Table 3

Study characteristics of the high quality studies

Study	Quality score	Study population	Sex	Sample size	Participation rate (%)	Exposure shift workers	Recall/register period	Outcome measures
Prospective cohort studies
Tüchsen et al 35	67%	Danish carers of the older population: social, nursing home, home care and healthcare assistants/helpers	Female	N=5627: 1231 evening; 405 night; 748 shifts 3243 days	78.7%	Fixed evening, fixed night, rotating shifts	Register: 52 weeks	Incidence of sick leave spells of ≥2 weeks Incidence of sick leave spells of ≥8 weeks
Tüchsen et al 36	67%	Danish working population, random sample	Shift workers: 49% male Day workers: 52% male	N=5017: 1008 shift workers; 4009 days	75%	Irregular working hours	Register: 78 weeks	Proportion of sick leave spells lasting ≥2 weeks Proportion of sick leave spells lasting ≥8 weeks
Case-control studies
Kleiven et al 38	76%	Norwegian chemical plant workers	Cases: 91.8% male Referents: 91.5% male	Cases/references: N=3580/7582	NA: Data retrieved from registers	3-Shift system	Register: 10 years	Sick spells >3 days
Bourbonnais et al 39	59%	Canadian nurses with sick leave diagnosed ‘most likely to be related to work load’	Female	Cases/references: N=184/1165 Schedules: 42/240 evening; 32/154 night; 46/268 shifts, 24/162 unknown; 40/341 days	NA: Data retrieved from registers	Fixed evening, fixed night and rotating shifts	Register: 3 years 5 months	Sick spells ≥6 days for full-time workers, ≥8 days for part-time workers
Cross-sectional studies
Higashi et al 40	67%	Japanese chemical fibre and textile workers in production, maintenance and service departments	Male	N=26 324: 13 472 3-shifts; 12 852 days	NA: Data retrieved from registers	3-Shift system	Register: 1 year	% Spells/man/year % Number of lost work days/total normal potential work days
Niedhammer et al 41	62%	French workers, random sample from voluntarily participating occupational physicians	58.2% male	N=24 486: 3206 shifts excluding nights; 1111 nights; 1256 shifts including nights; 18 913 days	96.5%	Shift work without nights, fixed night, shift work including nights	Recall: 12 months	Proportion of workers who had at least 1 sick leave spell of >8 days
Böckerman and Laukkanen42	54%	Finnish workers from all sectors of the economy: mostly blue-collar workers	58% male	N=725: 297 shift/period workers, 428 not shift/ period workers	69%	Shift and period work as one group	Recall: 12 months	Proportion of workers with ≥2 sick leave days
Ohayon et al 43	54%	French psychiatric hospital staff: medical, maintenance, social services and administrative staff	2-Shift: 21.4% male; Fixed/rotating nights: 40.4% male Fixed day: 31.9% male	N=817: 323 2-shift; 52 fixed/rotating night; 442 day	40.7%	2-Shift system, fixed/rotating nights	Recall: 12 months	Proportion of workers who had at least 1 sick day
Eyal et al 44	54%	Israeli shift workers in a company: industry unknown	Male	N=519: 250 shift workers; 269 white-collar workers	NA: Data retrieved from registers	Shift work	Register: 12 months	≥20 accumulated days of registered absence