Table 1 Description of variables

Difficulty in physical functioning (of year 2018)

In year 2018, the mean score of the following items. “Do you have any difficulty with running or jogging about 1 km?”, “Do you have difficulty with getting up from a chair after sitting for a long period?”, “Do you have difficulty with climbing several flights of stairs without resting?”, “Do you have difficulty with stooping, kneeling, or crouching?”, “Do you have difficulty with reaching or extending your arms above shoulder level? (he/she is regarded as not having difficulty only if he/she can extend both of his/her arms, otherwise he/she is regarded as having difficulty.)”, “Do you have difficulty with lifting or carrying weights over 10 jin, like a heavy bag of groceries?”, “Do you have difficulty with picking up a small coin from a table?”. (=1, No, I don’t have any difficulty... =4, I cannot do it).

Problems of cognitive status (of year 2018)

In year 2018, the mean score of the following items. “how well at recognizing the face of family members and friends?”, “how well at recognizing the name of family members and friends?”, “how well at remembering things about family and friends, such as occupations, birthdays, and addresses?”, “how well at remembering things that have happened recently?”, “how well at recalling conversations a few days later?”, “how is at forgetting what was about to say in the middle of conversations?”, “how is at remembering [his/her] address and telephone number?”, “how is at remembering what day and month it is?”, “how is at remembering where things are usually kept?”, “how is at remembering where to find things which have been put in a different place from usual?”. (=1, much better; =2, improved; =3, not much changed; =4, gotten worse; =5, much worse).

Late retirement status of 2015

In year 2015, the status of late retirement is coded 1, if he (or she) reports the status of working in the most recent year and he (or she) is aged > 60 (or > 55); And the status of late retirement is coded as 0, if he (or she) reports the status of not working in the most recent year and he (or she) is aged > 60 (or > 55). The cut-off point is gender-specific and according to the regulation of legal retirement age in China.

Social behavior

=1, if he/she has one of the following social behavior; =0, otherwise. “Interacted with friends”, “Played Ma-jong, played chess, played cards, or went to community club”, “Provided help to family, friends, or neighbors who do not live with you”, “Went to a sport, social, or other kind of club”, “Took part in a community-related organization”, “Done voluntary or charity work”, “Cared for a sick or disabled adult who does not live with you”, “Attended an educational or training course”, “Stock investment”, “Used the Internet”.

Insurance

=1, if he/she has at least one of the following health insurances, including Urban Employee Basic Medical Insurance (UEBMI), Urban Resident Basic Medical Insurance (URBMI), and New cooperative medical scheme (NCMS); =0, otherwise.

Gender

=1, Male; =2, Female.

Age

The age of respondents.

Education

=1, less than lower secondary; =2, upper secondary & vocational training; =3, tertiary.

Marriage

Indicator (0–1 binary) variable of the following respective status: married; partnered; separated; divorced; widowed; never married.

Residence place

Indicator (0–1 binary) variable of the following respective places: central city/town; urban-rural integration zone; rural; special zone.