Relationship of total sagittal spinal alignment index of thoracic kyphosis and lumbar lordosis with physical function in community-dwelling older adults.

Background: Overall spinal curvature is evaluated by calculating the difference between the angles of lumbar lordosis (LL) and thoracic kyphosis (TK) and is expressed as LL minus TK (LL-TK). It is unclear whether LL-TK is associated with physical function in community-dwelling older adults and whether it is more relevant than TK or LL alone.

Objective: This study aimed to identify whether LL-TK is associated with physical function in community-dwelling older adults, and whether it is strongly associated than TK or LL alone.

Methods: The participants comprised 1,674 community-dwelling older adults who underwent physical assessments (women, n = 1,099; mean age, 67.4 ± 5.3 years). As spinal alignment indices, TK and LL were measured using skin surface methods, and LL-TK was calculated as the difference between them. Decreased LL-TK indicated increased overall spinal curvature. Physical function was determined by measuring single-leg standing, five-times chair-stand, and usual gait speed. Stepwise multiple regression analyses were performed with each physical function as the dependent variable and spinal alignment indices as the independent variables, with adjustments.

Results: Multiple regression analyses showed that single-leg standing (β = 0.092, 95% confidence interval [CI] = 0.071 to 0.214, p < .001) and five-times chair-stand (β=-0.142, 95% CI = -0.037 to -0.019, p < .001) were significantly associated with LL-TK, but not LL. Both LL-TK (β = 0.121, 95% CI = 0.001 to 0.004, p < .001) and LL (β = 0.087, 95% CI = 0.001 to 0.003, p = .003) were significant determinants of usual gait speed.

Conclusions: This study showed that decreased LL-TK may be associated with poor physical function. This association may be stronger than that observed for TK or LL alone.