Four-year incidence of sick leave because of neck and shoulder pain and its association with work and lifestyle
From: Spine. 2009 Feb 15;34(4):413-8
Musculoskeletal disorders are one of the important health problems in the world. With the exception of back pain, neck and shoulder pain is one of the prevalent disorders in workplaces and a common reason for abseentism, job change, and disability pension.
The incidence and prevalence of neck and shoulder pain have a broad range in different studies, depending on which data collection method is used (self-reported questionnaire, medical examination, sickness absence). Neck and shoulder pain is a dynamic entity that can change over time, but few longitudinal studies have been performed on workplace populations to address the above-mentioned issues.
The relation between neck and shoulder pain and physical as well as psychosocial factors at work have been studied and approved (with different consistency) in different surveys. Most of these studies are cross-sectional and related to high-income and industrialized countries. There is little information about neck and shoulder pain in the general population in developing and low-income countries. There are even fewer studies in working populations.
The main aim of this longitudinal investigation was to determine the incidence of sick leave because of neck and shoulder pain in a large population of Iranian workers, and to study its relation with physical and psychosocial factors at work, lifestyle, and previous pain. An additional aim was to compare risk factors for future sick leave versus risk factors for self-reported neck and shoulder pain in the cross-sectional baseline study.
Our study shows an extremely low incidence of neck and shoulder pain compared with previous studies. A limited number of longitudinal studies on the incidence of neck and shoulder pain have been conducted in high-income countries. However, to our knowledge there are no such studies from middle or low income countries. In this study, we used sickness absence because of neck and shoulder pain as our outcome.
There are several difficulties when trying to compare studies on sickness absence, since not only the study design but also outcome measures, terminology, and insurance systems (among nations as well as over time) differ widely.
In the literature, there are different views on the importance of self-reported symptoms. One view emphasizes the progression of these disorders from development of symptoms, followed by reporting symptoms and seeking health care, and then finally the need for sick leave and resulting disability. Health outcomes such as symptoms, care-seeking, and sick leave overlap, but give different windows of the magnitude of the problem. In addition to the severity of a disorder, care-seeking is probably influenced by family situation and occupation, as well as activities during leisure time and in society.
IKCo has a young population of employees; the average age at baseline in 2003 was 29.6 years. All employees undergo a pre-employment medical examination and there are some restrictions regarding the employment of people with certain diseases. Our study population is a young selected group of probably very healthy workers, which of course, might influence the incidence of sick leave. Job insecurity could be another important factor. Iran is a country with a high rate of unemployment and people are very keen to keep their jobs, which might also affect the incidence of sick leave.
According to insurance legislation in Iran, sickness benefit is payable in cases of disease, or injuries, that reduce work capacity. For 3 days or less, a general medical certificate (from within or outside the insurance system) may be accepted by the company or any other insurance system. In cases of sickness absence lasting more than 3 days, medical certificates must be confirmed by physicians who are approved by the insurance system. For long-term sickness absence (>60 days), sickness benefit is payable based on a confirmation of diagnosis by the expert medical board at the insurance organization. Sickness benefit is payable by the insurance organization from the first day of accident and the fourth day of disease. The insurance system pays 70% of the salary but it does not include overtime. Most workers in industries have overtime and they are dependent on this part of the salary.
In Iran, there is no time limit for sickness benefit payment, and it will continue as long as the insurance organization expert committee approves it. In severe cases where employees have partially or completely lost their work ability, this committee will give them partial or complete disability pension. There is no part-time sickness absence and benefit in Iran.
Low incidence and high prevalence give rise to the theory that maybe most workers continue to work regardless of pain and disability. Such behavior has been reported from different countries, among both sexes, and for various illnesses. Working when ill referred to as presenteeism or sickness attendance has been reported for LBP and neck and shoulder pain. Studies show that presenteeism is most common among professionals, e.g., physicians and nurses, whose work ethic of commitment and responsibility to serve others may be considered more important than their own needs. Sickness presenteeism has also been observed in organizations where the absent employee cannot be easily replaced; thus sick leave causes negative consequences for the absentee, workmates or a third party. Financial loss, accumulated work tasks and job security could also be main reasons. A study by Hansson et al shows that reporting sick is neither undertaken lightly nor for short-term reasons only. Instead, personal history and anticipated spine-related pain in the future, as well as workplace and labor market factors, are also important considerations.
Although most studies show that recurrence of neck and shoulder pain is common, our study only has 6 cases with more than 1 episode of neck and shoulder pain during the 4-year follow-up. One possible explanation for this contradictory result might be that most employees in our cohort continue doing their job despite having pain.
We have no information about the care-seeking behavior of employees who suffer pain but are not sick-listed. Such information could perhaps help to increase our knowledge of health behavior and reasons for sick-listing.
