Objectives To analyze the HIV infection status, risk behavior patterns, and influencing factors among men aged 50 years and above engaging in non-marital heterosexual behavior in Sichuan Province, China.

Methods Based on sentinel surveillance data of men aged ≥50 years with non-marital heterosexual behavior in Sichuan Province from 2019 to 2024 , a consecutive cross-sectional survey was conducted. Sociodemographic characteristics, behavioral information, and HIV/syphilis infection status were collected via questionnaires and serological testing. Chi-square tests, trend analysis, and multivariate logistic regression were used to analyze factors influencing infection.

Results Among 49,838 surveyed individuals, 68.37% were aged ≥60 years and 91.90% had ≤junior high school education. The overall HIV antibody positive rate was 0.52%, showing a significant downward trend (trend χ²=14.27,P<0.05).HIV knowledge awareness rate increased to 88.16%. However, condom use rates were generally low: consistent condom use with spouses/stable partners was only 5.22%,consistent condom use during commercial sex was 24.96% , and consistent condom use during casual sex was 23.34%.Multivariate analysis identified syphilis positivity (aOR = 4.87), living alone (aOR =3.12), being unmarried/divorced/widowed (aOR =2.12), and inconsistent condom use during commercial sex (aOR =1.89) as independent risk factors for HIV infection... An education level of high school or above was a protective factor (aOR = 0.52).

Conclusion Although the HIV infection rate among men aged ≥50 years with non-marital heterosexual behavior in Sichuan Province shows a declining trend, a significant "knowledge-behavior gap" exists. It is essential to develop age-friendly intervention tools targeting those living alone and with low education levels, optimize testing services, and strengthen integrated syphilis control measures.