Association of anemia with mobility capacity in older adults: a Korean nationwide population-based cross-sectional study

Background Over 10% of adults aged >= 65 years have anemia, as defined by the World Health Organization (WHO). As the timed up and go (TUG) test is one of the most widely used tests of mobility, this study investigated whether anemia was associated with mobility capacity assessed using the TUG test in older adults. Methods Subjects belonging to the Korean National Health Insurance Service-National Health Screening Cohort of the National Health Information Database were reviewed. Subjects were included if they had completed the TUG test as part of the National Screening Program for Transitional Ages in Korea. An abnormal TUG test result was defined as a time of >= 10 s and anemia was defined according to the WHO criteria as a hemoglobin (Hb) concentration of < 13.0 g/dL in men and < 12.0 g/dL in women. The association between anemia and TUG test results was evaluated using four multiple logistic regression models with different levels of adjustment. Stratified analysis according to risk factors was performed. Results The 81,473 subjects included 41,063 (50.4%) women and 40,410 (49.6%) men. Mean TUG time was 8.44 +/- 3.08 s, and abnormal TUG test results were observed in 22,138 (27.2%) subjects. Mean Hb concentration was 13.72 +/- 1.41 g/dL, and 10,237 (12.6%) subjects had anemia. U-shaped associations between Hb concentration and TUG test results were observed in both sexes. Subjects with anemia were 19% more likely to have abnormal TUG test results, according to the fully adjusted model (adjusted odds ratio: 1.192, 95% confidence interval: 1.137-1.247). Similar results were observed for both sexes. Stratified analysis showed that subjects with anemia were more likely to have abnormal TUG test results regardless of risk factors. Conclusions Individuals with anemia are more likely to have abnormal TUG test results, regardless of risk factors, than individuals without anemia. U-shaped relationships between Hb concentrations and TUG test results were observed in both sexes, although the optimal Hb concentration differed between men and women.