The following is a summary of “Body Mass Index Trajectories Preceding Incident Mild Cognitive Impairment and Dementia” published in the October 2022 issue of Psychiatry by Guo et al.

Uncertainty exists over the body mass index (BMI) trajectories prior to moderate cognitive impairment (MCI) and throughout the transition from MCI to dementia. For a study, researchers sought to evaluate the long-term BMI trends preceding incident MCI and dementia and investigate if they are connected to brain diseases.

It was an ongoing community-based cohort research, the Rush Memory and Aging Project (MAP). Participants in the research ranged in age from 60 to 90 years at baseline, and they were followed up every year until December 2020. (maximum follow-up of 22 years). Participants had brain autopsies performed throughout the follow-up. Using mixed-effect models, data were examined between August 2021 and February 2022. BMI was estimated using baseline and follow-up measurements of height and weight. Following accepted criteria, incident MCI and dementia were identified. Autopsies were subjected to neuropathological evaluations (including vascular pathology and worldwide Alzheimer’s disease).

The study comprised 1,390 individuals, with 1,063 women (76.5%) and an average age of 78.4 [6.5] years. In the examination of BMI trajectories before MCI (n = 939), 371 patients (39.5%) developed MCI during the follow-up (median [IQR] duration, 6 [3-9] years), and 88 (23.7%) of those participants proceeded to dementia. In comparison to those who maintained cognitive health over time, those who developed MCI were older (mean [SD] age, 79.6 [5.9] years vs. 76.9 [6.6] years), drank less alcohol (median [IQR] consumption, 0 [0-5.8] g/day vs. 1.1 [0-6.9] g/day), had a lower BMI (mean [SD], 27.2 [4.9] vs. 28.2 [5.9]) and were more likely to be apolipoprotein E (APOE) ε4 carriers (89 of 371 [24.0%] vs. 98 of 568 [17.3%]) compared with those who remained cognitively intact over follow-up. In comparison to those who did not develop dementia, those who did so were older (mean [SD] age, 81.0 [5.2] years vs. 79.1 [6.0] years), engaged in less 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 carry the APOE ε4 gene than those who were dementia-free (33 of 88 [37.5%] vs. 56 of 283 [19.8%]). In individuals with incident MCI, BMI tended to fall earlier and more quickly than those with cognitively intact aging. People with incident MCI had a substantially lower BMI (mean difference, −0.96; 95% CI, −1.85 to −0.07) compared to cognitively intact individuals starting 7 years before their diagnosis. The slopes of BMI decrease did not substantially differ between those who did and did not acquire dementia among individuals with incident MCI (β, −0.03; 95% CI, −0.21 to 0.15). In the analysis of BMI trajectories before autopsy (n = 358), participants with a high burden of global Alzheimer’s disease pathology (β for pathology × time highest vs. lowest tertile, −0.14; 95% CI, −0.26 to −0.02) or vascular pathology (β for pathology × time2 highest vs. lowest tertile, 0.02; 95% CI, 0-0.05) showed a faster declination with BMI.

The findings of the cohort research indicated that considerably decreased BMI started to occur in cognitively healthy individuals starting about seven years before MCI diagnosis. Following an MCI diagnosis, BMI drops equally in those who have dementia and those who do not. High brain abnormalities may cause the drop in BMI prior to dementing illnesses.