The low incidence of neck and shoulder pain becomes more complex when we compare it with incidence of low back pain in the same cohort. Although the prevalence of neck/shoulder and back pain were similar at baseline, the 1-year incidence of low back pain was 20 times higher than the incidence of neck and shoulder pain. This gives rise to the hypothesis that there are different health behaviors and norms for different musculoskeletal disorders.
Sick leave in a certain country depends not only on individual health behavior; it can also be affected by the approval of physicians and the insurance system. It seems that physicians in Iran easily agree to approve low back pain on the basis of patient reports alone, as compared with neck and shoulder pain, where different tests are recommended and requested before a final decision is made.
The participation rate in the baseline study was high (79.8%) but the difference in incidence between participants and nonparticipants in the follow-up study is considerable (0.8% compared with 4.2%). Reports from the human resource department revealed no obvious differences in demographic or workplace factors between participants and nonparticipants. A severe bias can be introduced in studies with a low response rate. At least in this study, healthy workers were more likely to participate.
neck and shoulder pain and disorders are more prevalent among women compared with men. Cassou et al showed that prevalence and incidence of neck and shoulder pain were twice as high in women as in men. In our study, women reported neck and shoulder pain 2 times more than men in the baseline survey, but only 4 sick-listed cases were detected in the follow-up study. At IKCo, women work as office workers and technicians, and as a whole there are low sick leave rates in these jobs.
Pain in the neck or shoulder in the baseline study was a significant factor for being on sick leave because of neck/shoulder pain. This is more significant for having disabling pain compared with nondisabling pain. Although the number of cases is small (i.e., there is a wide confidence interval), this significance is rather interesting.
With regard to the questions we asked in the baseline study about pain in different regions of extremities, our analysis (not included in this paper) shows that having pain in these regions of upper limbs, including the elbow and wrist, does not constitute a risk factor for neck and shoulder pain sick leave.
As far as low back pain is concerned, studies show that workers with low back pain and concurrent musculoskeletal complaints from another anatomic region (including spinal comorbidity) are more likely to remain sick-listed than subjects with solely low back pain. On the other hand, Ijzelenberg et al did not find that concurrent low back pain and neck and shoulder pain increased the risk of sickness absence.
In a study by Bergstrom et al, the most consistent risk factors for new episodes of sick leave because of neck or back pain found during 2 periods of follow-up (18 months and 3 years) were blue-collar work and several earlier episodes of neck or back pain assessed at baseline. In this study we did not find any significant relation between previous back pain and the risk of future sick leave because of neck and shoulder pain.
The results of our study on comorbidity in sick leave cases show that comorbidity is more prevalent in sick leave cases because of neck and shoulder pain (e.g., high rate of depression, previous sickness absence and spine pain, demands for changing jobs) than in other employees, although further studies are required to improve this hypothesis.
During the 4-year follow-up, 2200 employees left the company. The main reason for this in more than 80% of the cases was retirement. In Iran, all employees who have 30 years of work experience or are above the age of 60, can retire. Among industrial workers, this duration was 25 years at the start of the study period. In accordance with new rules that were approved by the government during our study period, all employees with more than 20 years of hard physical work experience (based on a national expert committee’s definitions) could also retire. For this reason, a large number of workers retired during the 4 years. A small number of employees left the company and transferred to other plants outside IKCo. It is logical to assume that those who left the company, taken as a whole, were older than other participants, and this may affect the incidence of sick leave.
In the baseline study, age and work experience were risk factors for self-reported neck and shoulder pain but there was no significant relation with sick leave; with considering the total number of employees and the number of retired employees it cannot describe the reason or at least the main reason for the low incidence.
In the baseline study, several physical and psychosocial risk factors at work for neck and shoulder pain were found. In this study of sick leave, repetitive work, sitting position at work, and unattractive work were the only factors that influenced the outcome and remained as risk factors.
Different studies have shown relations between physical and psychosocial factors at work, and both incidence and prevalence of neck and shoulder pain. In 1 review, the risk factors for sick leave because of neck and shoulder pain were shown to be poor social support and low decision latitude over work content and organizational factors. Former studies have also shown that there is a difference between these factors in self-reported pain and sickness absence because of pain. Our study is also in line with these reports.
In this study we only measured risk factors at the beginning of the project in 2003. IKCo is a large company with its special characteristics. Compared with other companies in Iran, it is more stable and prestigious; nevertheless, like most companies IKCo undergoes different changes such as reorganization, downsizing and outsourcing programs that affect physical and psychosocial work factors. The exposures for the specific individuals may have changed and may thereby bias the results. Repeated measurement of exposures is one possible way of helping to identify this dynamic pattern and its influence on the outcome.
IKCo is a company with various jobs, including specialists, technicians, office workers, and unskilled workers, but there is no guarantee that it is representative of other industries and populations of Iranian workers.
