ObjectiveTo systematically review the association between overweight, obesity, abdominal obesity, and cognitive impairment in the elderly. MethodsThe CNKI, WanFang Data, VIP, CBM, PubMed, Web of Science, Embase, and Cochrane Library databases were electronically searched for studies on the relationship between overweight, obesity/abdominal obesity, and cognitive impairment in the elderly from their inception to July 2024. Two researchers independently screened the literature, extracted data, and assessed the risk of bias of the included studies. Meta-analysis was performed using Stata 15.0 software. ResultsA total of 38 studies involving 1 783 087 subjects were included. Meta-analysis results showed that compared with normal-weight individuals, overweight (OR=0.96, 95%CI 0.91 to 1.02, P=0.201) was not statistically significant in the risk of CI in the elderly. Obesity (OR=1.14, 95%CI 1.02 to 1.28, P=0.03) and abdominal obesity (OR=1.16, 95%CI 1.11 to 1.21, P<0.001) may be risk factors for CI in the elderly. Subgroup analysis was conducted based on study type, BMI standards, cognitive diagnostic standards, national development level, abdominal obesity diagnostic standards, and follow-up time. Among the subgroups analyzing the correlation between overweight and CI in the elderly, follow-up time ≤ 5 years (OR=0.68, 95%CI 0.58 to 0.80) showed a lower proportion of CI compared to other follow-up periods. In the subgroups analyzing the correlation between obesity and CI in the elderly, follow-up time ≤ 5 years (OR=0.71, 95%CI 0.50 to 1.01) was not statistically significant compared to other follow-up periods. For abdominal obesity, a significant association with increased CI risk in the elderly was found only in the subgroup with a follow-up time of 5-10 years (OR=1.21, 95%CI 1.15 to 1.27), compared with other follow-up periods. ConclusionCurrent evidence suggests that obesity and abdominal obesity may increase the risk of CI in the elderly. Proper weight management is crucial for preventing and delaying the progression of CI in the elderly.