Design factors in epidemiologic cohort studies of work-related low back injury or pain

Lower back problems and work-related risks in a South African manganese factory

An analytical cross-sectional epidemiological study carried out among 109 manganese plant workers aimed to examine the prevalence and association between lower back problems (LBP) and occupational risk factors. Outcome was defined using a guided questionnaire and a functional rating index. Exposure to occupational risk factors was determined using self-reported questionnaires and workstation analyses. Multivariate logistic regression analyses indicated significant adjusted odds ratios (OR) for prolonged 90 degrees trunk flexion (OR 2.16; CI 1.15-4.05); manual handling (1.89; 1.17-3.08); load carriage (1.54; 1.08-2.19); and lifting (4.61; 1.37-15.47). The findings illustrate regional and occupational specifics of risk for LBP, and indicate that self-selection or adaptation to task-specific demands could possibly lead to observations of ergonomically relevant risk factors, which do not necessarily yield statistically significant associations with LBP. The findings further support multi-modal preventative approaches.

Risk factors for low back injury among farmers in Iowa: A case-control study nested in the agricultural health study

The aim of this study was to assess risk factors for low back injury requiring medical advice or treatment among Iowa farmers. Although farmers are at risk for low back injury, few studies have addressed risk factors for farm work-related low back injury. We screened 6999 participants in the Iowa portion of the Agricultural Health Study to identify 49 male farmers who reported farm work-related low back injury requiring medical advice or treatment in the previous year. We compared them with 465 uninjured male farmer controls. Multivariable modeling identified four risk factors significantly associated with low back injury: age less than 45 years (OR = 3.32; 95% CI 1.75-6.20), doctor-diagnosed asthma (OR = 4.26; 95% CI 1.49-12.10), education beyond high school (OR = 2.12; 95% CI 1.13-3.90), and difficulty hearing normal conversation (even with a hearing aid, in the case of those using one) (OR = 1.98; 95% CI 1.02-3.80). Although hearing difficulty may be a general risk factor for occupational injury, asthma may be a more specific risk factor for low back injury. Future research to assess the risk factors, asthma and difficulty hearing, may be particularly important, since farmers are at increased risk for hearing loss, and farmers come into contact with many inhaled agents that can cause asthma.

Systemic lupus erythematosus in a multiethnic U.S. cohort (LUMINA) XXXI: factors associated with patients being lost to follow-up

The objective of this study was to determine the frequency of loss to follow-up and the factors predictive of its occurrence in a systemic lupus erythematosus (SLE) multiethnic cohort. We studied SLE patients from the LUMINA cohort (Hispanics from Texas and from the Island of Puerto Rico, African-Americans and Caucasians). Loss to follow-up was defined as subjects who failed to attend two or more of the latest consecutive yearly study visits. The relationship between baseline features and loss to follow-up was examined by univariable and multivariable Cox regression analyses with loss to follow-up as the dependent variable. The retention rate in the cohort was estimated by the Kaplan-Meier method. Five-hundred and fifty-four patients with a mean (SD) follow-up of 3.4 (2.9) years were studied. One-hundred and fifty-eight (29%) met the definition of lost to follow-up. The cumulative loss to follow-up rate at five years was 36%. The cumulative loss to follow-up rate at five years was higher for the African-Americans. Patients lost to follow-up tended to be younger and more likely to have poor social support and higher levels of helplessness. They also tended to have more renal involvement and more active disease as per the Systemic Lupus Activity Measure-Revised. Disease activity (hazard ratio = 1.04, 95% confidence interval 1.01-1.07, P = 0.02) was the only variable independently contributing to loss to follow-up. Our data suggest that in longitudinal SLE studies, loss to follow-up does not occur at random and it differs between ethnic groups and is also particularly higher among patients with more active disease. Pro-active measures may need to be applied to decrease the probability of patients 'at risk' of becoming lost to follow-up and to preserve the integrity of the cohort.

Lower back problems and occupational risk factors in a South African steel industry

BACKGROUND

The etiology of work-related back disorders is often population specific. The objective of this study was to identify and establish the association of occupational risk factors with the prevalence of low back (LB) problems in a semi-automated South African Steel industry.

METHODS

The design entailed an analytical cross-sectional epidemiological study among a group of 366 steel plant workers. Outcome of LB problems was defined using a guided questionnaire and a functional rating index. Exposure to occupational risk factors was determined using self-reported questionnaires.

