From: J Epidemiol Community Health. 2005 Sep;59(9):721-8

Work related musculoskeletal disorders and complaints constitute an important health problem in many industrialised countries, as they account for a large number of working days lost and considerable workers compensation and disability payments. For a long time, low back pain has been the dominant problem. However, pain from the shoulder and neck region now seems to occur more frequently. The prevalence of shoulder and neck symptoms is highest in the 45–65 year age bracket, as well as among women, manual workers, and certain ethnic groups.

However, its aetiology is still incompletely understood. Mechanical exposure at work and psychosocial conditions within and without the workplace, in addition to lifestyle and individual variables (age, previous symptoms, etc) are frequently discussed as causal factors in the literature.

Shoulder and neck symptoms have been linked to jobs with highly repetitive work, static work, and work above shoulder level. However, mechanical exposure explains only part of these complaints. The role of psychosocial factors in the workplace has therefore received increasing attention. On the job pressure, monotonous work, and a high perceived workload have also been associated with musculoskeletal symptoms just as much as working situations characterised by high psychological demands, low decision latitude, and low social support.

Hence, an aetiological model explaining shoulder and neck symptoms could be based on the assumption of an interaction between mechanical and psychosocial factors at work. There is, however, a need to clarify the interplay between these risk factors.

A number of shortcomings in previous research into the causes of back and neck pain have been recognised. Firstly, few studies have separated low back and neck pain, which would seem to be an important distinction because of potentially different epidemiological patterns and assumedly different risk factors. Secondly, studies regarding the role of psychosocial risk factors in these outcomes seldom have adequately controlled their risk estimates with respect to potential confounding from mechanical exposure.

Moreover, few studies have been performed on populations having a sufficient variety of both mechanical and psychosocial exposures. The presumed high correlation between the two risk factors cited can only be weighed adequately in a large study sample in which diverse job tasks are represented.

Finally, few attempts have been made to quantify the multidimensionality of mechanical exposure. Nor have such measures been used in relation to psychosocial ones—particularly not in a prospective study design.

This study has attempted to address all the mentioned issues. Based on a large general population cohort, its intentions are to analyse the importance of both mechanical and psychosocial exposures in the workplace on the incidence of shoulder and neck complaints, and evaluate the possible effect modification between these two exposures.

We found that mechanical exposure (for men) and job strain (for women)—in other words, the combination of high job demands and low job decision latitude—were the factors most strongly associated with a higher risk for developing shoulder and neck pain during the one year follow up period.

We also found evidence for a synergistic effect of these two factors in heightening the risk of developing shoulder and neck pain among women, but not among men.

Our results may have been biased by selection, misclassification, and confounding. It is probable that the most vulnerable people had left their jobs and thus were excluded from the cohort in this study—either because they were no longer pursuing a physically demanding vocation, or because they were already ill at the time of the baseline assessment. This would bias the risk estimates towards the null.

Furthermore, it is known that people who are ill have less of a tendency to participate in studies. A higher non-participation rate among people complaining of shoulder and neck pain during the follow up study could also lead to an underestimation of the true association between mechanical and psychosocial exposures and the incidence of shoulder and neck pain. In actuality, the high participation rate in our follow up study (86.6%) would render this possibility a negligible consideration.

Bias attributable to dependent misclassification should not influence the results of this prospective study, as the exposures were determined at baseline, and case status at follow up. However, another possibility of misclassification could be present, namely, between mechanical and psychosocial exposures. It is possible that exposure to one of these factors might affect the person’s assessment of the other. However, the correlation coefficient between these two exposures were rather moderate, which ought to exclude the possibility that the results were very much influenced by this type of bias.

Another bias of importance could be confounding. One potential confounder could be age, but adjustment for this factor in the multivariate analysis only resulted in a very marginal change in the ORs.

