“…In terms of the average age of the research subjects, 2 studies targeted subjects in their 40s or below [16,22]; 6 studies targeted subjects in their 50s [5,28e31,38]; 5 studies targeted subjects in their 60s [11,24,25,35,36]; 4 studies targeted subjects in their 70s or older [23,27,32,37], and 4 studies targeted subjects with an unclear average age [21,26,33,34]. Large studies that targeted 100 or more subjects were 13 (61.9%) [5,16,21,25,26,29,30,32e36,38], and 6 studies targeting more than 300 subjects [21,26,30,35,36,38].…”