Insomnia is Associated with the Effect of Inpatient Multimodal Occupational Rehabilitation on Work Participation in Workers with Musculoskeletal or Mental Health Disorders: Secondary Analyses of a Randomized Clinical Trial

Figures & data

Table 1 Characteristics of the Study Population Stratified by Occupational Program and Insomnia

	Occupational Rehabilitation Program
	Inpatient (n=86)		Outpatient (n=77)
	Insomnia^a	No Insomnia	Insomnia^a	No Insomnia
Participants, % (n)	56 (48)	44 (38)	56 (43)	44 (34)
Age, mean (SD)	46.2 (9.1)	46.3 (8.3)	46.9 (10.2)	43.0 (10.3)
Women % (n)	85 (41)	76 (24)	63 (27)	91 (31)
Higher education % (n)^b	33 (16)	42 (16)	40 (17)	50 (17)
Main diagnoses for sick-leave (ICPC-2) % (n)^c
L- musculoskeletal	58 (28)	68 (26)	49 (21)	53 (18)
P- psychological^d	42 (20)	32 (12)	51 (22)	47 (16)
Number of days with sick leave at inclusion, median days (IQR)^e	200 (165–263)	211 (161–273)	202 (172–287)	219 (190–244)
Average pain (0–10), mean (SD)^f	5.5 (2.0)	4.2 (1.8)	4.9 (2.4)	4.7 (1.9)
HADS, mean (SD)
Anxiety (0–21)	8.8 (4.0)	5.6 (2.9)	10.0 (3.8)	6.7 (3.6)
Depression (0–21)	6.6 (4.6)	4.6 (3.3)	7.9 (3.7)	4.5 (3.6)
Insomnia severity index (0–28), mean (SD)	16.6 (4.1)	5.2 (3.5)	16.8 (3.3)	5.7 (3.0)

Notes: ^aInsomnia defined as an Insomnia Severity Index score ≥11. ^bCollege or university. ^cBased on data in the medical certificate from the National Social Security System Registry. ^dThese include 13 participants with fatigue and one with perinatal distress. ^eNumber of days on sick leave during the last 12 months prior to inclusion. Measured as calendar days, not adjusted for graded sick-leave or part time job. ^fAverage pain last week.

Abbreviation: HADS, Hospital Anxiety and Depression scale.

Figure 1 Flowchart of the participants in the study. ^aNot eligible: Participating in another treatment program (n=22), serious somatic/psychiatric illness (n=11), specialized treatment needs (n=4), problems with functioning in groups (n=3), surgery scheduled next 6 months (n=2), insufficient language skills (n=2), alcohol/drug abuse (n=1), no longer on sick-leave (n=10), medical assessment not completed (n=15), not motivated (n=6), inability to participate in an inpatient intervention (n=7). ^bOther reason: unknown (n=4).

Table 2 Associations of Occupational Program and Insomnia with Accumulated Sick Leave During 12 Months Follow-Up. Insomnia Measured by Insomnia Severity Index (ISI)

	No. of Persons	Days with Sick Leave
		Age Adjusted Mean	Age-Adjusted Mean Difference (95% CI)^a	Multi-Adjusted Mean Difference (95% CI)^ab
No insomnia^c
Inpatient program	38	105	Reference	Reference
Outpatient program	34	105	0 (−40 to 39)	−3 (−43 to 37)
Insomnia^d
Inpatient program	48	97	−8 (−44 to 28)	−12 (−48 to 24)
Outpatient program	43	148	43 (5 to 80)	46 (8 to 83)

Notes: ^aMean difference: difference in number of sick leave days relative to the reference group of people in the inpatient program without insomnia. ^bAdjusted for age, sex and education. ^cISI-score <11. ^dISI-score ≥11.

Abbreviations: CI, confidence interval; ISI, Insomnia Severity Index.

Figure 2 Sick leave days (cumulative mean) during 12 months of follow-up for participants in each stratum of occupational programme and insomnia.