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Background: Some studies have demonstrated an association between low and high body mass index (BMI) and an increased risk of dementia. However, only a few of these studies were performed in rural areas. Objective: This cross–sectional study investigated the associations between BMI and cognitive impairment among community–dwelling older adults from rural and urban areas. Methods: 8,221 older persons enrolled in the Hubei Memory & Ageing Cohort Study (HMACS) were recruited. Sociodemographic and lifestyle data, comorbidities, physical measurements, and clinical diagnoses of cognitive impairment were analyzed. Logistic regression was performed to assess the associations of BMI categories with cognitive impairment. A series of sensitivity analyses were conducted to test whether reverse causality could influence our results. Results: Being underweight in the rural–dwelling participants increased the risk of cognitive impairment. Being overweight was a protective factor in rural–dwelling participants aged 65–69 years and 75–79 years, whereas being underweight was significantly associated with cognitive impairment (OR, 1.37; 95% CI: 1.03–1.83; p < 0.05). Sensitivity analyses support that underweight had an additive effect on the odds of cognitive impairment and was related to risk of dementia. Interaction test revealed that the differences between urban/rural in the relationship between BMI and cognitive impairment are statistically significant. Conclusion: Associations between BMI and cognitive impairment differ among urban/rural groups. Older people with low BMI living in rural China are at a higher risk for dementia than those living in urban areas.

BackgroundThe correlation between cognitive function and lipid profiles, including total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and triglycerides, is inconsistent.AimsThis cross-sectional study investigated the association between serum lipid levels and the prevalence of cognitive impairment among community-dwelling older adults and explored this difference in association by gender and urban-rural residency.MethodsParticipants aged 65 and above in urban and rural areas were recruited between 2018 and 2020, selected from the Hubei Memory and Aging Cohort Study. Detailed neuropsychological evaluations, clinical examinations and laboratory tests were conducted in community health service centres. Multivariate logistic regression was used to analyse the correlation between serum lipid profiles and the prevalence of cognitive impairment.ResultsWe identified 1 336 cognitively impaired adults (≥65 years)—1 066 with mild cognitive impairment and 270 with dementia—from 4 746 participants. Triglycerides level was correlated with cognitive impairment in the total sample (χ2=6.420, p=0.011). In gender-stratified multivariate analysis, high triglycerides in males reduced the risk of cognitive impairment (OR: 0.785, 95% CI: 0.623 to 0.989, p=0.040), and high LDL-C in females increased the risk of cognitive impairment (OR: 1.282, 95% CI: 1.040 to 1.581, p=0.020). In both gender-stratified and urban-rural stratified multivariate analyses, high triglycerides reduced the risk of cognitive impairment in older urban men (OR: 0.734, 95% CI: 0.551 to 0.977, p=0.034), and high LDL-C increased the risk of cognitive impairment in older rural women (OR: 1.830, 95% CI: 1.119 to 2.991, p=0.016).ConclusionsThere are gender and urban-rural differences in the correlation of serum lipids with cognitive impairment. High triglycerides levels may be a protective factor for cognitive function in older urban men, while high LDL-C levels may be a risk factor for cognitive function in older rural women.

INTRODUCTIONThe prevalence and risk factors for subjective cognitive decline (SCD) and its correlation with objective cognition decline (OCD) among community‐dwelling older adults is inconsistent.METHODSOlder adults underwent neuropsychological and clinical evaluations to reach a consensus on diagnoses.RESULTSThis study included 7486 adults without mild cognitive impairment and dementia (mean age: 71.35 years [standard deviation = 5.40]). The sex‐, age‐, and residence‐adjusted SCD prevalence was 58.33% overall (95% confidence interval: 58.29% to 58.37%), with higher rates of 61.25% and 59.87% in rural and female subgroups, respectively. SCD global and OCD language, SCD memory and OCD global, SCD and OCD memory, and SCD and OCD language were negatively correlated in fully adjusted models. Seven health and lifestyle factors were associated with an increased risk for SCD.DISCUSSIONSCD affected 58.33% of older adults and may indicate concurrent OCD, which should prompt the initiation of preventative intervention for dementia.Highlights SCD affects 58.33% of older adults in China. SCD may indicate concurrent objective cognitive decline. Difficulty finding words and memory impairments may indicate a risk for AD. The presence of SCD may prompt preventative treatment initiation of MCI or dementia. Social network factors may be initial targets for the early prevention of SCD.

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