Residential proximity to major roadways and prevalent diabetes in older adults: a cross-sectional study based on CLHLS

Abstract Background Diabetes is a major global public health concern, and China bears a growing diabetes burden that calls for targeted prevention. High-income country studies link residential proximity to roadways with diabetes, yet evidence from developing countries is limited. This population-based analysis delivers robust evidence for environmental health interventions and age-friendly urban planning for Chinese older adults. Methods We used nationally representative data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). After excluding those with missing values for key variables, 4,702 adults aged ≥ 65 years entered the complete-case primary analysis. Roadway proximity and diabetes status were self-reported. Logistic regression models calculated ORs and 95% CIs with sequential adjustment for demographic, lifestyle and health covariates. Stratified analyses and interaction tests assessed effect modification. Results The sample included 4,702 participants (mean age 78.7 years; 55.1% men) with 13.9% diabetes prevalence. Fully adjusted ORs were 1.36 (95% CI:1.11–1.67) for residents < 100 m from major roadways and 1.31 (95% CI:1.03–1.66) for those 100–300 m away (reference group: > 300 m). A statistically significant overall trend test was obtained, yet the exposure–response relationship across distance strata was non-monotonic ( P for trend < 0.05). A borderline interaction existed between roadway proximity and smoking ( P for interaction = 0.044). Stratification showed a positive association among non-smokers (OR = 1.29, 95% CI:1.06–1.56) but no significant link in smokers (OR = 0.82, 95% CI:0.48–1.42). Given the marginal P -value and small smoking subgroup sample (wide CIs), this interaction needs cautious interpretation and verification in larger cohorts. Conclusion This cross-sectional study found a significant association between proximity to major roadways and prevalent diabetes in Chinese older adults. Roadway proximity acts as a composite surrogate marker of traffic hazards, neighborhood socioeconomic deprivation and built environments, rather than merely traffic pollution or noise. These findings guide future environmental and health equity research on seniors. Longitudinal studies with objective exposure measurements are required to confirm our results and inform age-friendly urban design and geriatric health policies.