A healthy lifestyle is typically associated with a reduced risk of cognitive decline in older adults. However, among lifestyle habits, researchers have now identified the key factor that has the most effect on the cognitive health of the elderly.

According to the latest study led by UCL researchers, which involved evaluating around 32,000 adults over the age of 50 from 14 European countries, smoking emerged as the most important lifestyle factor that decides the rate of cognitive decline.

For the study, the researchers considered the rate of cognitive decline concerning four health- behaviors: smoking, alcohol consumption, physical activity, and social contact. The cognitive function of the participants was measured using memory and verbal fluency tests.

Participants were categorized by their lifestyles, taking into account whether they smoked, engaged in moderate or vigorous exercise at least once a week, interacted with friends and family weekly, and consumed alcohol within specified limits (up to two drinks per day for men or one drink per day for women).

The researchers noted that cognitive decline was significantly faster in individuals who smoked, with their cognitive scores dropping up to 85% more over 10 years compared to non-smokers. Meanwhile, cognitive decline was generally similar across all non-smoking lifestyles.

However, smokers who had other three healthy habits such as regular exercise drinking alcohol in moderation, and socializing regularly had a rate of cognitive decline similar to non-smokers.

The researchers caution that factors such as age, gender, country, education, wealth, and chronic conditions must have affected the study findings.

"Our study is observational so cannot definitively establish cause and effect, but it suggests smoking might be a particularly important factor influencing the rate of cognitive aging. Previous evidence suggests individuals who engage in more healthy behaviors have slower cognitive decline; however, it was unclear whether all behaviors contributed equally to cognitive decline, or if there were specific behaviors driving these results. Our findings suggest that among the healthy behaviors we examined, not smoking may be among the most important in terms of maintaining cognitive function," Dr. Mikaela Bloomberg, Lead Author, UCL Behavioural Science & Health, said in a news release.

"For people who aren't able to stop smoking, our results suggest that engaging in other healthy behaviors such as regular exercise, moderate alcohol consumption, and being socially active may help offset adverse cognitive effects associated with smoking," Dr. Bloomberg added.