framingham heart study

Weight Patterns over Lifespan May Predict Dementia Risk

Monitoring weight patterns across the lifespan could provide vital opportunities to reduce dementia risk through early intervention.

About 1 in 10 Americans and more than 55 million people worldwide have dementia, and these numbers are only expected to grow in the next three decades. Previous studies have linked obesity—a worsening epidemic—with an increased risk of dementia, but the data indicate that this relationship may fluctuate over one’s lifespan. 

Now, a new study led by a School of Public Health professor has found that an overall decline in body mass index (BMI), an indicator of obesity, is associated with increased dementia risk, but people whose BMI increases through late mid-life and then declines in older age are even more likely to develop the disease. 

Published in Alzheimer’s & Dementia, a journal of the Alzheimer’s Association, the study found thathigher risk of dementia was associated with BMI scores that increased among people ages 40 to 49 years old, and then began declining after age 50. Weight loss in itself is a known risk factor for dementia, and the new analysis suggests that dementia-related weight loss could begin as early as 50 years old.

These findings also suggest that monitoring weight patterns across the lifespan could provide vital opportunities to reduce dementia risk through early intervention.

“These findings are important because previous studies that looked at weight trajectories didn’t consider how patterns of weight gain/stability/loss might help signal that dementia is potentially imminent,” says study senior and corresponding author Rhoda Au, professor of epidemiology at SPH, and professor of anatomy and neurobiology at Boston University Chobanian & Avedisian School of Medicine. 

For the study, Au and colleagues examined changes in weight and BMI among 2,405 participants in the Framingham Heart Study, the country’s oldest heart disease study, run by Boston University and the National Heart, Lung, and Blood Institute. The study continues to gather data on a variety of biological and lifestyle risk factors and disease outcomes across three generations of participants, and it is one of a few cohort studies that include participants who have been followed for dementia beginning as younger middle-age adults.

The researchers measured the participants’ weight every 2-4 years for 39 years to assess which BMI decline patterns were significantly associated with increased risk of dementia. Interestingly, while examining subdivided groups of participants’ whose BMI declined from mid to later-life, the team also found that neither consistent BMI decline during mid-life, nor stable BMI during mid-life with decline in older years, were associated with an increased risk of dementia—further suggesting that only mid-life fluctuation in BMI may significantly increase this risk.

The researchers say that future life-course studies are needed to determine whether this potential increase in dementia risk apples to younger adults, as well. Although dementia is “not necessarily inevitable,” Au says, monitoring weight patterns could offer opportunities to implement interventions that could delay dementia onset.