Current anti-depressant use is associated with cortical bone deficits and reduced physical function in elderly women

Background: Anti-depressants, particularly selective serotonin reuptake inhibitors (SSRIs), are associated with an increased risk of fracture. The mechanism is unclear and may be due to effects on bone metabolism, muscle strength, falls or other factors. It is unknown if serotonin norepinephrine reuptake inhibitors (SNRIs) have similar effects. Methods: We compared musculoskeletal health in current female anti-depressant users and non-users from a population-based multiethnic (35.6% black, 22.3% white and 42.1% mixed) cohort study of adults 65 years old in New York (N = 195) using dual x-ray absorptiometry (DXA), trabecular bone score (TBS), vertebral fracture assessment (WA), high resolution peripheral quantitative computed tomography (HR-pQCT), body composition, and grip strength. Results: Current anti-depressant users were more likely to be white than non-while (OR 1.9, 95% CI 1.2-2.9) and were shorter than non-users, but there were no differences in age, weight, BMI, physical activity, calcium/ vitamin D intake, falls or self-rated health. There were more pelvic fractures in current vs. non-users (7.1% vs. 0%, p = 0.04). Age- and weight-adjusted T-score by DXA was lower in current users at the 1/3-radius (- 1.6 +/- 1.1 vs. -1.0 +/- 1.4, p = 0.04) site only. There was no difference in TBS, vertebral fractures or fat/lean mass by DXA. Age- and weight-adjusted grip strength was 13.3% lower in current users vs. non-users (p = 0.04). By HR-pQCT, age- and weight-adjusted cortical volumetric BMD (Ct. vBMD) was 4.8% lower in users vs. non-users at the 4% radius site (p = 0.007). A similar cortical pattern was seen at the proximal (30%) tibia. When assessed by anti-depressant class, deteriorated cortical microstructure was present only in SSRI users at the radius and only in SNRI users at the proximal tibia. Conclusions: Anti-depressant use is associated with cortical deterioration and reduced physical function, but effects may be class-specific. These findings provide insight into the mechanism by which anti-depressants may contribute to the increased fracture risk in older women.