Faster BMI decline after mild cognitive impairment diagnosis may indicate dementia

A faster decline in BMI and a lower BMI as a result may indicate the need for cognitive assessments prior to the possibility of incident dementia, per a study published in JAMA Psychiatry.

“Mild cognitive impairment affects 16% to 20% of older adults, and more than one-third of individuals with MCI go on to develop dementia over 5 or more years,” Jie Guo, MPH, of the aging research center and department of neurobiology at the Karolinska Institute in Stockholm, and colleagues wrote. “Therefore, identifying risk factors for MCI may help to slow or prevent the development of dementia.”

Guo and colleagues sought to assess the long-term BMI trajectories preceding incident MCI and dementia and to explore whether they are associated with brain pathologies.

The Rush Memory and Aging Project (MAP) was an ongoing community-based cohort study that included 1,390 cognitively intact participants (mean age 78.4 years, 76.5% female) at baseline with annual follow-up from October 1997 to December 2020. BMI was calculated using height and weight measured at baseline and subsequent follow-ups, while incident MCI and dementia were diagnosed following standard criteria. Neuropathological assessments (including global Alzheimer’s disease and vascular pathology) were performed for autopsies. Data were analyzed from August 2021 to February 2022 using mixed-effect models.

Results showed, in the analysis of BMI trajectories before MCI (n = 939), during the follow-up, 371 participants (39.5%) developed MCI, of whom 88 (23.7%) progressed to dementia. Those who developed MCI were older, consumed less alcohol, had a lower BMI and were more likely to be apolipoprotein E (APOE) 4 carriers compared with those who remained cognitively intact over follow-up. Those who developed dementia were older, had a lower level of physical activity (median [IQR] activity, 1.0 [0-2.5] h/week vs 1.8 [0.2-3.8] h/week) and were more likely to be APOE 4 carriers than those who were dementia-free. Compared with participants who remained cognitively intact, in those with incident MCI, BMI tended to decline earlier and faster. From 7 years before diagnosis, people with incident MCI had an associated significantly lower BMI (mean difference, 0.96; 95% CI, 1.85 to 0.07) than those who were cognitively intact.

Data additionally revealed, in analysis of BMI trajectories before autopsy (n = 358), BMI was associated with a faster decline among participants with a high burden of global Alzheimer disease pathology ( for pathology×time highest vs lowest tertile, 0.14; 95% CI, 0.26 to 0.02) or vascular pathology ( for pathology×time2 highest vs lowest tertile, 0.02; 95% CI, 0-0.05).

“These findings highlight the importance of monitoring weight change regularly among older adults, as a faster decline in BMI and a lower BMI may indicate the need for cognitive assessments,” Guo and colleagues wrote.