By Marie DeFreitas
A recent study has linked midlife obesity, not diet or inactivity, to long-term dementia risk.
The study was conducted in the UK by Dr. Sarah Floud, a senior epidemiologist at the Nuffield Department of Population Health at the University of Oxford. The study examined 1,136,846 women in the U.K over a period of nearly 20 years.
Studying the women’s weight, calorie intake and physical activity, they found that women who were obese at the beginning of the study were 21% more likely to develop dementia, compared to the women with a better BMI (body mass index.) The team used Cox regression models to calculate the associations between BMI and the diagnosis of dementia over the twenty year follow up period. They adjusted for the variables in the study, which included but were not limited to, age, height, education, and smoking status.
The average age of the women studied was 56, and they did not have dementia at the beginning of the study between the years 1996 and 2001. By the end of the study over 18,000 women had been diagnosed with dementia.
For the study, the Floud and her collegues considered a BMI of 20–24.9 as “desirable,” 25–29.9 as overweight, and 30 and over as obese. Women who exercised less than once a week were classified as inactive, while women who exercised at least once a week were seen as active.
As explained in the paper published by Floud and her colleagues, prior studies found an association with a low BMI and the likelihood of a dementia diagnosis with the following 5-10 years. Other shorter studies, ones that lasted a decade or less, also linked poor diet and lack of exercise with the diagnosis of dementia. However, that link weakened over time. By the fifteen year of the Floud’s study, neither of these factors were associated with dementia.
Floud went on to explain that “reverse causality”may be what’s at play in this study. Meaning that perhaps poor diet and lack of exercise may be consequences, rather than causes, of dementia. Floud and her colleagues believe this situation could be possible because dementia typically affects cognition a decade before the person formally receives a diagnosis.
Floud theorized that rather than these factors being risks, “[t]he short-term links between dementia, inactivity and low calorie intake are likely to be the earliest signs of the disease, before symptoms start to show.”
“During this preclinical stage, the condition can slowly but gradually affect behavior, impair mental and physical activity, reduce the intake of food and calories, and cause weight loss,” explained Medical News Today on the matter.
Ultimately, the study concluded that the women who had obesity at the beginning of the study were 21% more likely to develop dementia than women who had a lower BMI. About 2.2% of the women with obesity went on to develop dementia long term, as compared with the 1.7% of women with a healthier BMI.
Since the study was limited to women, these results may not apply to men. However, the results do present a step forward in the studies of the causes, factors and consequences of dementia.
The study was published in this week’s issue of Neurology on December 18.