neck and shoulder pain

98 Pages·2008·0.76 MB·English

From the Department of Clinical Neuroscience
Section of Personal Injury Prevention
Karolinska Institutet, Stockholm, Sweden
_______________________________________________________________________
NECK AND SHOULDER PAIN
Prevalence, incidence and risk factors
The IKCo cohort study

Akbar Alipour

Stockholm 2008
All previously published papers were reproduced with permission from the publisher.

Published by Karolinska Institutet. Printed by Universitetsservice US-AB
Nanna Svartz väg 4, SE-171 77 Stockholm, Sweden
Cover design by Ladan Alipour
© Akbar Alipour, 2008
ISBN 978-91-7409-126-7
ABSTRACT
This thesis presents the results of the prevalence and the incidence of neck/shoulder
pain (NSP) and its risk factors in an industrial population based cohort study. The
project was completed between 2003 and 2007 in Iran Khodro Car Manufacturing
Company (IKCo), the largest car company in Iran and the Middle East. At the
beginning of the study, the company employed more than 18,000 people.

The four papers are the results of a project that began with a baseline survey of self-
reported NSP prevalence and risk factors (Study I) and continued with a one-year and a
four-year follow up for sick leave cases due to NSP (Studies II and III). In addition, a
Persian-language version of a well-known questionnaire on musculoskeletal disorders
and risk factors (the MUSIC- Norrtälje questionnaire) was validated during the project
(Study IV).

Study I: The study population comprises all full-time employees of the company
(n=18,031). The measurement tool was the Nordic Questionnaire. A total of 14,384
(79.8%) of all employees completed the questionnaire. Depending on the questions
used to measure neck and shoulder symptoms, the results show that the prevalence
varied widely (from 20.5% to 3.9%). In the multiple logistic regression model, limited
to employees with at least one year of work experience, the indicators of risks that
remained for disabling pain of the neck/shoulder for males were: duration of
employment, high visual demands, repetitive work, sitting position at work, awkward
working position, no regular exercise, monotonous work, lack of an encouraging
organizational culture and anxiety concerning change. In females repetitive work,
sitting position at work and no support if there is trouble at work were the only factors
that remained. The results show similarities between prevalence and risk factors for
NSP between industries in middle-income countries and former studies, although a
young population of workers and job security can affect the results, especially for
disabling pain.

Studies II and III: The study population comprises all participants in Study I. One- year
incidence of sick leave due to NSP was extremely low (0.1%). This incidence occurred
only in unskilled and office workers. Results indicate that although the prevalence of
NSP and LBP was similar in the baseline study, a small number of NSP cases were
detected, compared to low back pain during the one-year follow-up. The study shows
that a simultaneous investigation of prevalence, incidence and recurrence could be a
good way to better understand the natural pattern of NSP.

In Study III, all the population was followed for four years. The four-year incidence
was also very low (0.8%), and only 98 cases of all employees (n=12,184) had one
episode of sick leave. Having the same prevalence for NSP in baseline compared to
other studies, but a low number of cases based on sick leave and low recurrence,
suggests the hypothesis that perhaps most workers continue to work regardless of pain,
although the population of young workers, insurance systems, health behaviour and job
insecurity are other factors that may affect the results. In the final regression model, the
remaining factors for potential physical risk were repetitive work and sitting positions
at work; in the case of psychosocial factors, unattractive work was the only significant
remaining factor. These results indicate that risk factors for sick leave were different
from risk factors for self-reported NSP prevalence in Study I.

Study IV: For a better understanding of NSP at work, repeated measurements with a
more elaborate questionnaire are needed. The MUSIC-Norrtälje Questionnaire was
chosen and tested for future studies. In the first step of the validity and reliability testing
of the questionnaire, two expert panel groups were established in Iran and Sweden. The
Focus Group Discussion (FGD) method was used to detect questionnaire face and
content validity. To detect questionnaire reliability, we used the test-retest method.
Except for two items, all other questions that respondents had problems with in the
focus group (20 of 297), had unclear translations; the ambiguity was related to the stem
of the questions and the predicted answers were clear for the participants. In the test-
retest study, the reliability coefficient was relatively high in most items (only 5 items
out of 297 had an ICC or kappa below 0.7). The final results of study indicate that the
Persian-language version of the MUSIC Questionnaire is a reliable and valid
instrument.

Most studies of NSP are cross-sectional and related to high-income and industrialized
countries. There is little information on NSP in low-/middle-income countries. The
results of this research into NSP from different aspects (self-reported prevalence of
NSP and risk factors, sick leave due to NSP and risk factors and comparison of NSP to
LBP) in the same population can help to increase our knowledge in relation to NSP.

