Table 1.
Presenting baseline characteristics of the cohort with baseline stable NCP or CRP and individuals excluded from the study due to reporting CWP in − 95 and/or − 98. Prevalence of baseline exposures and covariates in included and excluded subjects, and history of CWP in excluded individuals. Significance of differences between included and excluded subjects are presented as p-values (tested with t-test and chi2-test respectively)
| Included cohort (stable NCP or CRP) (n = 1512) | Excluded subjects (CWP in 1995 and/or 1998) (n = 340) | p-value for diff. Incl. vs excl. | |
|---|---|---|---|
| Age (1998) | < 0.01 | ||
| Mean (sd) | 49 (15) | 56 (13) | |
| Gender; n (%) | <.01 | ||
| Male | 729 (48) | 111 (33) | |
| Female | 783 (52) | 229 (67) | |
| Initiating sleep; n (%) | <.01 | ||
| No Problem | 1211 (81) | 175 (53) | |
| Problem | 282 (19) | 158 (47) | |
| Maintaining sleep; n (%) | <.01 | ||
| No Problem | 1024 (69) | 109 (33) | |
| Problem | 461 (31) | 220 (67) | |
| Early awakening; n (%) | <.01 | ||
| No Problem | 1149 (78) | 145 (44) | |
| Problem | 331 (22) | 186 (56) | |
| Non restorative sleep; n (%) | <.01 | ||
| No Problem | 1075 (73) | 123 (37) | |
| Problem | 404 (27) | 207 (63) | |
| Fatiguea | <.01 | ||
| Mean (sd) | 72 (21) | 44 (25) | |
| Number of Regions | <.01 | ||
| 0 | 1096 (73) | 42 (12) | |
| 1–2 | 204 (13) | 10 (3) | |
| 3–5 | 177 (12) | 80 (24) | |
| 6–11 | 35 (2) | 152 (45) | |
| 12–18 | 0 | 56 (17) | |
| Mental Healthb | < .01 | ||
| Mean (sd) | 84 (17) | 69 (23) | |
| Socio economyc | < .01 | ||
| High non manual work | 440 (29) | 48 (14) | |
| Ass non manual | 212 (14) | 55 (16) | |
| Manual | 664 (44) | 196 (58) | |
| Others | 196 (13) | 41 (13) | |
| CWP history at baseline | |||
| CWP in −95 only | – | 103 (30) | |
| CWP in −98 only | – | 101 (30) | |
| CWP in both −95 and − 98 | – | 136 (40) | |
aAssessed by SF-36 vitality scale; bAssessed by SF-36 Mental health scale; cClassified by occupation – intermediate/higher non-manual employees, Assistant non-manual employees, Manual workers and “others”