Background
Methods
Study area
Data gathering and selection criteria
Exposure variables
Outcome variables
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Perceived sleep quality: Respondents were asked: "Do you think you get enough sleep to feel rested?", and given the following alternatives: 1) Yes, in general, 2) Yes, but not often enough, and 3) No, never or almost never. The responses were dichotomised: 1 and 2 were coded into "Good perceived sleep quality", 3 was coded into "Poor perceived sleep quality". This strict cut-off value was chosen to identify as cases only those strongly perceiving poor sleep quality.
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Everyday stress: Respondents were asked: "Do you feel stressed in your everyday life?", and given the following alternatives: 1) Yes, often, 2) Yes, sometimes, and 3) No, (almost never). The responses were dichotomised: 1 into "Stress" and 2 and 3 into "No Stress". Similarly as for the sleep quality question, this strict definition of perceived stress was set to only include those strongly perceiving stress.
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Exhaustion: The SF-36 vitality scale was used to assess exhaustion [33]. The four items (How much of the time during the past 4 weeks; 1."did you feel full of pep?", 2."did you have a lot of energy?", 3."did you feel worn out?", and 4."did you feel tired?") were answered using a 6-point scale (1. "all the time", 2. "most of the time" 3. "a good bit of the time", 4. "some of the time", 5. "a little of the time" and 6. "none of the time". The points were recoded to be in the same direction (i.e. for questions 3 and 4 the reverse order was used) and then summed. Those with a sum of ≥16 (i.e. on average the first alternative on the negative half on the recoded 6-point scale)), were coded as "Exhausted". The cut-off value was chosen based on the cut-off value used in an earlier Swedish study finding changes in diurnal salivary cortisol secretion among those identified as exhausted in this way [34].
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Mental health: The GHQ12 instrument was used to assess mental health. If three or more of the 12 items were answered on the negative half on a 4-point graded scale, this denoted poor mental health (for questions see [22]). This scoring method (0-0-1-1) is the most frequently used, and the cut-off value of 3 or more points is the most commonly chosen cut-off value [35].
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Self-rated health: Respondents were asked: "How do you feel right now, physically and psychologically, considering your health and your well-being?" and asked to record their answer on a 7-point graded scale [36]. The responses were dichotomised, with answers below 5 considered low self-rated health. This cut-off value was chosen on theoretical grounds, it was assumed that commuting would not be associated with severely reduced well-being but rather the absence of feeling perfectly well.
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Sickness absence: The respondent was asked to state how many days he or she had been absent from work during the past year due to sickness. Due to concerns that this continous variable would be sensitive to the choice of cut-off value, 0, 5 and 15 days of sickness absence were used as cut-off values in a sensitivity analysis, similar to the intervals used in the public sector in Sweden as indicators of low sickness absence [37].As expected, all outcomes were significantly inter-related (all p-values < 0.001, Pearson Correlations 0.095 - 0.480).
