Identification and eligibility of study participants
The study will be performed in several OH units of medium sized and large private or public enterprises, in which the employees are known to be exposed to physically strenuous or static work tasks (Figure ). Employees who seek medical advice primarily due to musculoskeletal pain in the neck or shoulder region, back, or upper or lower extremities are eligible to the study. The symptoms and related disability must warrant prescription of full-time sick leave according to the current practice, but the physician considers the employee to be able to work part-time without the risk of the health condition to deteriorate. Table shows the inclusion and exclusion criteria.
Eligibility of the participants
During the initial visit, the OH physician will inform the employee about the study and its aims. If the employee agrees to participate, informed consent will be signed. It includes a permission to contact the supervisor, preferably during the same visit, in order to verify whether the work-related arrangements for part-time sick leave are feasible, in case the employee is allocated to the intervention group. If the supervisor disagrees, the employee will be excluded from the trial.
Once the agreements from the employee and the supervisor have been obtained and before the randomisation has occurred, the physician will determine the length of the sickness absence based on symptoms (Table ), clinical findings [12
] and background information (Table ). If the employee is allocated to part-time sick leave (intervention group), daily work load will be reduced by restricting work time. Also, if necessary, remaining work tasks will be modified so that working should be possible despite the symptoms. In the control group, work load will be eliminated with full-time sick leave. Both groups will receive appropriate medical advice, and the need for medical treatments and a control visit will be determined as usual.
Health-related variables inquired at baseline and during follow-up
Explanatory variables measured at baseline
In the following day after the initial visit, those allocated to part-time sick leave will return to work for 40 to 60% of their regular working hours. They are asked to give their supervisor a statement from the physician indicating the duration of part-time sick leave, what kind of work loads are allowed and which are not recommended, and if any additional work adjustments are needed. If the reduction of work time cannot be organised on a daily basis, the employee may work every second day for the whole day and every second day stay at home.
When the sick leave is over, employees in both groups return to regular work. Those who are unable to resume regular work activities will be re-evaluated by an OH physician, who can prescribe either full-time sick leave or continue part-time sick leave, according to the physician's clinical judgement. The length of sick leave will be determined as usual.
If the employee in the part-time sick leave group needs full-time sick leave, part-time sick leave cannot be applied again after full-time sick leave has ended. Return to part-time sick leave is possible in a situation when the health problem relapses within one month after the employee has returned to regular work. The total maximum length of the part-time sick leave is two months. Participation in the study intervention does not affect the employee's right to general social security benefits. Neither does it have any financial effect to the employee, because he or she receives the same compensation (regular salary) during part-time and full-time sick leave. The employer will start receiving compensation after the sick leave has lasted for 10 working days.
Musculoskeletal symptoms typically deteriorate during the work day and towards the end of the work week, and they resolve during break, night rest and weekend [14
]. Our hypothesis to be tested in the current study is that employees whose work time is temporarily reduced and work load adjusted during early stage of disability will have less disability days and faster return to regular work duties than employees on conventional sick leave.
The main outcomes are the number of days from the initial visit to the return to regular work activities and the total number of part- and full-time sick leave days during one- and two-year follow-up. Other outcomes are changes in symptoms as well as in self-assessed functioning during follow-up [15
Data on self-assessed workload will be collected after the initial visit and during part-time sick leave in order to recognise physically strenuous work tasks relevant to MSDs [18
], as well as to list the work adjustments made during the part-time sick leave. This will be included in an internet based questionnaire together with the symptoms and background variables [20
]. The questionnaire will be sent to the employees immediately after recruitment and at one, three, eight, 12 and 52 weeks. Those without access to internet will be telephone-interviewed by a researcher. Also, the supervisors in both groups will be interviewed by phone after the employee has returned to work.
Participating employees, their supervisors, OH personnel, human resources management, as well as occupational safety and trade union representatives will be interviewed, and the feasibility of early part-time sick leave will be evaluated based on the qualitative information collected in the interviews. From those employees, who decline to participate, only information on age and gender will be collected. They will also be offered a possibility to provide the main reason for not participating. This can be done with an anonymous questionnaire that can be returned in a closed envelope directly to the researchers. The reason for a negative response from the supervisor is also documented.
The follow-up is extended to two years with the purpose of detecting the possible longer-lasting effects on e.g. illness behaviour. One and two years after the initial visit, the dates and diagnoses of all sickness absences (including those prescribed outside OH services) will be collected from the OH units.
Patient enrolment started in January 2008 and it is planned to last until July 2009. Follow-up of the last participants will finish two years later in 2011. Based on the pilot study, however, preliminary results on the feasibility of early part-time sick leave will be available already in 2008.
Costs and benefits to the employee, employer and society will be estimated in both study groups. Costs due to lost working time will be analysed separately taking into account the compensation to the employer during full- or part-time sick leave. Data on costs of the used health services, medications, and medical aids (due to the main health problem) will also be collected. In addition, the analysis will include the compensation of the lost work input using stand-ins (salary, training time) or overtime (performed by the colleagues of the study subjects), as well as the time the supervisor used for work arrangements.
The non-monetary benefits will be studied based on self-assessed productivity at work [26
], as well as the reduction of pain and disability measured on a scale from 0 to 10 (Table ). If there is a difference between the groups in the outcome measurements, a cost effectiveness analysis will be performed dividing the costs by the units of difference in the outcome. If there is no significant difference between the study groups in any of the health related outcomes, the analysis of total costs in both groups will be applied in making the final conclusions.
A 10% difference between intervention and control group in the proportions of employees returning to regular work at a given time point will be considered significant. The power of the study is aimed at 80%, and the level of significance at 0.05. Assuming a drop-out rate of 10–15%, 600 employees will be needed for the study (300 in both groups). Using previous information on sickness absenteeism in Finnish enterprises, and to ensure a sufficient pool of subjects, we will include in the study base a sufficient number of companies employing up to 30 000 persons.
Employees will be randomised using sealed opaque envelopes, which contain information on the allocated group. The allocation has been performed at the Finnish Institute of Occupational Health using a random number generator and block randomisation in order to obtain equal size of intervention and control group for the participating physicians.
Due to practical and ethical reasons neither the employee nor the physician will be blinded to group assignment during the initial visit. Allocation is also open to the two interviewers and to the other possible physicians during later visits.
A survival analysis will be used to study the time to return to work in the intervention and control group. The amount of sick leave days will be analysed at 12 and 24 months, and the associations between the outcomes and background variables will be analysed using general linear models. In addition, the change in symptoms and disability indices will be studied at various time points using general linear models for repeated measurements.
Subgroup analyses will be performed in relation to patient compliance, type of work, adequacy of work adjustments, previous sick leaves, pain characteristics (such as localisation, duration), and level of disability at baseline. All analyses will be made based on an intention-to-treat principle.
The Coordinating Ethics Committee of Hospital District of Helsinki and Uusimaa has granted approval for this study.
Clinical Trial Register
This study has been registered at International Standard Randomised Controlled Trial Number Register, register number ISRCTN30911719