Measurement

During health screening, the self-administered questionnaires were used to collect the demographic data, medical history, socioeconomic history including smoking status and alcohol intake, educational background, and level of PA. Alcohol intakes of > 30 g/day for men and > 20 g/day for women were defined as high alcohol intake^41,42; higher education was defined as college graduate or a higher level of education. The National Health Interview Survey criteria were used to define the smoking status. Current smokers were defined as those who smoked more than 5 packs (more than 100 cigarettes) in their lifetime and currently smoking at the time of the interview. A former smoker was defined as a person who had smoked more than 100 cigarettes in their lifetime but who had quit smoking at the time of the interview⁴³.

The self-administered form of the Korean version of the International Physical Activity Questionnaire (IPAQ) was used to validate the PA levels³⁸. In the questionnaire, participants were instructed to record the frequency and duration of PA over the past 7 days. All participants indicated the frequency (0–7 days/week) of every moderate or vigorous PA performed. PAs that lasted more than 10 min were included in the count. The duration of PA was recorded on a daily basis (min/day). In the same way, the time that the participants performed walking and other physical movements, including transportation, house chores, and working and leisure activities, were recorded (0–7 days/week and minutes/day). The total physical inactivity time was assessed using the following question: “During the last 7 days, how much time did you spend sitting or lying per each day?” Physical inactivity was defined as all activities performed while sitting or lying down. Strength exercises such as push-ups were counted separately based on the number of times per week. The participants were classified into three categories: sedentary, mild PA (600 metabolic equivalent of task [MET]-minutes per week), and health-enhancing PA (3,000 MET-minutes per week)³⁸.

Anthropometric measurements (height, weight, systolic blood pressure, and diastolic blood pressure) were performed by trained medical staff. During the measurements, the participants wore a lightweight hospital gown (< 0.1 kg) without shoes. Body mass index (BMI) was calculated as weight divided by height in meters squared (kg/m²). Blood pressure (BP) was measured after a period of rest in a sitting position. During the BP measurement, the arm was positioned at the heart level, and an automated oscillometric device (53,000, Welch Allyn, New York, USA) was used. Blood biochemical samples were collected after fasting for > 10 h. The blood samples were analyzed by the Laboratory Medicine Department at Kangbuk Samsung Hospital, which has been accredited by the Korean Association of Quality Assurance for Clinical Laboratories and the Korean Society of Laboratory Medicine.