Sex differences in factors affecting spinopelvic sagittal alignment and balance: a cross-sectional observational study in a Japanese community

Understanding how age and sex affect spinopelvic sagittal alignment is important for preventing the progression of adult spinal deformity and optimizing treatment. Here, we analyzed sex differences in age-related changes in spinopelvic sagittal alignment and balance in a Japanese community. Healthy adults (210 men and 300 women) ranging in age from their 20-80 s who participated in a general population health examination were categorized into age groups by decade according to sex. The association between changes in sagittal spinal alignment and balance, vertebral fracture, bone mineral density, bioelectrical impedance analysis, handgrip strength, and gait speed was investigated. In women, we found increased thoracic kyphosis in the 60s and pelvic retroversion in the 70s. In men, slight changes in local sagittal alignment were observed with age. Multiple linear regression analyses revealed that sagittal balance was associated with both age and vertebral fractures in men but only with age in women. Age-related changes in spinopelvic sagittal alignment differed between men and women, with men exhibiting nonstructural changes and women experiencing structural changes. In men, both age and vertebral fracture contributed to sagittal imbalance, whereas in women, only aging was associated with sagittal imbalance.