Linda Merlino

Cigarette smoking and the risk of rheumatoid arthritis among postmenopausal women: Results from the Iowa Women's Health Study

PURPOSE To determine whether cigarette smoking increases the risk of rheumatoid arthritis among postmenopausal women. SUBJECTS AND METHODS We followed a cohort of 31 336 women in Iowa who were aged 55 to 69 years in 1986 and who had no history of rheumatoid arthritis. Through 1997, 158 cases of rheumatoid arthritis were identified and validated based on review of medical records and supplementary information provided by physicians. Multivariable Cox proportional hazards regression was used to derive rate ratios (RRs) and 95% confidence intervals (CIs) for the association between cigarette smoking and rheumatoid arthritis. RESULTS Compared with women who had never smoked, women who were current smokers (RR = 2.0; 95% CI: 1.3 to 2.9) or who had quit 10 years or less before study baseline (RR = 1.8; 95% CI: 1.1 to 3.1) were at increased risk of rheumatoid arthritis, but women who had quit more than 10 years before baseline were not at increased risk (RR = 0.9; 95% CI: 0.5 to 2.6). Both the duration and intensity of smoking were associated with rheumatoid arthritis. Multivariable adjustments for age, marital status, occupation, body mass index, age at menopause, oral contraceptive use, hormone replacement therapy, alcohol use, and coffee consumption did not alter these results. CONCLUSION These results suggest that abstinence from smoking may reduce the risk of rheumatoid arthritis among postmenopausal women.

Coffee, tea, and caffeine consumption and risk of rheumatoid arthritis: Results from the Iowa Women's Health Study

OBJECTIVE To evaluate whether coffee, tea, and caffeine consumption are risk factors for rheumatoid arthritis (RA) onset among older women. METHODS These factors were evaluated in a prospective cohort study that was initiated in 1986 and that included 31,336 women ages 55-69 years without a history of RA. Risk factor data were self-reported using a mailed questionnaire. Through 1997, 158 cases of RA were identified and validated against medical records. The relative risk (RR) and 95% confidence interval (95% CI) were used as the measures of association and were adjusted for age, alcohol use, smoking history, age at menopause, marital status, and the use of hormone replacement therapy. RESULTS Compared with those reporting no use, subjects drinking > or =4 cups/day of decaffeinated coffee were at increased risk of RA (RR 2.58, 95% CI 1.63-4.06). In contrast, women consuming >3 cups/day of tea displayed a decreased risk of RA (RR 0.39, 95% CI 0.16-0.97) compared with women who never drank tea. Caffeinated coffee and daily caffeine intake were not associated with the development of RA. Multivariable adjustment for a number of potential confounders did not alter these results. The associations of RA onset with the highest categories of decaffeinated coffee consumption (RR 3.10, 95% CI 1.75-5.48) and tea consumption (RR 0.24, 95% CI 0.06-0.98) were stronger in women with seropositive disease compared with those with seronegative disease (RR 1.54, 95% CI 0.62-3.84 and RR 0.93, 95% CI 0.27-3.20, respectively). CONCLUSION Decaffeinated coffee intake is independently and positively associated with RA onset, while tea consumption shows an inverse association with disease onset. Further investigations of decaffeinated coffee and tea intake as arthritis risk factors are needed to verify these findings and explore their biologic basis.

Prevalence and incidence of carpal tunnel syndrome in US working populations: pooled analysis of six prospective studies

OBJECTIVES Most studies of carpal tunnel syndrome (CTS) incidence and prevalence among workers have been limited by small sample sizes or restricted to a small subset of jobs. We established a common CTS case definition and then pooled CTS prevalence and incidence data across six prospective studies of musculoskeletal outcomes to measure CTS frequency and allow better studies of etiology. METHODS Six research groups collected prospective data at > 50 workplaces including symptoms characteristic of CTS and electrodiagnostic studies (EDS) of the median and ulnar nerves across the dominant wrist. While study designs and the timing of data collection varied across groups, we were able to create a common CTS case definition incorporating both symptoms and EDS results from data that were collected in all studies. RESULTS At the time of enrollment, 7.8% of 4321 subjects met our case definition and were considered prevalent cases of CTS. During 8833 person-years of follow-up, an additional 204 subjects met the CTS case definition for an overall incidence rate of 2.3 CTS cases per 100 person-years. CONCLUSIONS Both prevalent and incident CTS were common in data pooled across multiple studies and sites. The large number of incident cases in this prospective study provides adequate power for future exposure-response analyses to identify work- and non-work-related risk factors for CTS. The prospective nature allows determination of the temporal relations necessary for causal inference.