The most important confounder to account for was job strain regarding the estimated impact of mechanical exposure, and mechanical exposure regarding the impact of job strain. However, including these variables in the model only decreased the age adjusted ORs slightly, without changing their statistical significance. It can, thus, be concluded that the impact of mechanical exposure and job strain on shoulder and neck pain exhibits little or no confounding by each others’ effect.

Further potential confounding factors were marital status and country of origin. Once again, inclusion of these variables in the multivariate models hardly changed the ORs. Occupational status was not included in the multivariate analysis because of its close association with both mechanical and the psychosocial exposures. For this reason, the inclusion of occupational status in the multivariate model would most probably result in an over-adjusted model, or problems of multicolinearity. Educational level was therefore chosen as the variable denoting socioeconomic status in the confounding analysis. But even when this variable was added to the multivariate model, its effect on the risk estimate was moderate.

A number of previously published studies concerning shoulder and neck pain have included both mechanical and psychosocial exposures. Most of these have been performed within occupationally homogenous groups, such as newspaper workers, transit operators, forestry workers, carpenters, car workers, homecare workers, aluminium smelters, students, medical secretaries, and female nursing staff. However, there are a few studies that have used groups drawn from the general population.

Most of the aforementioned studies were cross sectional, and one was a case-referent study. In these investigations, the effect of mechanical exposure was controlled for psychosocial exposure, and vice versa. However, only two studies assessed possible effect modification between the two types of exposure. Both of these were cross sectional, and were based on occupationally homogenous samples (newspaper workers and female homecare workers).

Most of the studies mentioned used a kind of demand/control instrument to assess work related psychosocial exposure, while a great variety of measures were used for assessing mechanical workload. These ranged from time spent in a certain occupation to observational assessments of workload and postures. A wide array of instruments was also used in these studies to determine shoulder and neck pain. In some instances, a version of the standardised Nordic questionnaire was used.

In conclusion, there seems to be a lack of previous prospective studies that have been undertaken on large, general, population based samples (or at least samples representing a wide variety of occupations/work tasks), and that use well recognised instruments for assessing mechanical and psychosocial exposure. Such standards are required to optimally address the question of whether one or both of these exposures can be convincingly linked to shoulder and neck pain. The preceding caveat may especially hold true if the objective is a valid analysis of effect modification.

In a recently published review article concerning neck pain, in which 22 cross sectional, two prospective, and one case-referent study were evaluated, the authors concluded that awkward work postures could be linked to neck disorders with a reasonable degree of certainty. This coincides with our findings that mechanical exposure (as assessed by an index primarily based on awkward work postures) is associated with an increased risk of developing shoulder and neck pain during the follow up period, independent of psychosocial exposure.

In the case of women, we also found a statistically significant association between work related psychosocial factors such as job strain and the heightened risk of developing shoulder and neck pain during the follow up period, independent of mechanical exposure. Similarly, in some cross sectional studies, high psychosocial job demands were found to be associated with shoulder and neck pain, once again, independent of mechanical exposure. Several studies found low decision latitude associated with this outcome again, independent of mechanical exposure. Other studies, however, failed to find such an association. One prospective study, however, did find high decision latitude associated with an increased risk of shoulder and neck pain.

The most important finding in this study was that mechanical exposure has an impact on shoulder and neck pain in men and women, and so have work related psychosocial factors in women even when taking into account confounding for each others’ effect. Furthermore, evidence for the existence of a synergistic relation between these two types of exposures among women in a vocationally active, urban, middle aged, general population.

From: Ergonomics. 2008 May;51(5):637-48

The objective of this prospective cohort study was to evaluate if peak or cumulative musculoskeletal discomfort may predict future low back, neck or shoulder pain among symptom free workers. At baseline, discomfort per body region was rated on a 10 point scale six times during a working day. Questionnaires on pain were sent out three times during follow-up. Peak discomfort was defined as a discomfort level of 2 at least once during a day; cumulative discomfort was defined as the sum of discomfort during the day. Reference workers reported a rating of zero at each measurement.

