Household Income and Sexual Activity Patterns Among Japanese Men: A Latent Class Analysis of a Nationwide Survey.

OBJECTIVES: To identify latent classes of sexual activity among Japanese adult men using multiple sexual behavior indicators and to investigate their associations with household income. METHODS: This cross-sectional study analyzed data from a 2023 nationwide Internet-based survey of 5 735 Japanese men aged 20-79 years. Latent class analysis used six indicators: Sexual intercourse frequency, masturbation frequency, morning erection frequency, and International Index of Erectile Function items 6, 11, and 12. Household income data were available for 4 824 men, who were categorized into low (<¥4 million/year), middle (¥4 to <¥8 million/year), or high (≥¥8 million/year) income groups. RESULTS: Four latent classes were identified: Low desire/inactive (Class 1, 37.3%), high desire/non-coital (Class 2, 25.8%), moderate desire/sexually active (Class 3, 14.7%), and high desire/high-function active (Class 4, 22.1%). Higher household income was independently associated with Classes 3 and 4, with dose-response relationships, but not with Class 2. The overall income-by-marital-status interaction was significant (p = 0.0004), whereas the class-specific interaction was significant only for Class 3 (p = 0.021) and not for Class 4 (p = 0.255). These post hoc interaction findings were considered exploratory. Sensitivity analyses yielded consistent results. CONCLUSIONS: Approximately one-quarter of Japanese men belonged to a class characterized by moderate-to-high sexual desire and relatively frequent morning erections despite predominantly little or no intercourse. Household income was associated with intercourse-involving classes but not with Class 2. These findings support a multidimensional assessment of sexual health and warrant further research on socioeconomic factors associated with partnered sexual activity.