Mortality risk associated with rheumatoid arthritis in a prospective cohort of older women: results from the Iowa Women’s Health Study

Objective: To determine whether rheumatoid arthritis (RA) is associated with excess mortality among older women. Methods: RA associated mortality was examined in a prospective cohort study that was started in 1986, and included 31 336 women aged 55–69 years without a history of RA at baseline. Up to 1997, 158 cases of RA were identified and validated against medical records. The relative risk (RR) and 95% confidence interval (CI) were calculated as measures of association between RA onset and subsequent mortality (overall and cause-specific) using Cox proportional hazards regression. Results: Compared with non-cases, women developing RA during follow up had a significantly increased mortality risk (RR=1.52; 95% CI 1.05 to 2.20). Mortality was higher among rheumatoid factor (RF) positive cases (RR=1.90; 95% CI 1.24 to 2.92) than among RF negative cases (RR=1.00; 95% CI 0.45 to 1.99). There were trends towards increased proportions of RA related deaths from infection (RR=3.61; 95% CI 0.89–14.69) and circulatory disease (RR=1.46; 95% CI 0.76 to 2.81) but not malignancy (RR=0.97; 95% CI 0.46 to 2.04). Conclusions: RA was associated with significantly increased mortality in a cohort of older women, and the association appeared to be restricted to those with RF positive disease.

Estrogen and other female reproductive risk factors are not strongly associated with the development of rheumatoid arthritis in elderly women

OBJECTIVE Endogenous and exogenous reproductive hormones have been associated with rheumatoid arthritis (RA) in women, but data are inconsistent and no studies have assessed RA risk factors exclusively in elderly women. METHODS The authors examined the association between reproductive factors, exogenous hormone exposure, and RA in a prospective cohort study of 31,336 Iowa women who were aged 55 to 69 years at cohort baseline in 1986. RESULTS During 11 years of follow-up, 158 incident cases of RA were identified and validated. Age at last pregnancy (P trend =.01) and age at menopause (P trend =.03) were inversely associated with RA, whereas a history of polycystic ovary syndrome (relative risk [RR], 2.58; 95% confidence interval [CI], 1.06 to 6.30), endometriosis (RR, 1.72; 95% CI, 0.93 to 3.18), and former use of hormone replacement therapy (RR, 1.47; 95% CI, 1.04 to 2.06) were positively associated with RA. In multivariate analysis models, a history of polycystic ovary syndrome remained the most consistent predictor of RA, whereas the RRs for other factors attenuated. CONCLUSION Few reproductive factors showed a strong or statistically significant association with RA in elderly women. The association of polycystic ovary syndrome may be indicative of perturbations of endocrine-immune activity that may influence the development of RA. This prospective cohort study adds to the understanding of the potential contribution of hormonal factors to the cause of RA in older women.

Biomechanical risk factors for carpal tunnel syndrome: a pooled study of 2474 workers.

Background Between 2001 and 2010, five research groups conducted coordinated prospective studies of carpal tunnel syndrome (CTS) incidence among US workers from various industries and collected detailed subject-level exposure information with follow-up of symptoms, electrophysiological measures and job changes. Objective This analysis examined the associations between workplace biomechanical factors and incidence of dominant-hand CTS, adjusting for personal risk factors. Methods 2474 participants, without CTS or possible polyneuropathy at enrolment, were followed up to 6.5 years (5102 person-years). Individual workplace exposure measures of the dominant hand were collected for each task and included force, repetition, duty cycle and posture. Task exposures were combined across the workweek using time-weighted averaging to estimate job-level exposures. CTS case-criteria were based on symptoms and results of electrophysiological testing. HRs were estimated using Cox proportional hazard models. Results After adjustment for covariates, analyst (HR=2.17; 95% CI 1.38 to 3.43) and worker (HR=2.08; 95% CI 1.31 to 3.39) estimated peak hand force, forceful repetition rate (HR=1.84; 95% CI 1.19 to 2.86) and per cent time spent (eg, duty cycle) in forceful hand exertions (HR=2.05; 95% CI 1.34 to 3.15) were associated with increased risk of incident CTS. Associations were not observed between total hand repetition rate, per cent duration of all hand exertions, or wrist posture and incident CTS. Conclusions In this prospective multicentre study of production and service workers, measures of exposure to forceful hand exertion were associated with incident CTS after controlling for important covariates. These findings may influence the design of workplace safety programmes for preventing work-related CTS.

Personal and workplace psychosocial risk factors for carpal tunnel syndrome: a pooled study cohort.

Background Between 2001 and 2010, six research groups conducted coordinated multiyear, prospective studies of carpal tunnel syndrome (CTS) incidence in US workers from various industries and collected detailed subject-level exposure information with follow-up symptom, physical examination, electrophysiological measures and job changes. Objective This analysis of the pooled cohort examined the incidence of dominant-hand CTS in relation to demographic characteristics and estimated associations with occupational psychosocial factors and years worked, adjusting for confounding by personal risk factors. Methods 3515 participants, without baseline CTS, were followed-up to 7 years. Case criteria included symptoms and an electrodiagnostic study consistent with CTS. Adjusted HRs were estimated in Cox proportional hazard models. Workplace biomechanical factors were collected but not evaluated in this analysis. Results Women were at elevated risk for CTS (HR=1.30; 95% CI 0.98 to 1.72), and the incidence of CTS increased linearly with both age and body mass index (BMI) over most of the observed range. High job strain increased risk (HR=1.86; 95% CI 1.11 to 3.14), and social support was protective (HR=0.54; 95% CI 0.31 to 0.95). There was an inverse relationship with years worked among recent hires with the highest incidence in the first 3.5 years of work (HR=3.08; 95% CI 1.55 to 6.12). Conclusions Personal factors associated with an increased risk of developing CTS were BMI, age and being a woman. Workplace risk factors were high job strain, while social support was protective. The inverse relationship between CTS incidence and years worked among recent hires suggests the presence of a healthy worker survivor effect in the cohort.

