# Table 2 Explanatory variables sorted into six blocks.

Original variables New variables
Background Gender
1 = women, 0 = men

Length: cm
Weight: kg
Body mass index (BMI) = weight/length2
Overweight:
1 = BMI>25, 0 = BMI ≤ 25
Lifestyle "How many times PER WEEK do you have breakfast?"
0 time, 1 time, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times
Breakfast regularly:
1 = >5 days/week, 0 = ≤ 5 days/week
Smoking:
"Have you been smoking daily or almost daily during the LAST 7 DAYS?"
1 = yes, 0 = no

"Have you been using snuff daily or almost daily during the LAST 7 DAYS?"
yes, no
Snuff use:
1 = uses snuff and does not smoke
0 = does not use snuff, or uses snuff but also smokes
Physical activity:
"Approximately how much time have you spent time on the following activity during the LAST 7 DAYS?: Exercise, training"
h/week

Demands "What do you think of the demands of work/study performance in your work/study situation?"
Demands of work/studies are absolutely too high-Agree totally, Demands of work/studies are absolutely too high-Agree partially, Demands are neither to high nor to low, Demands of work/studies are absolutely too low-Agree partially, Demands of work/studies are absolutely too low-Agree totally
"Do the demands at work/studies affect your home and family life negatively?"
Very rarely, rarely, some times, often, very often
High work/study demands:
0 = Demands of work/studies are not
too high
1 = Demands of work/studies are too high, but do not affect home life
2 = Demands of work/studies are too high and affect home life
High home life demands:
Very rarely, rarely, some times, often, very often

"Approximately how much time have you done the following activity during the LAST 7 DAYS?"
Schoolwork (scheduled)
Schoolwork (unscheduled)
Gainful employment/paid work/practical training
h/week
Work/study time: Sum of scheduled and unscheduled studies and paid work
h/week
Psychosocial factors "Take position to the following statement about your school/workplace: I get a long with superiors or teachers."
Exactly right, about right, not especially right, not right at all
Good superiors:
1 = Exactly right, about right
0 = Not especially right, not right at all
"Take position to the following statement about your school/workplace: I get a long with colleagues or fellow students."
Exactly right, about right, not especially right, not right at all
Good colleagues:
1 = Exactly right, about right
0 = Not especially right, not right at all
Ergonomics
Computer use pattern
"Do you use/have you been using the following equipment?"
Ordinary desktop computer (PC)
Laptop computer
Yes
Time using PC: h/week
Not included due to multicollinearity with No pause.
"How many times during the LAST 7 DAYS have you been using the following equipment for more than 4 hours without a break (pause for more than 10 min)?"
Personal computer
0 time, 1 time, 2–4 times, 5 or more times
Computer use pattern:
0 = 0 time during last week
1 = 1 time during last week
2 = 2 or more times during last week
Health Asthma: "Have you received the diagnose asthma from a physician?"
1 = asthma diagnosed by physician, 0 = otherwise

Perceived stress: "STRESS refers to a state when one feels tens, restless or worried or not being able to sleep at night because one thinks of problems all the time.
Have you experienced this kind of stress for a period lasting longer than 7 days, during the LAST 12 MONTHS?"
1 = yes, 0 = no

1. Variables written in bold style are variables later used in the regression analysis.