Objective To analyze the HIV infection status, risk behavior patterns, and influencing factors in ≥50 years old men with non-marital heterosexual behavior in Sichuan province.

Methods Based on sentinel surveillance data in this population in Sichuan province from 2019 to 2024, a consecutive cross-sectional survey was conducted. Sociodemographic characteristics, behavioral information, HIV and syphilis infection status of this population were collected via questionnaire survey and serological testing. χ² test, trend analysis, and multivariate logistic regression model were used to analyze the influencing factors.

Results In 49 838 surveyed individuals, 68.37% were aged ≥60 years and 91.90% had education level of junior high school education. The overall HIV antibody positive rate was 0.52%, showing a significant downward trend (trend χ²=12.678, P<0.05). The HIV related knowledge awareness rate increased to 88.16%. However, the condom use rate were low: consistent condom use with spouses/regular partners was only 5.22%, consistent condom use in commercial sex was 24.96%, and consistent condom use in casual sex was 23.34%. Multivariate analysis identified suffering from syphilis adjusted odds ratio(aOR)=4.87, living alone (aOR=3.12), being unmarried/divorced/widowed (aOR=2.12), and inconsistent condom use in commercial sex (aOR=1.89) as independent risk factors for HIV infection. Education level of high school or above was a protective factor (aOR=0.52).

Conclusion Although the HIV infection rate in ≥50 years old with non-marital heterosexual behavior in Sichuan province showed 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.