Peak discomfort was a predictor of low back pain (relative risk (RR) 1.79), neck pain (RR 2.56), right or left shoulder pain (RR 1.91 and 1.90). Cumulative discomfort predicted neck pain (RR 2.35), right or left shoulder pain (RR 2.45 and 1.64). These results suggest that both peak and cumulative discomfort could predict future musculoskeletal pain.

From: Journal of Orthopedic Surgery. 2008 Jun 27;3(1):25 [Epub ahead of print]

Impingement syndrome and shoulder pain have been reported to occur in a proportion of patients following whiplash injuries to the neck. In this study they aim to examine these findings to establish the association between subacromial impingement and whiplash injuries to the cervical spine. They examined 220 patients who had presented to the senior author for a medico-legal report following a whiplash injury to the neck. All patients were assessed for clinical evidence of subacromial impingement. 56/220 patients (26%) had developed shoulder pain following the injury; of these, 11/220 (5%) had clinical evidence of impingement syndrome. Only 3/11 patients (27%) had the diagnosis made prior to evaluation for their medico-legal report. In the majority, other clinicians had overlooked the diagnosis. The seatbelt shoulder was involved in 83% of cases.

After a neck injury a significant proportion of patients present with shoulder pain, some of whom have treatable shoulder pathology such as impingement syndrome. The diagnosis is, however, frequently overlooked and shoulder pain is attributed to pain radiating from the neck resulting in long delays before treatment. It is important that this is appreciated and patients are specifically examined for signs of subacromial impingement after whiplash injuries to the neck. Direct seatbelt trauma to the shoulder is one possible explanation for its aetiology.

From: J Pediatr Orthop. 2008 July/August;28(5):512-517

Shoulder and back pain in school children is associated with wearing heavy backpacks. Such pain may be attributed to the magnitude of the backpack load and the manner by which children distribute the load over their shoulders and back. The purpose of this study is to quantify the pressures under backpack straps of children while they carried a typical range of loads during varying conditions.

Ten healthy children (aged, 12-14 years) wore a backpack loaded at 10%, 20%, and 30% body weight. Backpacks were carried under 2 conditions, low on back or high on back. Pressure sensors (0.1 mm thick) measured pressures beneath the shoulder straps.

When walking with the backpack straps over both shoulders, contact pressures were significantly greater in the low-back condition than in the high-back condition (P = 0.004). In addition, when children carried the backpack in the low-back condition, mean pressures (+/-SE) over the right shoulder were as follows: 98 +/- 31, 153 +/- 48, and 170 +/- 54 mm Hg at 10%, 20%, and 30% body weight, respectively, which were significantly higher than those over the left shoulder (46 +/- 14, 92 +/- 29, and 90 +/- 29 mm Hg, respectively). Perceived pain with the backpack over 1 shoulder was significantly greater than that for donning with both shoulders in the low back condition.

Pressures at 10%, 20%, and 30% body weight loads on the right or left shoulder, during low back or high back conditions, are higher than the pressure thresholds (approximately 30 mm Hg) to occlude skin blood flow. Furthermore, asymmetric and high pressures exerted for extended periods of time may help explain the shoulder and back pain attributed to backpacks. Ergonomic Backpacks are clinically proven to reduce backpack stress and are important for the prevention of back, neck and shoulder pain in children.

From: Clinical Journal of Pain. 2008 Mar-Apr;24(3):253-9.

To study the prevalence of upper extremity disorders and neck as a total and complaints of the arm, neck and/or shoulder not caused by acute trauma or any systemic disease as defined in the complaints of the arm, neck and/or shoulder model in the open population and to assess sociodemographic and health characteristics of chronic symptoms.

Data were obtained from the DMC3-study, a Dutch questionnaire survey on musculoskeletal conditions. Data on four anatomic sites were assessed: neck, shoulder, elbow, and wrist. Various health characteristics were measured including the Short Form-36. Rectangle diagrams were used to illustrate cooccurrence of pain in the four anatomic sites.

