Table 3 Definitions of controlled variables and description of the mean

Gender

Dummy variable: male = 1, female = 0

1 = 60.75%, 0 = 39.25%

Age

Continuous variable: age of the participant

Mean = 66.2507

Ethnic

Dummy variable: Han ethnicity = 1, ethnic minorities = 0

1 = 90.86%, 0 = 9.14%

Type of Household Registration (Hukou)

Rural

Dummy variable: rural hukou = 1, others = 0

1 = 60.10%

Nonrural hukou

Dummy variable: nonrural hukou = 1, others = 0

1 = 38.05%

Rural to resident hukou

Dummy variable: rural to resident hukou = 1, others = 0

1 = 1.23%

Nonrural to resident hukou

Dummy variable: nonrural to resident hukou = 1, others = 0

1 = 0.62%

Marital Status

Single

Dummy variable: single = 1, others = 0

1 = 0.91%

Married

Dummy variable: married = 1, others = 0

1 = 80.62%

Divorce or widowed

Dummy variable: divorced/widowed = 1, others = 0

1 = 18.47%

Education level

Categorical variable: unschooled = 1, primary school = 2, middle school = 3, high school or technical secondary school = 4, postsecondary college = 5, university = 6, postgraduate = 7

1 = 13.38%, 2 = 38.72%, 3 = 29.86%, 4 = 12.11%, 5 = 3.84%, 6 = 2.07%, 7 = 0.02%。

Range of Migration

Interprovince

Dummy variable: participant migrated from one province to another = 1, otherwise = 0

1 = 42.04%

Intercity

Dummy variable: participant migrated from one city to another within the same province = 1, otherwise = 0

1 = 31.47%

Intercounty

Dummy variable: participant migrated from one county to another within the same province = 1, otherwise = 0

1 = 26.49%

Monthly household income

Continuous variable: monthly household income of the participant (after tax)

Mean = 4975.873

Main Source of Income

Employment

Dummy variable: participant’s main source of income is his/her own employment = 1, otherwise = 0

1 = 30.73%

Pension/Savings

Dummy variable: participant’s main source of income is pension or savings = 1, otherwise = 0

1 = 42.22%

Other family members

Dummy variable: participant’s main source of income is from other family members = 1, otherwise = 0

1 = 22.48%

Others

Dummy variable: participant’s main source of income is from none of the three aforementioned categories = 1, otherwise = 0

1 = 4.57%

No. of friends at place of residence

Continuous variable: no. of friends at place of residence

Mean = 8.4683

Daily exercise time (min)

Continuous variable: average time spent exercising daily, in minutes

Mean = 66.0203

Physical examination

Dummy variable: participant has had at least one physical examination in the past year = 1, otherwise = 0

1 = 35.62%, 0 = 64.38%

Self-rated health

Categorical variable: very unhealthy = 1, unhealthy = 2, basic health values = 3, health values = 4

1 = 0.91%, 2 = 8.70%, 3 = 44.45%, 4 = 45.94%