Association of cardiometabolic multimorbidity and high-risk lifestyle behaviours with subjective cognitive decline: baseline findings from the China ageing and health survey.

Background: Previous studies have reported associations between subjective cognitive decline (SCD) and both cardiometabolic multimorbidity (CMM, the co-occurrence of ≥2 cardiometabolic diseases (CMDs), including coronary heart disease, stroke, and diabetes) and lifestyle factors (LFs). While urban-rural disparities in health care access and risk factor distribution are well known, variations in these associations and the interaction between LFs and CMM among individuals with SCD in non-high-income countries remain unclear. This study aimed to investigate the association of CMM and LFs with SCD in older adults living in rural or urban areas in China. Methods: This population-based study included 41 859 older adults (median age 72.0 years; 52.48% female; 38.95% rural) from 31 provincial regions in China. Subjective cognitive decline was assessed using the Eight-Item Informant Interview to Differentiate Aging and Dementia. High-risk LFs included tobacco smoking, alcohol drinking, unhealthy diet, low physical activity, and unhealthy body shape. Cardiometabolic diseases were assessed by self-reported physician diagnoses. Lifestyle factors were collected via interviewer-administered questionnaires. Logistic regression, relative excess risk due to interaction and attributable proportion were used to assess associations and additive interactions. Results: Cardiometabolic multimorbidity (odds ratio (OR) = 2.36; 95% confidence intervals (CI) = 2.10, 2.66) and the number of CMDs (OR = 1.49; 95% CI = 1.43, 1.56) were significantly associated with an increased likelihood of SCD. Gradients in the associations between the number of high-risk LFs and SCD were observed (P < 0.05), except for five high-risk LFs. These associations were stronger in rural than in urban residents (P for interaction <0.05). Significant additive interaction was found between high-risk LFs and CMM (relative excess risk due to interaction = 1.63, 95% CI = 0.67, 2.59; attributable proportion = 0.54, 95% CI = 0.22, 0.86) for SCD. Conclusions: The coexistence of CMM and high-risk LFs exhibited an additive association with SCD. These findings highlight the need for integrated management of modifiable CMDs and lifestyle risk factors, and may inform prioritisation of rural populations.