RESULTS

Multivariate logistic regression analyses indicated significant adjusted odds ratios (OR) for twisting and bending (OR 2.81; CI 1.02-7.73); bulky manual handling (5.58; 1.16-26.71); load carriage (7.20; 1.60-32.37); prolonged sitting (2.33; 1.01-5.37); kneeling and squatting (4.62; 1.28-16.60); and working on slippery and uneven surfaces (3.63; 1.20-10.90).

CONCLUSIONS

This study supports the current view of a multifactorial etiology in idiopathic LB problems, and emphasizes the importance of multiple intervention strategies in industrial settings.

Work factors as predictors of intense or disabling low back pain; a prospective study of nurses' aides

AIMS

To identify the work factors that predict intense low back pain (LBP) and LBP related sick leaves in nurses' aides.

METHODS

The sample comprised 4266 randomly selected Norwegian nurses' aides, not bothered or only a little bothered by LBP during the previous three months, and not on sick leave when completing a mailed questionnaire in 1999. Of these, 3808 (89.3%) completed a second questionnaire 3 months later and 3651 (85.6%) completed a third questionnaire 15 months later. Intensity of low back symptoms and certified sick leaves attributed to LBP during the observation period were assessed by self reports at the follow ups.

RESULTS

After adjustments for LBP during the three months prior to baseline, baseline health complaints, demographic and familial factors, and a series of physical, psychological, and social work factors, logistic regression analyses revealed the following associations: intense low back symptoms were predicted by frequent positioning of patients in bed, perceived lack of support from immediate superior, and perceived lack of pleasant and relaxing culture in the work unit. LBP related sick leaves were predicted by frequent handling of heavy objects, medium level of work demands, perceived lack of supportive and encouraging culture in the work unit, working night shifts, and working in a nursing home. Long term LBP related sick leaves were associated with changes of work or work tasks during the observation period that resulted in a perceived reduction of support and encouragement at work.

CONCLUSIONS

Not only frequent mechanical exposures, but also organisational, psychological, and social work factors, such as night shift work, perceived lack of support from superior, and perceived lack of a pleasant and relaxing or supporting and encouraging culture in the work unit, are associated with an increased risk of intense low back symptoms and LBP related sick leaves in nurses' aides.

Work factors as predictors of sickness absence: a three month prospective study of nurses' aides

AIMS

To identify the work factors that predict sickness absence in nurses' aides.

METHODS

The sample comprised 5563 Norwegian nurses' aides, not on leave because of illness or pregnancy when they completed a mailed questionnaire in 1999. Of these, 4931 (88.6%) completed a second questionnaire three months later. The outcome measure was the three month incidence proportion of certified sickness absence (>3 days), as assessed by self reports at follow up.

RESULTS

Perceived lack of encouraging and supportive culture in the work unit (odds ratio (OR) 1.73; 95% confidence interval (CI) 1.28 to 2.34), working in psychiatric and paediatric wards, having injured the neck in an accident, and health complaints were associated with higher risk of sickness absence, after adjustments for a series of physical, psychological, and organisational work factors, personal engagement in the work unit, demographic characteristics, and daily consumption of cigarettes. Having untraditional jobs (for nurses' aides) (OR 0.53; 95% CI 0.36 to 0.77), and engaging in aerobics or gym were associated with a lower risk of sickness absence.

CONCLUSIONS

The study suggests that the three month effects of work factors on rates of certified sickness absence are modest in nurses' aides. The most important work factor, in terms of predicting sickness absence, seems to be perceived lack of encouraging and supportive culture in the work unit.

The association between physical workload and low back pain clouded by the "healthy worker" effect: population-based cross-sectional and 5-year prospective questionnaire study

STUDY DESIGN

A population-based cross-sectional and 5-year prospective questionnaire study.

OBJECTIVE

To investigate self-reported physical workload as a risk factor for low back pain.

SUMMARY OF BACKGROUND DATA

Both physical and psychosocial workplace factors are considered risk factors for low back pain. However, today no consensus has been reached regarding the exact role of these factors in the genesis of low back pain.