Confounders
Total | Active < 30 min | Car < 30 min | Car 30 - 60 min | Car > 60 min | Public > 30 min | Public 30 - 60 min | Public > 60 min | |
---|---|---|---|---|---|---|---|---|
Age1 (median years) | 45 | 46 | 45 | 45.5 | 47 | 43 | 43 | 43 |
Sex1 (% male) | 50 | 42 | 54 | 63 | 76 | 37 | 38 | 50 |
University education1
(%) | 43 | 47 | 38 | 43 | 46 | 47 | 59 | 64 |
Manual workers1 (%) | 34 | 35 | 37 | 29 | 29 | 33 | 22 | 20 |
Born abroad1 (%) | 9 | 9 | 8 | 7 | 10 | 12 | 9 | 16 |
Urban residents2 (%) | 26 | 44 | 19 | 12 | 15 | 37 | 33 | 38 |
Cohabiting2 (%) | 78 | 72 | 80 | 83 | 82 | 72 | 77 | 75 |
Living with children under 13 years2 (%) | 31 | 24 | 34 | 33 | 31 | 30 | 29 | 25 |
High psycological demands at work3 (%) | 47 | 45 | 46 | 50 | 58 | 45 | 45 | 51 |
Low control at work3
(%) | 53 | 55 | 53 | 46 | 38 | 59 | 57 | 53 |
Job strain2 (%) | 22 | 22 | 22 | 29 | 20 | 25 | 24 | 24 |
Frequently working overtime2 (%) | 25 | 24 | 26 | 28 | 37 | 19 | 21 | 27 |
Unemployed during the last three years2 (%) | 10 | 9 | 8 | 10 | 13 | 12 | 14 | 19 |
Income2 (median number of price base amounts) | 6.5 | 6.0 | 6.6 | 7.1 | 8.1 | 5.9 | 6.4 | 6.3 |
Ever having problems paying bills2 (%) | 22 | 20 | 22 | 21 | 23 | 26 | 24 | 26 |
Working hours per week3 (median) | 40 | 41 | 41 | 42 | 43 | 41 | 41 | 41 |
Statistical analysis
Poor perceived sleep quality | |||||||
---|---|---|---|---|---|---|---|
Model | Commuting mode | Commuting time (min) | Resp.1 (n) | Prev.2 (%) | OR | 95% C.I. Low | 95% C.I. High |
Unadjusted | Active | < 30 | 4376 | 11 | 1.00 | ||
Car | < 30 | 10755 | 11 | 1.09 | 0.97 | 1.22 | |
Car | 30-60 | 2280 | 13 | 1.30 | 1.12 | 1.52 | |
Car | > 60 | 449 | 10 | 0.94 | 0.68 | 1.30 | |
Public | < 30 | 1332 | 10 | 0.96 | 0.78 | 1.18 | |
Public | 30-60 | 1312 | 13 | 1.27 | 1.05 | 1.53 | |
Public | > 60 | 584 | 15 | 1.55 | 1.21 | 1.97 | |
Partly adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.09 | 0.97 | 1.22 | |||
Car | 30-60 | 1.37 | 1.17 | 1.61 | |||
Car | > 60 | 1.05 | 0.76 | 1.46 | |||
Public | < 30 | 0.91 | 0.74 | 1.11 | |||
Public | 30-60 | 1.24 | 1.03 | 1.50 | |||
Public | > 60 | 1.53 | 1.19 | 1.96 | |||
Fully adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.05 | 0.93 | 1.19 | |||
Car | 30-60 | 1.37 | 1.16 | 1.62 | |||
Car | > 60 | 1.02 | 0.72 | 1.45 | |||
Public | < 30 | 0.85 | 0.69 | 1.05 | |||
Public | 30-60 | 1.17 | 0.95 | 1.43 | |||
Public | > 60 | 1.41 | 1.08 | 1.85 |
Everyday stress | |||||||
---|---|---|---|---|---|---|---|
Model | Commuting mode | Commuting time (min) | Resp.1 (n) | Prev.2 (%) | OR | 95% C.I. Low | 95% C.I. High |
Unadjusted | Active | < 30 | 4376 | 17 | 1.00 | ||
