Table 4 Variables assignment

DOAHPS^a

 < 43 points = 0, ≥ 43 points = 1

Age

65 ≤ Age < 70 = 1, 70 ≤ Age < 75 = 2, 75 ≤ Age < 80 = 3, 80 ≤ Age < 85 = 4, Age >  = 85 = 5

Sex

Male = 0, Female = 1

Residence

Rural = 0, Urban = 1

Education level

Illiteracy = 1, Primary school = 2, Junior high school = 3, High School/Technical School = 4, College degree and above = 5

Pre-retirement occupation

Government staffs = 1, Industry and service workers = 2, Agricultural sector or others = 3

Medical insurance

Basic Medical Insurance for Urban Employees = 1, Basic Medical Insurance for Residents = 2, Others = 3