Musculoskeletal symptoms of the neck and upper extremities among Iowa dairy farmers

BACKGROUND The prevalence of musculoskeletal symptoms (MSS) among U.S. dairy farmers is relatively unknown. The purpose of this study was to assess the prevalence of neck and upper extremity MSS, and to examine associations between symptoms and dairy operation activities among dairy farmers. METHODS Questionnaires were mailed to randomly selected dairy farmers in the State of Iowa, USA. Demographic, site specific MSS, and dairy operation activity information was obtained. Odds ratios and 95% confidence intervals were estimated with logistic regression adjusting for potential confounders. RESULTS Among the participants (N = 341), shoulder MSS were reported most frequently (54%). Neck MSS were significantly associated with manually feeding (OR(adj) = 2.29; 95% CI = 1.09-4.80) and tractors use (OR(adj) = 2.17; 95% CI = 1.05-4.50). Also, wrist/hand MSS were associated with manually cleaning animal stalls (OR(adj) = 1.96; 95% CI = 1.06-3.63). CONCLUSIONS Neck and upper extremity MSS were common and associated with common dairy farming practices. Future studies need to more accurately assess exposures to physical risk factors for MSS so ergonomic interventions can be developed.

A Prospective Study of Musculoskeletal Outcomes Among Manufacturing Workers II. Effects of Psychosocial Stress and Work Organization Factors

Objective: The aim of this study was to characterize associations between psychosocial and work organizational risk factors and upper-extremity musculoskeletal symptoms and disorders. Background: Methodological limitations of previous studies of psychosocial and work organizational risk factors and musculoskeletal outcomes have produced inconsistent associations. Method: In this prospective epidemiologic study of 386 workers, questionnaires to assess decision latitude (“control”) and psychological job demands (“demand”) were administered to study participants and were used to classify them into job strain “quadrants.” Measures of job stress and job change were collected during each week of follow-up. Incident hand/arm and neck/shoulder symptoms and disorders were ascertained weekly. Associations between exposure measures and musculoskeletal outcomes were estimated with proportional hazard methods. Results: When compared to the low-demand/high-control job strain referent category, large increases in risk of hand/arm disorders were observed for both high-demand/high- control (hazard ratio [HR] = 4.49, 95% confidence interval [CI] = [1.23, 16.4]) and high-demand/low-control job strain categories (HR = 5.18, 95% CI = [1.39, 19.4]). Similar associations were observed for hand/arm symptoms. A strong association was also observed between the low-demand/low-control job strain category and neck/shoulder disorders (HR = 6.46, 95% CI = [1.46, 28.6]). Statistically significant associations were also observed between weekly stress level and weekly job change and several musculoskeletal outcomes. Conclusion: Associations between psychosocial risk factors and work organizational factors and musculoskeletal outcomes were large and in the hypothesized direction. Application: Prevention of occupational musculoskeletal disorders may require attention to psychosocial and work organizational factors in addition to physical factors. Methods to control adverse effects of psychosocial and work organizational risk factors should be explored.

Test-Retest Reliability of a Self-Administered Musculoskeletal Symptoms and Job Factors Questionnaire Used in Ergonomics Research

The purpose of this study was to investigate the test-retest reliability of questionnaire items related to musculoskeletal symptoms and the reliability of specific job factors. The type of questionnaire items described in the present study have been used by several investigators to assess symptoms of musculoskeletal disorders and problematic job factors among workers from a variety of occupations. Employees at a plastics molding facility were asked to complete an initial symptom and jobs factors questionnaire and then complete an identical questionnaire either two or four weeks later. Of the 216 employees participating in the initial round, 99 (45.8%) agreed to participate in the retest portion of the study. The kappa coefficient was used to determine repeatability for categorical outcomes. The majority of the kappa coefficients for the 58 questionnaire items were above 0.50 but ranged between 0.13 and 1.00. The section of the questionnaire having the highest kappa coefficients was the section related to hand symptoms. Interval lengths of two and four weeks between the initial test and retest were found to be equally sufficient in terms of reliability. The results indicated that the symptom and job factors questionnaire is reliable for use in epidemiologic studies. Like all measurement instruments, the reliability of musculoskeletal questionnaires must be established before drawing conclusions from studies that employ the instrument.