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Changes in the number of (A) male and (B) female participants from 2001 to 2015. Not-old, subjects <65 years of age; young-old, subjects aged between 65 and <70 years; old-old, subjects aged ≥75 years. The ratio of elderly subjects to all participants increased for both male and female subjects over the 15 years of the study (P < .001, Chi-squared test).
