Weight loss and significant body weight variability (BWV) in older adults is associated with faster rates of cognitive decline over time, according to study results published by The Obesity Society.
Researchers conducted a longitudinal study from 1993 and 2016, using the Health and Retirement Study. Individuals without a history of cognitive illness were included in the study.
Participants reported their body weight biennially. Researchers calculated body weight change and BWV for each participant. Body weight change was grouped into 3 categories, including stable weight (-0.76 to 0.57 kg/year), weight loss (<-0.76 kg/year), and weight gain (>0.57 kg/year). BWV was also grouped into 3 groups, including small (<2.18 kg), moderate (2.18-4.06 kg), and large (>4.06 kg).
The results were adjusted for confounding factors including differences in socioeconomic factors, demographics, lifestyle factors, age, sex, and race.
The total cohort included 10,340 individuals, with a mean age of 68 (SD, 9.8) years; 58.7% were women. The median follow-up was 12 years (IQR, 4-18 years) and the median number of body weight measurements was 9 (IQR, 6-12). Of the total cohort, 6933 (67%) had stable weight, 2063 (20%) had weight loss, and 1343 (13%) had weight gain. The average rate of cognitive decline was reported as a z-score change of -0.052 (SD, 0.051) per year.
The researchers found that those who had weight loss vs those who had stable weight had a faster rate of cognitive decline, with a mean difference of -0.023 (95% CI, -0.027 to -0.019). However, individuals with weight gain had a slower rate of cognitive decline. (β=0.006 [95% CI, 0.003-0.009]). A large vs small BWV was also associated with a faster rate of cognitive decline (β=-0.003 [95%, CI, -0.006 to -0.0002]). No significant associations were found between cognitive decline and moderate BWV.
In the subgroup analysis, the researchers observed associations between weight loss and faster rates of decline in episodic memory (β=-0.026 [95% CI, -0.031- to -0.021]) and working memory (β=-0.013 [95% CI, -0.017 to -0.009]). Large BWV was also related to a faster decline in working memory (β=-0.007 [95% CI, -0.011 to -0.004]), but lacked an association with episodic memory.
Limitations of the study included the fact that weight was self-reported by participants, which may have had a potential risk for bias; and individuals with cognitive impairment might have had a higher risk for weight loss and BWV, which could have altered the significance of the results.
The study authors concluded that “…both weight loss and large BWV were independently associated with faster cognitive decline emphasized the importance of long-term dynamic body weight monitoring rather than simply focusing on  aspect of body weight.”
Zhou T, Chen H, Huang Y, et al. Longitudinal body weight dynamics in relation to cognitive decline over two decades: a prospective cohort study. Obesity (Silver Spring). 2023;31(3):852‐860. doi:10.1002/oby.23671