If this is your BMI, you are more at risk for dementia

You probably don’t need a scientific study to tell you that obesity is an unhealthy condition from a physical health perspective. Obese individuals are at a greater risk of numerous physical health problems, such as diabetes, heart disease, and an overall shorter life expectancy. 

Now, however, a new study from University College London has concluded that obesity can also raise one’s risk of developing dementia – up to 15 years later. According to researchers’ calculations, being obese in late adulthood raises an individual’s odds of developing dementia by a significant 31% in comparison to people with a “normal” BMI. Moreover, obese women appear to be at a higher risk of dementia than obese men.

Dementia, of course, is a blanket medical term used to describe any number of abnormal brain changes that interfere with one’s ability to think, recall memories, communicate, or problem-solve. The most well-known form of dementia is probably Alzheimer’s. 

“These findings provide new evidence that obesity may have important implications in terms of dementia risk,” comments senior study author Dr. Dorina Cadar, of the UCL Institute of Epidemiology & Health Care, in a release.

“Both BMI and waist circumference status should be monitored to avoid metabolic dysregulations. Hence, reducing weight to optimal levels is recommended by adopting healthy and balanced patterns of eating, such as the Mediterranean diet, appropriate physical exercise, and reduced alcohol consumption throughout the course of the entire adult life span,” she continues.

For this research, the team at UCL gathered data on 6,582 older adults (aged 50 or older). That information was originally collected as a nationally representative sample of the English population for an earlier research project called the English Longitudinal Study of Aging. For each studied adult, three distinct sources were used to determine dementia status/risk level: hospital statistics, doctor diagnoses, and informant reports. Each participant was tracked for an average of 11 years.

This analysis produced some telling results. Older adults with an obese-level BMI (30 or higher) at the beginning of the tracking period had a 31% greater risk of developing dementia throughout the study than those with a normal BMI (18.5-24.9).

Beyond these broad conclusions, the research team noticed some drastic differences between genders. Women with abdominal obesity (measured via waist size) specifically were 39% more likely to develop dementia than other studied females. This somewhat peculiar observation even held up after the study’s authors accounted for contributing risk factors (age, education, genetics, smoking habits, marital status, etc). 

However, no such relationship between only abdominal obesity and dementia risk was seen among male study participants.

“Dementia is one of the major health challenges of the 21st century that could threaten the successful aging of the population. Our findings suggest that rising obesity rates will compound the issue,” says study co-author Professor Andrew Steptoe, from the UCL Institute of Epidemiology & Health Care and Director of the English Longitudinal Study of Aging. “By identifying factors that may raise dementia risk that is influenced by lifestyle factors, we hope that a substantial portion, but admittedly not all, of dementia cases, can be prevented through public health interventions.”

Then, researchers decided to examine the influence of overall BMI and waist circumference. When this analysis was performed, it revealed a 28% increased risk of dementia for older adults of either gender with both a high BMI and large waist size.

So, how exactly does obesity promote dementia? There’s no clear answer to that question right now, but the study’s authors pointed to a few possible explanations. For example, obesity may worsen problems in vascular and metabolic pathways already linked to the buildup of amyloid proteins in the brain. Amyloid protein accumulation in the brain is a widely accepted indicator of Alzheimer’s.

“It is possible that the association between obesity and dementia might be potentially mediated by other conditions, such as hypertension or anticholinergic treatments. While not explored in this study, the research question of whether there an interactive effect between obesity and other midlife risk factors, such as hypertension, diabetes and APOE ε4 carrier status, in relation to dementia will be investigated in upcoming work,” comments first study author and MSc student Yuxian Ma, of the UCL Institute of Epidemiology & Health Care.

The full study can be found here, published in the International Journal of Epidemiology.