Sex- and Age-Related Variation in Somatic Symptom Systems Among Patients With First-Episode Anxiety Disorders: A Cross-Sectional Study and Exploratory Latent Class Analysis

Background Somatic symptoms are common in anxiety disorders, but it remains unclear whether sex differences reflect greater overall burden or distinct system distributions, and whether these associations vary with age. Methods This cross‑sectional study included 2,557 first‑episode anxiety disorder patients. Eight symptom systems were assessed. For six common systems, adjusted prevalence ratios were estimated using modified Poisson regression with nonlinear age modeling. Sex‑by‑age interactions were tested with Holm adjustment. Rare reproductive/endocrine symptoms were analyzed with bias‑reduced logistic regression. Latent class analysis was applied to the six common systems. Results Mean age was 48.2 years, 69.5% were female, and 82.4% had at least one somatic symptom. In primary models, females showed higher prevalence of circulatory, respiratory, and digestive symptoms, and lower prevalence of urinary, neurological, and motor symptoms (all Holm‑adjusted P < 0.001). Sex‑by‑age interactions were significant for all six systems. In expanded models, there was no clear association between sex and overall symptom presence or multisystem involvement. Latent class analysis identified four classes (circulatory‑dominant, respiratory‑dominant, digestive‑dominant, and neurological/low‑common‑system), with residual dependence between urinary and motor symptoms. Conclusions Sex was associated primarily with the distribution of somatic symptom systems rather than with overall multisystem burden, and these associations varied nonlinearly with age. The latent classes should be interpreted as exploratory system-level patterns requiring external validation rather than as established clinical subtypes.