Car | < 30 | 10755 | 17 | 1.04 | 0.95 | 1.14 | |
Car | 30-60 | 2280 | 18 | 1.11 | 0.97 | 1.26 | |
Car | > 60 | 449 | 16 | 0.98 | 0.75 | 1.27 | |
Public | < 30 | 1332 | 15 | 0.90 | 0.76 | 1.06 | |
Public | 30-60 | 1312 | 20 | 1.24 | 1.06 | 1.45 | |
Public | > 60 | 584 | 20 | 1.25 | 1.00 | 1.55 | |
Partly adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.10 | 1.00 | 1.22 | |||
Car | 30-60 | 1.25 | 1.10 | 1.43 | |||
Car | > 60 | 1.21 | 0.93 | 1.58 | |||
Public | < 30 | 0.84 | 0.71 | 0.99 | |||
Public | 30-60 | 1.18 | 1.00 | 1.38 | |||
Public | > 60 | 1.23 | 0.98 | 1.53 | |||
Fully adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.11 | 1.00 | 1.24 | |||
Car | 30-60 | 1.28 | 1.10 | 1.49 | |||
Car | > 60 | 1.11 | 0.83 | 1.49 | |||
Public | < 30 | 0.81 | 0.67 | 0.98 | |||
Public | 30-60 | 1.19 | 1.00 | 1.42 | |||
Public | > 60 | 1.19 | 0.93 | 1.53 |
Low mental health | |||||||
---|---|---|---|---|---|---|---|
Model | Commuting mode | Commuting time (min) | Resp.1 (n) | Prev.2 (%) | OR | 95% C.I. Low | 95% C.I. High |
Unadjusted | Active | < 30 | 4376 | 14 | 1.00 | ||
Car | < 30 | 10755 | 13 | 0.93 | 0.84 | 1.03 | |
Car | 30-60 | 2280 | 13 | 0.91 | 0.78 | 1.06 | |
Car | > 60 | 449 | 12 | 0.88 | 0.65 | 1.18 | |
Public | < 30 | 1332 | 15 | 1.12 | 0.94 | 1.33 | |
Public | 30-60 | 1312 | 15 | 1.08 | 0.91 | 1.29 | |
Public | > 60 | 584 | 18 | 1.36 | 1.08 | 1.72 | |
Partly adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 0.98 | 0.88 | 1.08 | |||
Car | 30-60 | 1.00 | 0.86 | 1.17 | |||
Car | > 60 | 1.04 | 0.77 | 1.41 | |||
Public | < 30 | 1.04 | 0.87 | 1.24 | |||
Public | 30-60 | 1.00 | 0.83 | 1.19 | |||
Public | > 60 | 1.27 | 1.01 | 1.61 | |||
Fully adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.00 | 0.90 | 1.13 | |||
Car | 30-60 | 1.01 | 0.86 | 1.20 | |||
Car | > 60 | 0.98 | 0.70 | 1.36 | |||
Public | < 30 | 0.96 | 0.79 | 1.15 | |||
Public | 30-60 | 0.95 | 0.78 | 1.15 | |||
Public | > 60 | 1.21 | 0.94 | 1.56 |
Low self-rated health | |||||||
---|---|---|---|---|---|---|---|
Model | Commuting mode | Commuting time (min) | Resp.1 (n) | Prev.2 (%) | OR | 95% C.I. Low | 95% C.I. High |
Unadjusted | Active | < 30 | 4376 | 21 | 1.00 | ||
Car | < 30 | 10755 | 22 | 1.06 | 0.97 | 1.15 | |
Car | 30-60 | 2280 | 23 | 1.08 | 0.95 | 1.22 | |
Car | > 60 | 449 | 22 | 1.04 | 0.82 | 1.31 | |
Public | < 30 | 1332 | 24 | 1.13 | 0.98 | 1.31 | |
Public | 30-60 | 1312 | 23 | 1.07 | 0.92 | 1.24 | |
Public | > 60 | 584 | 27 | 1.35 | 1.10 | 1.64 | |
Partly adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.08 | 0.99 | 1.17 | |||
Car | 30-60 | 1.19 | 1.05 | 1.34 | |||
