We are often reminded of the importance of maintaining a healthy bodyweight for our overall health, so it is no surprise that not being excessively overweight is a protective factor also with regards to dementia.
This was proven by a longitudinal study of over 30 years, looking at how bodyweight, BMI, waist circumference, and waist-to-hip ratio (WHR), were related to dementia in 1462 women.
At the end of this very detailed study, researchers were able to observe a twofold increase in dementia risk after 32 years with a high midlife measure of central adiposity, defined as more than 0.80 in WHR. Noticeably, this number is also the one associated with higher mortality overall.
The researchers are quite confident that their results are correct, and amongst the strength of their study they list 32 years of continuous follow-up to high age, a wide and representative sample, and a series of comprehensive neuropsychiatric examinations. However, they also recognize and address limits of their study, such as being often complicated to discern between Alzheimer’s and Vascular dementia, although the researchers were admittedly very strict with their criteria for considering some participant as having Alzheimer’s disease and were aided in this by a team of expert psychiatrists. Also, the sample type proved problematic, since while it was representative of the population, it was also quite homogeneous, consisting of Swedish women from one city, thus the results may not necessarily be replicable in other settings.
Nevertheless, the scientists were able to say with a certain degree of certainty that the prevention of overweight and obesity during midlife might be important for the prevention of dementia.
Gustafson, D.R., et al., (2009), Adiposity indicators and dementia over 32 years in Sweden, in “Neurology”, 73(19), pp. 1159 – 1566.