Table 1.

Description of variables and measurements of the 6-year longitudinal health survey data in Huainan

Variable Names	Code for this study	Measurement in the dataset
Socio-demographic
Age groups	0 = 55–59, 1 = 60–64, 2 = 65–69, 3 = 70–74, 4 = 75–79, 5 = 80–84, 6 = 85–89, 7 = 90–94 8 = 95–99 years	Same
Gender	0 = male, 1 = female	Same
Educational level	0 = none-to-primary school, 1 = middle school, 2 = high school, and 3 = college	Same
Self-rated income	0 = none-or-low income, 1 = high income	Same
Physical Activity
Levels	0 = no PA; 1 = irregular PA (not included in IPAQ categories); 2 = low PA (PA practice less than 599 MET-min/week); and 3 = moderate PA (PA practice between 600 and 3000 MET-min/week)a	By frequency and lengthb.

^a The calculation of the metabolic equivalent (MET) minute of PA per week, based on which the annual repeated PA were categorized into four levels according to the International Physical Activity Questionnaire

^b Frequency: 0 = no activity, 1 = irregular activity, 2 = regular activity less than three times a week. Length: 0 = no activity; 1 = less than 20 min; 2 = 20 to 60 min; 3 = 60 min or greater