Car | > 60 | 1.22 | 0.96 | 1.55 | |||
Public | < 30 | 1.09 | 0.94 | 1.27 | |||
Public | 30-60 | 1.10 | 0.94 | 1.28 | |||
Public | > 60 | 1.48 | 1.20 | 1.81 | |||
Fully adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.12 | 1.02 | 1.23 | |||
Car | 30-60 | 1.25 | 1.09 | 1.43 | |||
Car | > 60 | 1.20 | 0.92 | 1.56 | |||
Public | < 30 | 1.05 | 0.89 | 1.23 | |||
Public | 30-60 | 1.06 | 0.91 | 1.25 | |||
Public | > 60 | 1.44 | 1.16 | 1.80 |
Low vitaliy | |||||||
---|---|---|---|---|---|---|---|
Model | Commuting mode | Commuting time (min) | Resp.1 (n) | Prev.2 (%) | OR | 95% C.I. Low | 95% C.I. High |
Unadjusted | Active | < 30 | 4376 | 9 | 1.00 | ||
Car | < 30 | 10755 | 11 | 1.15 | 1.02 | 1.29 | |
Car | 30-60 | 2280 | 11 | 1.16 | 0.98 | 1.37 | |
Car | > 60 | 449 | 9 | 0.91 | 0.65 | 1.28 | |
Public | < 30 | 1332 | 11 | 1.18 | 0.97 | 1.44 | |
Public | 30-60 | 1312 | 12 | 1.27 | 1.04 | 1.55 | |
Public | > 60 | 584 | 13 | 1.47 | 1.13 | 1.91 | |
Partly adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.21 | 1.07 | 1.36 | |||
Car | 30-60 | 1.38 | 1.17 | 1.64 | |||
Car | > 60 | 1.19 | 0.84 | 1.69 | |||
Public | < 30 | 1.11 | 0.91 | 1.36 | |||
Public | 30-60 | 1.34 | 1.10 | 1.64 | |||
Public | > 60 | 1.64 | 1.26 | 2.14 | |||
Fully adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.22 | 1.07 | 1.39 | |||
Car | 30-60 | 1.42 | 1.18 | 1.71 | |||
Car | > 60 | 1.26 | 0.87 | 1.82 | |||
Public | < 30 | 1.05 | 0.85 | 1.30 | |||
Public | 30-60 | 1.30 | 1.05 | 1.61 | |||
Public | > 60 | 1.55 | 1.17 | 2.07 |
Sickness absence > 5 days | |||||||
---|---|---|---|---|---|---|---|
Model | Commuting mode | Commuting time (min) | Resp.1 (n) | Prev.2 (%) | OR | 95% C.I. Low | 95% C.I. High |
Unadjusted | Active | < 30 | 4376 | 17 | 1.00 | ||
Car | < 30 | 10755 | 17 | 1.06 | 0.96 | 1.16 | |
Car | 30-60 | 2280 | 17 | 1.03 | 0.90 | 1.18 | |
Car | > 60 | 449 | 13 | 0.75 | 0.56 | 1.00 | |
Public | < 30 | 1332 | 20 | 1.23 | 1.05 | 1.44 | |
Public | 30-60 | 1312 | 19 | 1.15 | 0.98 | 1.34 | |
Public | > 60 | 584 | 16 | 0.94 | 0.74 | 1.19 | |
Partly adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.11 | 1.00 | 1.22 | |||
Car | 30-60 | 1.20 | 1.04 | 1.38 | |||
Car | > 60 | 0.94 | 0.70 | 1.26 | |||
Public | < 30 | 1.20 | 1.03 | 1.42 | |||
Public | 30-60 | 1.23 | 1.05 | 1.45 | |||
Public | > 60 | 1.08 | 0.84 | 1.37 | |||
Fully adjusted | Active | < 30 | 1.00 | ||||
Car | < 30 | 1.15 | 1.04 | 1.27 | |||
Car | 30-60 | 1.27 | 1.10 | 1.47 | |||
Car | > 60 | 1.03 | 0.75 | 1.41 | |||
Public | < 30 | 1.14 | 0.97 | 1.35 | |||
Public | 30-60 | 1.16 | 0.98 | 1.38 | |||
Public | > 60 | 0.96 | 0.74 | 1.25 |