Geissler 1979.

Methods	Study design: parallel RCT Recruitment: MI patients surviving the first phase of rehabilitation (in‐hospital treatment) in one East German district; June 1973‐June 1975 Allocation: not reported Blinding: not reported Randomisation: cluster‐randomisation according to hospital region Follow‐up(s): 6 months, 12 months, 2 years Description: combined rehabilitation with an inpatient and outpatient phase
Participants	Baseline characteristics Intervention group Mean age (SD): ‐ Sex (male %): 100 Number of participants: 161 Working before CHD: 146 Control group Mean age (SD): not reported Sex (male %): 100 Number of participants: 166 Working before CHD: 148 Inclusion criteria < 70 years of age at the time of the MI Exclusion criteria ‐ Baseline imbalances: ‐ Physically demanding work (i.e. white vs. blue collar): unknown Severity of CHD: unknown
Interventions	Intervention characteristics Inpatient (Phase II) and outpatient (Phase III) rehabilitation: Phase II: inpatient rehabilitation centre Daily endurance training: 30 min on bicycle ergometer, terrain training, gymnastic exercises Up to 80%‐90% the maximal symptom‐limited workload limit (monitored with pulse frequency) RTW possibilities discussed upon completion Phase III: outpatient rehabilitation: 50 min of supervised training 2 x/week in gym or indoor swimming pool 30 min daily unsupervised training with home programme Duration of intervention: Phase II 3 months Phase III 6 months (not clearly described) Providers: phase III training supervised by physical education specialist Control group Usual care through general practitioner upon hospital discharge (i.e. after phase I)
Outcomes	Proportion at work at 6 months–12 months (medium term): 12 months Proportion at work at > 12 months to < 5 years (long term): 2 years Adverse events (cardiac deaths, reinfarctions)
Identification	Sponsorship source: no information provided Country: Former East Germany (GDR) Setting: inpatient and outpatient Possible conflicts of interest: not reported Ethics committee approval: not reported
Notes	The number of people working before MI is not explicitly reported, but RTW is reported for all men aged < 65 years. Due to the sociopolitical policies in place at the time of this study, presumed that all of the participants presented in the RTW table were working prior to their heart attack.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	The study authors write that "regional cluster randomisation" was used. No further description of the randomisation method was reported.
Allocation concealment (selection bias)	Unclear risk	No method of allocation concealment was reported.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Due to the nature of the study, blinding of participants was not possible.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No outcome assessor blinding was reported, nor is it reported how RTW was assessed.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Only 2 participants from the control group refused the 2‐year follow‐up and the participants' 2‐year survival was similar in both groups.
Selective reporting (reporting bias)	Unclear risk	Unable to determine, no study protocol available
Other bias	Unclear risk	Additional sources of bias from cluster‐RCT: Recruitment bias: low risk ‐ no recruiting after “regional” randomisation reported Baseline imbalance: high risk ‐ no baseline population characteristic within clusters reported Loss of clusters: low risk ‐ no cluster loss reported; individual losses equal (13%:15%) and reasons described Incorrect analysis: unclear risk ‐ no standard errors, P values or meta‐analysis calculated; unable to combine with other studies due to lack of cluster information Comparability with individually randomised trials: unclear risk ‐ results similar to those of individually randomised studies; however, 'herd effect' is possible if people in a region are all invited to take part in rehabilitation and RTW.