METHODS

Questionnaire data were collected at baseline for 1397 (and after 5 years for 1163) men and women aged 31--50 years at baseline. Low back pain ("any low back pain within the past year," "low back pain < or = 30 days in total during the past year," "low back pain > 30 days in total during the past year") was analyzed in relation to physical workload (sedentary, light physical, and heavy physical work) using logistic regression and controlling for age, gender, and social group. The proportions of workers changing between the workload groups over the 5-year period were analyzed in relation to low back pain status.

RESULTS

At baseline no statistically significant differences in low back pain outcomes were found for workers exposed to sedentary, light physical, or heavy physical work. This was true for all age, gender, and social groups. At follow-up there was a statistically significant dose-response association between any low back pain and longstanding low back pain within the past year and increasing physical workload at baseline also after controlling for age, gender, and social group. Subjects with heavy physical workload at baseline changed statistically significantly more often to sedentary work if they experienced low back pain for more than 30 days out of the past year.

CONCLUSIONS

Having a sedentary job might have a protective or neutral effect in relation to low back pain, whereas having a heavy physical job constitutes a significant risk factor. Because of migration between exposure groups (the "healthy-worker" effect), longitudinal studies are necessary for investigating the associations between physical workload and low back pain.

Occupational disability related to back pain: application of a theoretical model of work disability using prospective cohorts of manual workers

BACKGROUND

A new model of work disability was developed based on the assumption that four different groups of workers are present at the beginning of a prospective epidemiologic study: one group of workers without back pain, and three groups of workers with back pain and a gradient of work disability. The goal of this research was to verify if these groups comprise workers at different levels of risk of occurrence of complete work disability related to back injury.

METHODS

Prospective cohorts of manual workers (n=578) were followed for 1 year to document the risk of occurrence of complete disability related to back injury.

RESULTS

The results showed that the workers who presented with back pain without work disability at the beginning of the study were at less risk compared to all the other workers in the cohort. Moreover, an effect modification was found between the workers who initially presented with back pain without work disability and a past history of compensation for back injury, adding credence to the non-similarity of these workers to the others.

CONCLUSIONS

Based on these results, further studies should focus on improving the knowledge of the characteristics of these workers leading to a better understanding of how to prevent occupational low-back pain.

The role of physical and psychological factors in occupational low back pain: a prospective cohort study

OBJECTIVE

To examine risk factors for onset of low back pain (LBP) in healthcare workers.

METHODS

Nursing students, during their 3 year training period, and 1 year after training were studied in a prospective cohort study, with repeated self reported measurements of determinants of LBP at 6 monthly intervals for 3 years during training, and after a 12 month interval there was an additional final follow up.

RESULTS

During training, increased risk of new episodes of LBP was associated with having had LBP at baseline, with part time work, and with a high score on the general health questionnaire (GHQ). A high GHQ score preceded the onset of LBP, in such a way that a high score at the immediately previous follow up increased risk of LBP at the next follow up. 12 Months after training, a history of recurring LBP during training increased the risk of a new episode as did having obtained work as a nurse. A high GHQ score at this follow up was also associated with a concurrently increased risk. Pre-existing GHQ score, either at the end of training or at baseline, had no effect on risk of LBP 12 months after training.

CONCLUSIONS

Other than a history of LBP, pre-existing psychological distress was the only factor found to have a pre-existing influence on new episodes of LBP. Increased levels of psychological distress (as measured by the GHQ) preceded the occurrence of new episodes of pain by only short intervening periods, implying a role for acute distress in the onset of the disorder. This finding suggests that management of the onset of occupational LBP may be improved by management of psychological distress.

Job characteristics as predictors of neck pain. A 4-year prospective study

Data from a community-based 4-year prospective study were used to investigate job characteristics as predictors of neck pain. Of 1791 working responders who completed a questionnaire in 1990, 1429 (79.8%) returned a second questionnaire 4 years later (1994). In responders without neck pain during the previous 12 months in 1990, the "little influence on own work situation" factor predicted neck pain during the previous 12 months (odds ratio = 2.21; 95% confidence interval, 1.18 to 4.14) and previous 7 days in 1994 (OR = 2.85; 95% confidence interval, 1.21 to 6.73) after adjustment for a series of potential confounders. In responders with neck pain in 1990, the little influence on own work situation factor was associated with persistent neck pain 4 years later. The study indicates that having little influence on one's own work situation is a predictor of neck pain.