Keywords: Neck/shoulder pain, self-reported, sickness absence, prevalence, incidence,
physical work factors, psychosocial factors, lifestyle, low-/middle-income countries,
occupational health, epidemiology.
LIST OF PUBLICATIONS
I. Alipour A, Ghaffari M, Shariati B, Jensen I, Vingard E. Occupational neck
and shoulder pain among automobile manufacturing workers in Iran. Am J Ind
Med, 2008. 51(5):372-9.

II. Ghaffari M, Alipour A, Farshad AA, Jensen I, Vingard E. Incidence and
recurrence of disabling low back pain and neck-shoulder pain. Spine, 2006.
31(21):2500-6.

III. Alipour A, Ghaffari M, Shariati B, Jensen I, Vingard E. Four-year incidence
of sick leave due to neck and shoulder pain and its association with work and
lifestyle. Submitted

IV. Alipour A, Ghaffari M, Jensen I, Shariati B, Vingard E. Reliability and
validity study of Persian modified version of MUSIC (musculoskeletal
intervention center) - Norrtalje questionnaire. BMC Musculoskelet Disord,
2007. 8:88.
CONTENTS

1 INTRODUCTION .................................................................. 3

2 BACKGROUND .................................................................. 7
2.1 The complexity of studying neck/ shoulder pain 7
2.2 Definition of Pain 7
2.3 Definition of neck/ shoulder pain 8
2.3.1 Anatomy of the neck/shoulder region 9
2.4 Health, illness, disease and sickness 10
2.4.1 Sick Leave 11
2.5 Prevalence 12
2.6 Incidence 13
2.7 Risk factors for neck/shoulder pain 15
2.7.1 General and demographic factors 15
2.7.2 Lifestyle factors 17
2.7.3 Individual physical and psychological factors 17
2.7.4 Physical work factors 17
2.7.5 Psychosocial factors at work 19
2.7.6 Theory behind the mechanism of risk factors 20
2.8 Questionnaires as a measurement tool 21
2.9 Musculoskeletal disorders and neck/shoulder 22
pain in middle-/low-income countries
2.10 General description of Iran - social security, 23
health care system and occupational health
2.11 The company studied 24

3 AIMS ................................................................................. 29
3.1 Overall aim 29
3.2 Specific aims 29

4 MATERIAL AND METHODS...................................................... 33
4.1 Study design 33
4.2 Study subjects 33
4.3 Data collection 34
4.3.1 Baseline survey for self-reported NSP prevalence and risk factors (Study I) 34
4.3.2 One-year and four-year follow-up studies for NSP incidence based 35
on sickness absence and its risk factors (Studies II and III)
4.3.3 Validity and reliability study of Persian modified version of MUSIC - Norrtälje 36
Questionnaire (Study IV)
4.4 Ethical approval 36
4.5 Statistical methods 36
5 RESULTS ............................................................................. 41
5.1 Study I 41
5.2 Studies II and III 47
5.3 Study IV 53

6 DISCUSSION......................................................................... 59
6.1 General consideration of results 59
6.1.1 Self-reported NSP prevalence 59
6.1.2 One-year and four-year follow-up of employees for sick leave due to 60
NSP (Incidence studies)
6.1.3 Risk factors 62
6.1.4 Validity and reliability study of Persian modified version of 63
MUSIC -Norrtälje Questionnaire
6.2 Methodological consideration 65
6.2.1 Study design 65
6.2.2 Study population 66
6.2.3 Non-participants 66
6.2.4 Measurement tools for risk factors 67
6.2.5 Generalizability of the study 67
6.3 Future plan 67

7 CONCLUSIONS................................................................... 71
7.1 General conclusion 71
7.2 Elephant in darkness 72

8 ACKNOWLEDGEMENTS....................................................... 75

9 REFERENCES .................................................................. 81
LIST OF ABBREVIATIONS
BMI Body Mass Index
CI Confidence Interval
HSE Health, Safety and Environment
ICC Interclass Correlation Coefficients
IEA International Ergonomics Association
IKCo Iran Khodro Car Manufacturing Company
LBP Low Back Pain
MSDs Musculoskeletal Disorders
MUSIC Musculoskeletal Intervention Center (research program)
NP Neck pain
NSP Neck/shoulder Pain
OR Odds Ratio
OWAS Ovako Working Posture Analyzing System
PEO Portable ergonomic observational method
SP Shoulder pain
WHO World Health Organization
___________________________________________________________INTRODUCTION
1.

INTRODUCTION
1
______________________________________________________________________

2