Higher systemic immune-inflammation index associates with vertebral marrow proton density fat fraction in postmenopausal women.

Abstract

Introduction: The systemic immune-inflammation index (SII) may influence bone homeostasis through inflammatory modulation. Although bone marrow adipocytes regulate bone metabolism via adipokine secretion, their interaction with SII remains unexplored. We investigated the SII-marrow adiposity relationship in postmenopausal women.

Materials and methods: This retrospective study included 187 postmenopausal women. Lumbar spine MRI using chemical shift encoding generated proton density fat fraction (PDFF) maps, with bone mineral density (BMD) measured by dual x-ray absorptiometry. The relationship between SII and marrow PDFF was evaluated through multivariable-adjusted linear regression, smooth curve fittings, and threshold analysis.

Results: The results revealed a negative correlation between marrow PDFF values and BMD (r = - 0.438, P < 0.001). After accounting for age, time since menopause, body mass index, physical activity, C-reactive protein, interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and BMD in the regression analysis, each unit increase in SII was found to be inked to an increase of 0.247 (β = 0.247; 95% confidence interval [CI], 0.212 to 0.281; P <0.001) in PDFF. After converting SII to a categorical variable (quartiles), participants in the highest SII quartile had a 16.8% higher vertebral marrow PDFF than those in the lowest SII quartile (β = 16.753, 95% CI: 11.036-18.522, P <0.001). Furthermore, a curvilinear relationship and threshold effect were also identified. Turning point was identified at the SII value of 441 on the adjusted smooth curve.

Conclusions: SII levels were positively associated with marrow adiposity in postmenopausal women.