The cross-sectional relationship of hemoglobin levels and functional outcomes in women with self-reported osteoarthritis: results from the Women's Health Initiative.

OBJECTIVES: Gastrointestinal blood loss is a recognized complication of the use of nonsteroidal anti-inflammatory drugs (NSAIDS) in patients with arthritis. We examined the cross-sectional relationship of patient-reported outcomes of overall health, physical function, vitality, and quality of life to hemoglobin (hgb) levels in postmenopausal women with self-reported osteoarthritis to determine whether hgb levels as potential markers of chronic blood loss were associated with these functional outcomes.
METHODS: Postmenopausal women (N = 64,850) with self-reported osteoarthritis (srOA) at baseline in the Women's Health Initiative study, excluding participants with chronic or hemolytic diseases associated with anemia, had hgb levels measured and completed Short-Form Health Surveys. General linear models analysis adjusting for potential confounders was performed.
RESULTS: A nonlinear plateauing relationship between hgb levels and functional outcomes was found. Participants with srOA had statistically significantly worse overall health, physical function, and vitality, but not quality of life, for each gram of hgb below 14 g/dL, compared with those with hgb 14 g/dL (P < 0.001). Participants with srOA taking NSAIDS had worse functional outcomes for each level of hgb compared with those not reporting NSAIDS use.
CONCLUSIONS: In cross-sectional analyses of postmenopausal women with srOA, differences in hgb levels are related to differences in functional outcomes of overall health, physical function, and vitality at clinically important levels. Prospective studies evaluating whether changes in hgb levels result in changes in functional outcomes in participants with osteoarthritis are needed to confirm of our findings and before any changes in therapeutics based on hemoglogin levels are considered in the care of patients with osteoarthritis.