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22nd April 2022
People who adopt a healthy lifestyle are not only more likely to live longer but also have a reduced risk of developing Alzheimer’s disease compared with those who lead a less healthy lifestyle. This was the finding of an analysis of data from the Chicago Health and Ageing Project (CHAP) by a team from the Rush Institute for Healthy Aging, Rush University Medical Center, Chicago, USA.
Alzheimer’s disease is the most common form of dementia with a high level of inheritability which is thought to be between 60% and 80%. Nevertheless, while genetic factors are associated with a higher risk of developing AD, the extent to which lifestyle modification can off-set this risk is unclear, although some data shows that a favourable lifestyle was associated with a lower dementia risk even among participants with high genetic risk. In fact, evidence suggests that when compared to those with no to only one healthy lifestyle factor, the risk of Alzheimer dementia was 60% lower in those with 4 to 5 healthy lifestyle factors. Since the greatest risk factor for Alzheimer’s disease is advanced age, for the present study, the US team wanted to explore the impact of a healthy lifestyle on both life expectancy lived with and without AD.
The researchers turned to the CHAP, which is a prospective study designed to assess risk factors for AD. To explore the impact of a healthy lifestyle, they created a scoring system which included five recognised and modifiable lifestyle factors: diet, cognitive activities (e.g., reading, doing crosswords, puzzles etc), physical activity, smoking and alcohol consumption. For each of these five factors, researchers assigned individuals a score of 1 (if they met the threshold for a healthy or low risk score) or 0 (where they did not meet the criteria). An individual’s score was then summed, ranging from 0 to 5. The main outcome of interest was life expectancy with and without AD in both sexes.
Healthy lifestyle and life expectancy
A total of 2449 individuals with a mean age of 76.2 years were included in the analysis and the mean lifestyle score was 2.3.
During 13,047 person years of follow-up, 20.8% of participants developed incident AD. Among women with between 4 and 5 healthy lifestyle factors, the risk of AD compared to those with 0 or 1 factors was significantly reduced (hazard ratio, HR = 0.44, 95% CI 0.32 – 0.59). A similar reduction was also evident for me (HR = 0.30, 95% CI 0.19 – 0.47).
The benefits of a healthy lifestyle also led to a reduced mortality risk compared to those with 0 to 1 factors in both women (HR = 0.56, 95% CI 0.49 – 0.65) and men (HR = 0.47, 95% CI 0.39 – 0.57).
The authors calculated that the life expectancy of women aged 65 but without Alzheimer’s dementia and four or five healthy factors was 21.5 years compared to 17 years for those with either 0 or 1 healthy factors. Similar benefits were also seen for men.
The impact of a high healthy lifestyle score also affected the number of years spent with AD. For example, of the total life expectancy of women aged 65, those with four or five healthy factors spent 2.6 years (10.8%) with Alzheimer’s dementia. In contrast, women with 0 or one healthy factor, spent 4.1 years (19.3%) with the disease. Again, similar benefits were seen for men.
The authors concluded that a healthy lifestyle not only increased life expectancy but it was likely to reduce the proportion of remaining years lived with AD.
Dhana K et al. Healthy lifestyle and life expectancy with and without Alzheimer’s dementia: population based cohort study BMJ 2022