The 12-month prevalence of complaints of the arm, neck and/or shoulder was 36.8%, the point prevalence was 26.4%, and 19.0% patients reported chronic complaints of the arm, neck and/or shoulder. Women, aged 45 to 64 years, with the lowest education level and working were the most affected. Within those with upper extremity disorders, around 25% of cases were caused by an acute trauma or by some systemic disease. Of those with chronic complaints of the arm, neck and/or shoulder, 58% reported use of healthcare. Healthcare users scored worse on general health, limitations in daily living, pain, and sickness absence than nonhealthcare users; >43% reported symptoms in more than 1 anatomic site.

Upper extremity disorders and complaints of the arm, neck and/or shoulder frequently occur in the open population. Excluding acute traumas and systemic diseases reduced the prevalence of complaints of the arm, neck and/or shoulder and resulted in a relatively healthier population. A compound definition of complaints of the arm, neck and/or shoulder seems indicated because of the large overlap of affected anatomic sites.

From: Applied Ergonomics. 2002 Jan;33(1):75-84

Poor neck and shoulder postures have been suggested to be a cause of neck and shoulder pain in computer workers. The present study aimed to evaluate and compare the head, neck and shoulder postures of office workers with and without symptoms in these regions, in their actual work environments. The two all female subject groups reported significantly different discomfort scores across five trials repeated in a single working day. The results of repeated video capture and two-dimensional motion analysis showed that there were trends for increased head tilt and neck flexion postures in the symptomatic subjects (n = 8), compared to the asymptomatic subjects (n = 8). Symptomatic subjects also tended to have more protracted acromions compared with asymptomatic subjects and showed greater movement excursions in the head segment and the acromion. All subjects demonstrated an approximately 10% increase in forward head posture from their relaxed sitting postures when working with the computer display, but there were no significant changes in posture as a result of time-at-work.

From: BMC Musculoskelet Disord. 2008 Mar 17;9:34

In epidemiological studies on neck and shoulder disorders, physical examination by health professionals, although more expensive, is usually considered a better method of data collection than self-administered questionnaires on symptoms. However, little is known on the comparison of these two methods of data collection. The agreement between self-administered questionnaires and the physical examination on the presence of neck and shoulder disorders was assessed in the present study.

These results suggest a fair to good agreement between the presence of musculoskeletal disorders ascertained by self-administered questionnaire and physical examination that may reflect differences in the constructs measured. Shorter time lags result in better agreement. Investigators should consider these results before choosing a method to measure the presence of musculoskeletal disorders in the neck and shoulder region.

In epidemiological studies, data on neck-shoulder disorders are often collected by physical examination, by questionnaire or with both instruments. Physical examination by health professionals is usually recognized as more objective than questionnaires. However, questionnaires permit data collection on many participants for a fraction of the cost and time of a physical examination. Few epidemiological studies on neck and upper extremity musculoskeletal disorders have systematically compared the findings of questionnaires with those obtained by physical examination. Only four studies published in English have reported the sensitivity and specificity of a questionnaire compared to clinical examination of the neck and shoulder region to identify individuals with neck and shoulder disorders.

In this study of VDU users, the agreement between a self-administered questionnaire on musculoskeletal disorders of the neck and shoulder region and a physical examination of the same region was examined in a sample of university clerical workers. Prevalence figures observed with questionnaire definitions were lower than those obtained from physical examination definitions. Results show an overall Kappa of 0.44 and a global agreement of 72% between the two instruments. The agreement was not substantially improved by the addition of questionnaire criteria related to functional limitations. The agreement diminished when the physical examination definition excluded the manifestation of pain. The percent agreement tended to be higher among cases than among non-cases. Higher agreement was observed with shorter time lapses between the administrations of the tests.

The questionnaire used here was adapted from questionnaires used in previous studies. Some items were taken from the Standardized Nordic Questionnaire, which showed an acceptable degree of reliability for the neck and shoulder region. Furthermore, previous studies suggested that questions related to the presence, duration and intensity of symptoms provide reliable information on musculoskeletal symptoms. Thus, it is reasonable to consider that the questionnaire used in the present study had an acceptable level of reliability.

