Lower BMI may signal early cognitive decline in older people

Body mass index (BMI), a measure derived from a person’s weight and height, may hold clues about the early stages of cognitive decline. A recent study from Karolinska Institutet found that BMI tends to drop significantly several years before a diagnosis of mild cognitive impairment (MCI), a condition that often precedes dementia.

The researchers analyzed the BMI trends of 1,390 older adults with an average age of 78.4 years, most of whom were women (76.5%). They tracked participants over time to observe changes in BMI leading up to the onset of MCI and dementia.

The findings revealed that individuals who eventually developed MCI experienced a noticeable decline in BMI starting about seven years before their diagnosis. This pattern was not seen in participants who remained cognitively healthy.

Interestingly, while BMI decline was a common precursor to MCI, the rate of BMI decline was similar whether or not those with MCI went on to develop dementia.

For a subset of 358 participants who underwent autopsies, the researchers found a connection between BMI decline and brain pathology. Specifically, participants with more severe signs of Alzheimer’s disease or vascular brain disease experienced faster drops in BMI.

This suggests that underlying brain changes linked to Alzheimer’s or vascular conditions may contribute to weight loss well before cognitive symptoms become apparent.

The study’s authors emphasize the importance of further research to better understand this relationship. For instance, advanced imaging techniques like positron emission tomography (PET) scans could help clarify how changes in BMI correlate with the development of Alzheimer’s pathology or other brain abnormalities over time.

These findings highlight the potential of BMI as an early indicator of cognitive decline. Monitoring unexplained weight loss in older adults may provide an opportunity for earlier intervention in conditions like MCI and dementia.

However, more research is needed to fully understand how and why BMI changes occur in the years leading up to these diagnoses.

The study, led by Jie Guo and colleagues, was published in JAMA Psychiatry. It adds to a growing body of evidence suggesting that physical changes, such as weight loss, may offer important clues about brain health in aging populations.

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