A new study on over 1 milion women in the UK has found that women who are obese during their 50’s are at a higher risk than women with healthier physiques. They however found no correlation between calorie intake and physical activity, and the onset of dementia.
Previously, studies have found a link between a low body mass index (BMI) and the likelihood of being diagnosed with dementia within 5-10 years. Others have suggested a link between poor diet and a lack of exercise with the onset of dementia. Yet, new findings from a study at Oxford University, UK now suggest that these results may indeed stem from a reverse causality, meaning that rather than triggering the disease, they are in fact consequences.
For the study, researchers examined data from 1,136,864 women in the UK at an average age of 56 years. Free from dementia at the beginning of the study, between 1996 and 2001, the health of these women was tracked until 2017 using records from the country’s National Health Service.
During their research, a BMI of 20-24.9 was considered “desirable”, 25-29.9 as overweight, and 30 and over as obese. Women who exercised less than once per week were considered “inactive: whereas those who exercised at least once per week were seen as active.
Using Cox regression models, the researchers calculated the relationships between BMI and the incidence of dementia over the follow-up period, adjusting for variables such as age, cigarette intake, education and residential area.
During the period analyzed, 11% of the women, or 18,695 of the original cohort, received a dementia diagnosis. In total, the researchers found that women who were obese at the start of the study period were 21% more likely to receive a dementia diagnosis than those with a BMI’s under 24.9. Moreover, they found that 2.2% of obese women developed dementia in the long term, whereas the same could be said about just 1.7% of those with healthier BMI’s.
Although low calorie intake and less physical activity seemed to be linked to a higher risk for dementia during the study’s first decade, the link seemed to lose strength later on. Lead author of the study, Sarah Floud, said, “The short-term links between dementia, inactivity, and low calorie intake are likely to be the result of the earliest signs of the disease, before symptoms start to show.”
This may be the case as cognitive deficits usually begin around a decade before a formal diagnosis of dementia. These cognitive deficits usually appear gradually, but may impair both mental and physical activity, as well as reduce food intake and calories, eventually leading to weight loss.
Floud continued, “On the other hand, obesity in midlife was linked with dementia 15 or more years later. Obesity is a well-established risk factor for cerebrovascular disease. Cerebrovascular disease contributes to dementia later in life."