Previous studies also provide evidence of construct validity of subjective symptoms reported in questionnaires. Also, VAS are considered among the best instruments to measure pain. To reduce the impact of potential error in recall in this study, only symptoms in the last seven days were considered. Furthermore, the fact that the questionnaire prevalence of musculoskeletal disorders in the neck and shoulder region was comparable (17%) to what was observed in previous studies on VDU workers provides further support for the validity of outcome measures obtained from the questionnaire.

The results of the current study suggest a fair to good agreement between the presence of neck and shoulder disorders ascertained by self-administered questionnaire and physical examination. This finding is in accordance with those obtained in previous studies comparing data from questionnaire with clinical examination to identify cases of neck and shoulder disorders. These earlier studies have concluded that self-reported neck and shoulder symptoms by questionnaire gave fairly good to good picture of the neck and shoulders disorders prevalence.

According to previous studies, tests used in physical examination, especially measurement of range of motion and manual muscle testing, have poor to good reliability. However, the use of a rigorous standardized protocol, pretested by the examiner at the beginning of the current study, and the fact that only one person examined all the workers favored reliability. In their literature review, Gajdosik and Bohannon (1987) concluded that there was acceptable content validity for the measurement of range of motion. Nevertheless, the comparisons in the present study might have been compromised at least in part by measurement error which could explain some lack of association with symptoms.

The different questionnaire definitions permitted the assessment of the influence of functional limitations on the agreement. The definition that included limitations in ADL gave similar agreement values when compared to the primary definition. On the other hand, definitions that included limitations in work, household and leisure activities resulted in poorer agreement. The lack of improvement in the agreement observed with the addition of functional limitations criterion may be explained by the fact that the questionnaire definition was already somewhat restrictive (pain reported in the neck and shoulder region for at least three days during the last seven days, with the worst pain intensity greater than 50 millimeters on the 100-millimeter VAS). Under these circumstances, the addition of the ADL limitations may not have contributed more information than the primary definition. Alternatively, the physical examination findings may not correspond closely enough to the domains that limit ADL. Furthermore, limitations measured in a dichotomous format (yes/no items) may not have been sufficiently sensitive in comparison to the more refined ADL limitations question.

According to our results, the measure of pain intensity provoked by specific maneuvers during the physical examination offered the best agreement when compared with the self-administered questionnaire. A low agreement was obtained with the physical examination definition based solely on decrease in range of motion or muscular strength. These results are consistent with the hypothesis that musculoskeletal disorders are progressive and that patients may have symptoms before objective physical findings appear. Also, cases defined by physical examination of range of motion and muscular strength may have been overlooked by the questionnaire; this would be consistent with previous studies that showed a low correlation between pain intensity and extent of tissue damaged.

The definition based on questionnaire may not measure the same concept than the physical examination. While the physical examination measures the integrity and the absolute performance of the structures and tissues, self-reported symptoms are based on actual performance and sensation, much affected by pain perception. This distinction is supported by the large impact that pain has on the agreement. The results of this study suggest that pain intensity is an important feature in the agreement between a questionnaire on musculoskeletal disorders and a physical examination and support the construct validity of a case definition based on symptoms.

The present study was part of a larger investigation on the prevalence of musculoskeletal disorders among video display unit (VDU) users. The main objective of the present study was to assess the agreement between a self-administered questionnaire and the physical examination made by a health professional on the presence of musculoskeletal disorders of the neck and shoulder region. Secondary objectives were to assess the effects on the agreement of different questionnaire and physical examination definitions and the importance of the time interval elapsed between the administrations of the tests.

