Estimating intervention effects in a complex multi-level smoking prevention study.

This paper illustrates how to estimate cumulative and non-cumulative treatment effects in a complex school-based smoking intervention study. The Instrumental Variable method is used to tackle non-compliance and measurement error for a range of treatment exposure measures (binary, ordinal and continuous) in the presence of clustering and dropout. The results are compared to more routine analyses. The empirical findings from this study provide little encouragement for believing that poorly resourced school-based interventions can bring about substantial long-lasting reductions in smoking behaviour but that novel components such as a computer game might have some short-term effect.

Predicting the onset of knee pain: results from a 2-year prospective study of new workers.

OBJECTIVE: To determine the relative contribution of work-related mechanical (injury) factors and psychosocial factors to the onset of a new episode of knee pain, in a cohort of newly employed workers. METHODS: A prospective cohort study of newly employed workers from 12 diverse occupational settings in England (The New Workers Study). 859 newly employed workers, free of knee pain, were identified. Information about occupational mechanical factors (manual handling and postural activities), the occupational physical environment, and psychological and psychosocial factors was collected by self-completion questionnaires. Participants were followed up after 12 and 24 months to identify cases of knee pain onset. Generalised estimating equations were used to estimate the risk of new-onset knee pain, with respect to the exposures previously measured. RESULTS: In total, over the 2-year follow-up period, 108 cases of new-onset knee pain were observed. Mechanical load, postural factors, psychological distress and work-place psychosocial factors all influenced the risk of new-onset knee pain over the 2-year follow-up period. On multivariate analysis, two factors remained independently predictive of knee pain onset: lifting or carrying heavy weights in one hand, and the level of general psychological distress. CONCLUSION: In addition to mechanical (injury) factors, psychological factors are important risk factors for knee pain onset as shown in a population of young newly employed workers.

Mechanical injury and psychosocial factors in the work place predict the onset of widespread body pain: a two-year prospective study among cohorts of newly employed workers.

OBJECTIVE: Mechanical injury has been postulated as a risk factor for widespread pain, although to date, the evidence is weak. The aim of this study was to determine whether repeated exposure to mechanical trauma in the work place predicts the onset of widespread pain and to determine the relative contribution of mechanical trauma compared with psychosocial factors. METHODS: In this prospective cohort study of 1,081 newly employed subjects in 12 diverse occupational settings, we collected detailed information on mechanical exposure, posture, physical environment, and psychosocial risk factors in the work place. Study questionnaires were completed at baseline and at 12 and 24 months. Individuals free of widespread pain at baseline and 12 months were eligible for followup. Generalized estimating equations were used to determine which factors predicted the new onset of widespread pain. RESULTS: Of the 1,081 baseline respondents, 896 were free of widespread pain and were eligible for further study. Of these 896 subjects, 708 and 520 responded at 12 months and 24 months, respectively. The rates of new-onset widespread pain were 15% at 12 months and 12% at 24 months. Several work place mechanical and posture exposures predicted the new onset of widespread pain: lifting >15 lbs with 1 hand, lifting >24 lbs with 2 hands, pulling >56 lbs, prolonged squatting, and prolonged working with hands at or above shoulder level. Of the psychosocial exposures, those who reported low job satisfaction, low social support, and monotonous work had an increased risk of new-onset widespread pain. In multivariate analysis, monotonous work and low social support were found to be the strongest independent predictors of symptom onset. CONCLUSION: Our findings demonstrate that the prevalence of new-onset widespread pain was high, but among this young, newly employed work force, both physical and psychosocial factors played an important role.

Predicting the onset of forearm pain: a prospective study across 12 occupational groups.

OBJECTIVE: To determine, among workers free of forearm pain, the role of mechanical and psychosocial factors in predicting future onset. METHODS: A prospective cohort study was conducted among 782 newly employed workers from 12 occupational groups. At baseline, a cohort of 782 workers free of forearm pain was identified and measurement was made about physical and psychosocial aspects of their job and working environment. Subjects were recontacted after 1 year to determine new onsets of forearm pain. A sample of those reporting new onset forearm pain underwent a structured examination of the upper limb. RESULTS: One year after baseline, 666 (85%) subjects were followed up. The overall prevalence of new onset forearm pain was 8.3% (n = 55). The strongest mechanical risk factor was frequent repetitive movements of the arm or wrist (odds ratio [OR] 2.9, 95% confidence interval [95% CI] 1.6-5.2). The strongest psychosocial risk factors were work considered monotonous at least half of the time (OR 3.0, 95% CI 1.6-5.7) or work with little autonomy (OR 2.6, 95% CI 1.1-6.1). Three specific independent risk factors (monotonous work, repetitive wrist movement, working with hands above shoulder level) could distinguish groups of subjects at substantially different risks of onset. CONCLUSIONS: Along with repetitive movements of the arms and wrists, mechanical postural factors and psychosocial factors also are important risk factors for onset of forearm pain. Our study emphasizes the multifactorial nature of risks for onset of forearm pain, and provides leads as to possible mechanisms for prevention.

Predictors of hip joint replacement in new attenders in primary care with hip pain.

BACKGROUND: Studies investigating the factors associated with need for total hip replacement should ideally be based on prospective investigation of new attenders in primary care. AIM: To determine the incidence of listing for total hip replacement, and its predictors, among attenders in primary care with a new episode of hip pain. DESIGN OF STUDY: Prospective multicentre cohort study. SETTING: One hundred and ninety-five patients (mean age = 63 years, 68% female) with new episode of hip pain, attending primary care between November 1994 and October 1997. At the first visit, patients were evaluated for indices of pain and disability, range of hip movement, and radiographic changes of osteoarthritis. METHOD: General practitioner participants were recruited from the membership of the Primary Care Rheumatology Society to recruit all consecutive attenders with a new episode of hip pain. Annual follow-up was carried out to determine which patients were being 'put on a waiting list' for total hip replacement. RESULTS: Seven per cent of patients were put on a waiting list for total hip replacement within 12 months and 23% of patients within four years. At presentation, pain duration, pain severity, (including the need to use a stick) and restriction of internal rotation were the major clinical predictors of being put on a waiting list. Radiographic predictors of osteoarthritis performed similarly to the clinical measures. A simple scoring system based on both radiographic severity and two of the clinical measures was derived that identified groups at high likelihood of being put on a waiting list (sensitivity = 76%) with a low false-positive rate (specificity = 95%). CONCLUSION: New primary care attenders with pain are frequently accepted for total hip replacement soon after their first attendance--a decision that can be predicted by simple clinical measures.