Time-trend of sleep disorder in relation to night work: a study of sequential 1-year prevalences within the GAZEL cohort.

We examined two longitudinal hypotheses: the 1-year prevalence for night workers is consistently higher than for others; the time trend is steeper for night workers than for others. Subjects were 12,779 men (age 40-50) working at Electricité de France-Gaz de France, and recruited in the GAZEL cohort. Five questionnaires were sent to all subjects on 1989 through 1993. Self-reported occurrence of sleep disorder in the previous year was regressed on night work status in 1989 and covariates to estimate prevalence rate differences (PRDs). The estimated PRD for regular night workers versus others was 6.1% (95% CI, 1.1-11.1%). There was a common time trend of 1.4% per year (1.0-1.9%), and evidence of excess trend for regular night workers: 1.1% (-0.7-2.9%). Findings indicate that the effect of night work on sleep complaints manifests itself during the first year of night work and is permanent.

The effect of perceived challenges and skills on the quality of subjective experience.

This article investigates the effects that perceived challenges and skills in activities have on the quality of everyday life experience. Based on flow theory it was predicted that quality of daily experience would depend on the challenge experienced and skill required in specific situations, as well as on the balance between challenge and skill. The Experience Sampling Method (ESM) was used on a sample of 208 talented adolescents to measure daily variations in four dimensions of experience (concentration, wish to do the activity, involvement, and happiness) in four contexts (in school, with relatives, with friends, and in solitude). The four dimensions of experience were regressed on the predictors challenges, skills, and their absolute difference expressing the balance/imbalance of challenges and skills. Hierarchical linear modeling, explained in detail herein, was conducted on a 1-week sample of experiences. Findings confirm the prediction of flow theory that the balance of challenges and skills has a positive and independent effect on the quality of experience. Yet some differences of parameter estimates were found between dimensions of experience and between social contexts. These heterogeneities call for a further improvement of the flow model.

The role of psychological distress and personality in the incidence of sciatic pain among working men.

OBJECTIVES: The role of personality characteristics and psychological distress in the incidence of sciatic pain was investigated in a 3-year prospective study. METHODS: The study population consisted of 1149 Finnish men aged 25 through 49 years (387 machine operators, 336 carpenters, and 426 office workers) with no history of sciatic pain at the beginning of follow-up. The psychological distress and personality characteristics were assessed by the Middlesex Hospital Questionnaire and the Maudsley Personality Inventory. RESULTS: The 3-year cumulative incidence rate for sciatic pain was 22% among the machine operators, 24% among the carpenters, and 14% among the office workers. The multivariate analysis of psychological factors, taking into account individual and occupational factors, showed that only hysteria was significantly associated with the incidence of sciatic pain among the blue-collar workers. Among the white-collar workers, none of the psychological dimensions were associated with sciatic pain. CONCLUSIONS: These results are in accordance with previous relationships found between hysteria and low-back disorders. Further follow-up investigations are needed to elucidate the role of psychological factors in the occurrence of back problems.

Isokinetic performance in low back pain patients: The predictive power of the Self-Efficacy Scale.

The Self-Efficacy Scale (SES) has been found to predict isokinetic performance better than anthropometric variables. This study tests the predictive power of SES further against other measures of efficacy expectancies as well as measures of depression and perceived disability. A group of 105 chronic back pain patients was administered Beck's Depression Inventory (BDI), SES, the Pain Self-Efficacy Questionnaire (PSEQ), and the Oswestry low back pain disability questionnaire (OSWESTRY). Total isokinetic work done was measured at slow, medium and high speeds, for which multiple regression models were fitted controlling for sex, age, weight and height. The results confirmed SES to be the best overall predictor of isokinetic performance. BDI was not significant as a predictor of isokinetic performance. The models also revealed that SES predicts less well with increases in the test speed, particularly in extension. These results provide further evidence of the diagnostic value of SES relative to OSWESTRY and PSEQ.

Reported pain during lumbar discography as a function of anular ruptures and disc degeneration. A re-analysis of 833 discograms.

STUDY DESIGN: This re-analysis was based on 833 computed tomography/discograms collected from 306 candidates for back surgery. OBJECTIVES: The goal was to test the hypothesis that outer anular ruptures are the main determinant of the pain of discography. SUMMARY OF BACKGROUND DATA: Previous analyses indicated univariate associations of pain with disc degeneration and anular ruptures. METHODS: If present, pain was classified as "exact", "similar", or "dissimilar" reproduction of the previously experienced pain. For each disc, ruptures and degeneration were separately evaluated by a four-point scale. Multiple logistic regression with random effects was used in the analysis. RESULTS: Outer anular ruptures were the only predictor of the responses "similar" and "exact". General disc degeneration was the only predictor of the response "dissimilar". There was no effect modification due to gender, age, and spinal level. CONCLUSIONS: During discography, the outer anulus appears to be the origin of pain reproduction.

Anthropometric variables, self-efficacy beliefs, and pain and disability ratings on the isokinetic performance of low back pain patients.

OBJECTIVES: This study investigated how age, sex, height, body weight, self-efficacy beliefs, pain, and subjective disability predict the performance of low back pain patients on an isokinetic trunk muscle test. METHODS: One hundred and five patients participated in the study. Dependent variables were isokinetic flexion and extension strength measured as total work done at speeds 50, 100, and 150 degrees/second. RESULTS: The anthropometric measures were poor predictors, height being the only significant one. Body weight and age were of no relevance for the performance. Subjective pain and disability had negative effects on the performance of men, but not of women. Self-efficacy beliefs, i.e., the patient's belief in his or her capability to endure physical activities, was the most powerful predictor. CONCLUSION: For the purpose of validation, standardization, and interpretation of isokinetic performance in low back pain patients, these factors should be taken into account.

Seasonal variation in neck and shoulder symptoms.

The objective of the investigation was to study the course of neck and shoulder 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 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. Seasonal variation in symptoms should be considered when preventive programs against neck and shoulder disorders are planned and evaluated.

1991 Volvo Award in clinical sciences. Smoking and lumbar intervertebral disc degeneration: an MRI study of identical twins.

The primary objective of this study was to determine whether disc degeneration, as assessed through magnetic resonance imaging, is greater in smokers than in nonsmokers. To control for the maximum number of potentially confounding variables, pairs of identical twins highly discordant for cigarette smoking were selected as study subjects. Data analyses revealed 18% greater mean disc degeneration scores in the lumbar spines of smokers as compared with nonsmokers. The effect was present across the entire lumbar spine, implicating a mechanism acting systemically. This investigation demonstrates the efficiency of using carefully selected controls in studying conditions of multifactorial etiology, such as disc degeneration.