Results of this study show that the agreement between a questionnaire on musculoskeletal disorders for the neck and shoulder region and a physical examination is fair to good. Inclusion of items related to functional limitations in questionnaires appears to be of limited value to improve the agreement. It is the physical examination definition that included pain manifestations that offered the best agreement with the questionnaire. A shorter time interval between the administrations of the two tests also yields a better agreement. Investigators should consider these results before choosing a method to measure the presence of musculoskeletal disorders of the neck and shoulder region.

From: Hiroshima J Med Sci. 2006 Dec;55(4):101-7.

It is well known that psychological stress affects health status. Stiff neck and shoulder in a broad sense is one of the major somatic complaints among Japanese. The objective was to determine how much perceived stress and stiff neck and shoulder are associated with health-related quality of life (HRQoL) by gender. Participants (n = 512) completed the Japanese version of Perceived Stress Scale, the SF-8 Japanese version and original questions on perceived stiff neck and shoulder. Muscle hardness around the shoulder also was measured with the muscle tension meter. The multiple regression model of the men demonstrated that perceived stress was associated with not only the mental component summary (MCS) (beta: -0.494), but also the physical component summary (PCS) (beta = -0.319) of the SF-8. Although, in the model of the women, perceived stress was also associated with MCS (beta: -0.632) more than in that of the men, stiff neck and shoulder and age group (beta: -0.231; -0.268, respectively), but not stress, were related to PCS. The subjective neck and shoulder stiffness was hardly correlated with the objective shoulder muscle hardness. This study revealed the associations between perceived stress, stiff neck and shoulder and HRQoL, and their difference by gender. The hypothesis of gender differences was discussed with a focus on kind of stressors, perception of stress, admission of negative symptoms and cause of stiff neck and shoulder.

From: Scandanavian Journal of Work, Environ and Health. 1992 Aug;18(4):257-61

The objective of the investigation was to study the course of neck and shoulder pain symptoms and the predictors for these symptoms among women in light sedentary work. Postal surveys were conducted among 351 tellers (age 20-50 years) of a bank company in September, December, March, and May. The response rates were 74-90%. The outcome was the frequency of the symptoms during the previous three months. In the analysis, univariate explorations and random-effects logistic binomial regression for distinguishable responses were used. A change in the frequency of neck and shoulder pain symptoms was seen in 40.5% of the subjects during the follow-up period from autumn to spring. The frequency of the symptoms decreased from autumn and winter towards spring. The stability of the frequency of the symptoms was positively associated with age.

Chronic neck pain symptoms exhibit seasonal variation, worsening in the autumn and decreasing in the spring.

From: The Journal of Headache and Pain. 2008 Apr 14 [Epub ahead of print]

One common feature of chronic musculoskeletal pain and headaches are that they are both influenced by stress. Among these, tension headache, fibromyalgia and chronic neck and shoulder pain appear to have several similarities, both with regard to pathophysiology, clinical features and demographics. The main hypothesis of the present study was that patients with chronic pain (tension headache, fibromyalgia and shoulder neck pain) had stress-induced features distinguishing them from migraine patients and healthy controls. We measured pain, blood pressure, heart rate (HR) and skin blood flow (BF) during (1 h) and after (30 min) controlled low-grade cognitive stressor in 22 migraine patients, 18 tension headache patients, 23 fibromyalgia patients, 29 shoulder neck pain patients and 44 healthy controls. fibromyalgia patients had a lower early HR response to stress than migraine patients, but no differences were found among fibromyalgia, tension headaches, shoulder and neck pain patients. Finger skin BF decreased more in fibromyalgia patients compared to migraine patients, both during and after the test. When comparing chronic pain patients (chronic tension headaches, fibromyalgia and shoulder neck pain) with those with episodic pain (episodic tension headache and migraine patients) or little or no pain (healthy controls), different adaptation profiles were found during the test for systolic and diastolic blood pressure, HR and skin BF in the chronic group. In conclusion, these results suggest that tension headache, fibromyalgia and shoulder neck pain patients may share common pathophysiological mechanisms regarding the physiological responses to and recovery from low-grade cognitive stress, differentiating them from episodic pain conditions such as migraine.