Gender and age differences in the associations between cortical thickness and hand osteoarthritis severity: data from the Osteoarthritis Initiative.

Objective: To evaluate gender differences in the association between metacarpal cortical thickness (T _cort )-a surrogate for bone density-and severity of radiographic hand osteoarthritis (HOA) in a longitudinal observational study.
Method: Hand radiographs of 3575 participants (2039 F/1536 M) from the Osteoarthritis Initiative were assessed at baseline and 48 months. A reader used a semi-automated software tool to calculate T _cort , a measurement of the cortical thickness, for metacarpals 2-4. Average T _cort at baseline and change in T _cort from baseline to 48 months was determined and stratified by gender and age for 7 5-year age groups. Spearman's rank correlation coefficients were calculated for the association of baseline T _cort and 2 measures of baseline HOA severity: the sum of Kellgren-Lawrence (KL) grade and total number of joints with radiographic HOA. Longitudinally, logistic regression was used to assess the relationship of T _cort loss to new finger joint radiographic HOA, increase in KL grades, and incident hand pain.
Results: Male T _cort was higher than females. Significant correlations between T _cort and radiographic severity were noted for women but not men, with stronger associations among women >60 years (rho = -0.25; 95% confidence interval (CI) = -0.31 to -0.19). Statistically significant associations were seen between T _cort change and radiographic osteoarthritis change among women but not men, with substantial gender differences for T _cort change, particularly ages 50 to 70 years (p < 0.01; e.g., T _cort change ages 55 to <60: males = -0.182 (0.118), females = -0.219 (0.124)).
Conclusion: We found significant HOA-related gender differences in T _cort , suggesting the involvement of female bone loss during and after menopause.
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