Longevity Briefs: 40% Of US Dementia Could Be Preventable With A Healthy Lifestyle

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: While dementia is rarely inherited, genetics do play an important role in determining the risk of developing dementia in later life. Perhaps the best known example is the APOE4 gene variant, the strongest risk factor for the development of Alzheimer’s disease. Dementia is currently incurable, but there may still be significant potential to reduce the incidence of dementia through lifestyle changes.

What did the researchers do: In this study published in JAMA Open, researchers analysed data from the US Behavioral Risk Factor Surveillance Survey. They looked at risk factors for dementia among 378 615 adult respondents, and attempted to calculate the proportion of Alzheimer’s disease cases and related dementias that were associated with modifiable lifestyle factors. Similar studies in the past had estimated this proportion at about 1 in 3, but these are outdated and many did not take the effects of sex and ethnicity into account.

Key takeaway(s) from this research: The authors estimate that about 41% of dementias in the US could be preventable through modification of 12 lifestyle factors. Obesity, high blood pressure, and lack of exercise were the most important risk factors, each contributing to about 20% of cases. However, this doesn’t account for the fact that these risk factors are interlinked – a person who doesn’t exercise is more likely to be obese and to have high blood pressure. When this confounder was accounted for, the three aforementioned risk factors still came out on top, each accounting for about 7% of cases.

Ethnicity appeared to affect the importance of many risk factors, which could be in part due to some conditions being more or less prevalent in certain ethnic groups, and also in part due to inequality and poor access to healthcare. Overall, modifiable risk factors appeared to play a greater role in the risk of dementia in men than in women, though this may be related to the fact that women live longer on average. Age remains the most important non-modifiable risk factor for Alzheimer’s disease, and so the proportion of dementia that is due to modifiable risk ls likely to be lower in women.

A previous report by the Lancet Commission estimated a similar proportion of dementia cases could be attributed to lifestyle factors. However this report, which focussed on worldwide dementia cases, placed hearing loss, educational level and smoking as the three most important risk factors. It’s therefore necessary to consider that the importance of different risk factors depends heavily on the population being studied.