Is kyphosis related to mobility, balance, and disability?

Abstract

Objective: The aim of this study was to determine the association of increased kyphosis with declines in mobility, balance, and disability among community-living older adults.

Design: The 18-mo follow-up visit data from 2006 to 2009 for 620 participants from the population-based Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly Boston Study of older adults was used. Cross-sectional multivariable regression analyses were performed to assess the relationship between kyphosis (measured using the kyphosis index) and measures of mobility performance (Short Physical Performance Battery), balance (Berg Balance Scale score), and disability (self-reported difficulty walking a quarter of a mile or climbing a flight of stairs). The authors then evaluated the men and the women separately. Adjustment variables included demographic factors (age, sex, race, and education), body mass index, self-rated health, comorbidities (heart disease, diabetes, stroke, and depressive symptoms), back pain, knee pain, and falls self-efficacy.

Results: After full adjustment, greater kyphosis index was associated with lower Short Physical Performance Battery scores (adjusted β = -0.08, P = 0.01) but not with lower Berg Balance Scale (adjusted β = -0.09, P = 0.23) or self-reported disability (adjusted β = 1.00; 95% confidence interval, 0.93-1.06) scores. In sex-specific analyses, kyphosis index was associated with only the Short Physical Performance Battery in the women.

Conclusions: Greater kyphosis is associated with poorer mobility performance but not with poorer balance or self-reported disability. This association with the Short Physical Performance Battery was observed only among the women. Mechanisms by which increased kyphosis influences physical performance should be explored prospectively.

Figure 1

The curvature of the spine is measured by placing a flexicurve ruler along the participant’s spine and measuring the curve from C7 to the lumbosacral junction (represented here by LS). A horizontal line is then drawn from C7 to LS, and the height and width of the thoracic portion of the curve is measured. The kyphosis index (KI) is calculated by dividing the thoracic height by the thoracic width and multiplying the result by 100 (KI = (H/W)*100).

Figure 2

In Figures (a) and (b), fully adjusted least-squares means and 95% confidence intervals of (a) Short Physical Performance Battery (SPPB) scores and (b) Berg Balance Scale (BBS) scores by kyphosis index (KI) quintiles in multivariable linear regression models are shown. In Figure (c), the fully adjusted odds ratios of multivariable logistic regression model predicting self-reported disability for all participants is shown; Quintile 1 is used as the referent in (c). Full adjustment includes adjustment for demographic factors (age, gender, race, and education), BMI, self-rated health, comorbidities (heart disease, diabetes, stroke, depressive symptoms), back pain, knee pain and falls self-efficacy. In these models, the entire study population was used.

Figure 2

In Figures (a) and (b), fully adjusted least-squares means and 95% confidence intervals of (a) Short Physical Performance Battery (SPPB) scores and (b) Berg Balance Scale (BBS) scores by kyphosis index (KI) quintiles in multivariable linear regression models are shown. In Figure (c), the fully adjusted odds ratios of multivariable logistic regression model predicting self-reported disability for all participants is shown; Quintile 1 is used as the referent in (c). Full adjustment includes adjustment for demographic factors (age, gender, race, and education), BMI, self-rated health, comorbidities (heart disease, diabetes, stroke, depressive symptoms), back pain, knee pain and falls self-efficacy. In these models, the entire study population was used.