Table 1 Outcome variables, questions, and responses

Aspects of health

Perceived stress

How do you rate your general state of health?

Very good, pretty good, neither good nor poor, pretty poor, poor

Very good health: 1 = Very good health

0 = Pretty good health or less

Sleep disturbance

During the past 6 months, have you been bothered by:

Never, Once/a few times per year, Once/a few times per month, Several times/week, Every day

Sleep disturbance: Variables based on Keklund and Akerstedt’s work [28] were combined into one variable based on the mean of the four items, rescaled to a 0–10 scale, were 0 is a low level of sleep disturbance and 10 is a high level of sleep disturbance.

– difficulties falling asleep?

– repeated awakenings with difficulties going back to sleep?

– not being thoroughly rested at awakening?

– feeling tired/sleepy during studies or leisure time?

Stress (Mood)

How have you felt during studies/work in the past 7 days?

Not at all, Almost, A bit, Quite, Very, Extremely

Based on the Mood scale [29]. Low stress or energy = 1 and high stress or energy = 6.

– rested

– tense

– stressed

– relaxed

– pressured

– calm

Energy (Mood)

How have you felt during studies/work in the past 7 days?

Not at all, Almost, A bit, Quite, Very, Extremely

– active

– listless

– energetic

– ineffective

– alert

– passive

General performance

Decreased general performance

Have pain/aches in the muscles/joints affected your performance in general during the last month?

Yes, No

1 = yes

0 = no