerate cognitive decline.

Study: Healthy lifestyle and cognitive decline in middle-aged and older adults residing in 14 European countries. Image Credit: Josep Suria / Shutterstock.com

Lifestyle habits that may increase dementia risk

Many behavioral and lifestyle factors are potential determinants of the pace of cognitive aging and risk of dementia, some of which include exercise, smoking, drinking, and sleep patterns. These factors may act independently or together to affect cognitive aging trajectories.

Typically, research studying the link between cognitive decline and lifestyle patterns primarily utilizes healthy lifestyle indices, which do not consider individual behaviors and assume an equal contribution of all healthy behaviors to cognitive function. As a result, these studies cannot be relied upon solely when designing interventions.

Thus, additional studies are needed to better understand how specific behavioral factors combine to affect cognitive decline. Prodromal dementia symptoms can influence behavioral patterns many years before clinical diagnosis, which further emphasizes the importance of these studies. Identifying risk factors for cognitive decline in individuals not yet experiencing disease-related symptoms is also crucial.

About the study

The current study used up to 15 years of longitudinal data on 32,000 adults to elucidate the relationship between lifestyle factors and cognitive decline. Data were obtained from 14 European countries on individuals between 50 and 104 years of age who did not have dementia or cognitive impairment.

The associations between 16 lifestyle factors and 10-year cognitive decline were studied with respect to episodic memory and verbal fluency. The lifestyle factors included alcohol consumption, smoking, social contact habits, and physical activity.

Study findings

Slower cognitive decline in both memory and fluency was associated with no smoking and none or moderate alcohol consumption. As compared to individuals who smoked for over 10 years, non-smokers had memory scores that declined 0.08 standard deviations (SD). Likewise, no-to-moderate alcohol consumption was associated with memory scores that declined 0.04 SD less than heavy alcohol drinkers.

In addition to smoking, weekly social contact or less was associated with more rapidly declining memory scores, regardless of the individual’s alcohol consumption or physical activity habits. Individuals who reported both weekly social contact and smoking exhibited faster memory decline as compared to the reference lifestyle.

These results are in agreement with previous studies reporting a correlation between low-to-moderate alcohol consumption, smoking, and better cognitive outcomes. The adverse effects of smoking on cognition could be attributed to its negative impact on cardiovascular function.

Light-to-moderate alcohol consumption has also been related to muted activity in regions of the brain associated with stress. Sensitivity analyses excluding alcohol abstainers revealed that the inclusion of individuals who never consumed alcohol did not significantly influence the results.

Physical activity protects against aging-related neuronal loss and fortifies mechanisms against neurodegeneration, thereby protecting individuals from dementia and cognitive decline.

Social engagement and activity could also provide neuroprotection by mediating the association between cognitive function and brain atrophy. Social bonding could also mediate the association between cognitive function and perceived stress.

Conclusions

Substantial evidence supports the hypothesis that smoking, alcohol consumption, social contact, and physical activity are associated with cognitive health, regardless of when these lifestyle factors are studied independently or combined into a healthy lifestyle index.

The main strength of the current study is its large population and long follow-up period. This aided the evaluation of 16 lifestyle profiles with sufficient power to identify important differences in cognitive decline.

Additionally, the risk of reverse causality was mitigated by focusing on cognitive decline rather than cross-sectional cognitive performance. Cognitive scores were also standardized to each country, which reduced cross-country differences.

Nevertheless, all behaviors were self-reported, which could increase the risk of recall bias. Due to the lack of alcohol variables, the behavior changes could not be accounted for during the follow-up period.

The lack of data also precluded the consideration of other factors, such as medication use, which could confound the association between cognitive function and lifestyle. Furthermore, sleep and diet could not be included in the analysis, although both factors may impact cognitive decline.

Participants with less healthy lifestyles could have dropped out of the study during the follow-up period; therefore, differential attrition could have influenced the results. Importantly, the current study considered data only from European countries, thus limiting the generalizability of the findings and necessitating future studies that include more diverse populations to confirm these results.