Systemic inflammation partially mediates the association between lipid accumulation and osteoarthritis in normal BMI adults.

This study aims to investigate the association between lipid accumulation product (LAP) levels and osteoarthritis (OA) in participants with normal BMI, and the potential role of the systemic inflammation response index (SIRI) in this association. Participants with normal BMI from the national health and nutrition examination survey (NHANES) database (2009-2018) were included. A weighted multivariable logistic regression was used to analyze the association between LAP levels and OA, and mediation analysis was applied to explore the role of SIRI in this relationship. Among 2408 participants with normal BMI, the average age was 43.85 ± 17.68 years, with 1240 (55%) women, and 210 (8.72%) participants recorded as having OA. Compared with the first quartile, the highest quartile of LAP levels was significantly associated with higher OA prevalence and higher SIRI levels [OA (AOR = 1.969, 95% CI 1.035-3.745, P = 0.039); SIRI (AOR = 1.174, 95% CI 1.029-1.489, P = 0.029)], especially in young women. Compared with the first quartile, the highest quartile of SIRI levels was significantly associated with higher OA prevalence [AOR = 1.542, 95% CI 1.010-2.356, P = 0.045], particularly in young women. The highest quartile of LAP levels was significantly associated with higher OA prevalence, with a portion of the association mediated by SIRI (10.30%), with mediation proportions of 8.92% in younger individuals and 8.69% in women. Even with normal BMI, high LAP levels are significantly associated with a higher prevalence of OA, with part of the association mediated by systemic inflammation, especially in young women.