Eric C. Sayre

Predictors of back pain in a general population cohort.

Study Design. The study used longitudinal data from the first and second cycles (1994–1995 and 1996–1997) of the Canadian National Population Health Survey. Objective. Our objective was to derive prediction models for back pain in the general male and female household populations. Summary of Background Data. Little is known about the predictors of back pain in the general population. Most previous studies focused on specific occupational groups and used a cross-sectional or case-control design. Methods. The study cohort consisted of all respondents aged 18+ years who reported no back problems in the 1994–1995 National Population Health Survey cycle (N = 11,063). Potential predictors of chronic back pain were classified into nine groups and entered into stepwise logistic regression models. Bootstrap methods were used to derive the final models and assess their predictive power. Results. The overall incidence of back pain was 44.7 per 1,000 person-years and was higher in women (47.0 per 1,000 person-years) compared with men (42.2 per 1,000 person-years). In men, significant predictors of back pain were age (peak effect in 45–64 years), height, self-rated health, usual pattern of activity (especially heavy work), yard work or gardening (negative association), and general chronic stress. In women, significant factors were self-reported restrictions in activity, being diagnosed with arthritis, personal stress, and history of psychological trauma in childhood or adolescence. Conclusions. Overall health and psychosocial factors are important predictors of back pain in both men and women. Other risk factors differ between the two sexes.

Immediate and past cumulative effects of oral glucocorticoids on the risk of acute myocardial infarction in rheumatoid arthritis: a population-based study

OBJECTIVES To determine the effect of glucocorticoids (GCs) on acute myocardial infarction (MI) risk in patients with RA. METHODS Using administrative health data, we conducted a population-based cohort study of 8384 incident RA cases (1997-2006). Primary exposure was incident GC use. MI events were ascertained using hospitalization and vital statistics data. We used Cox proportional-hazards models and modelled GC use as four alternative time-dependent variables (current use, current dose, cumulative dose and cumulative duration), adjusting for demographics, comorbidities, cardiovascular drug use, propensity score and RA characteristics. Sensitivity analyses explored potential effects of unmeasured confounding. RESULTS Within 50 238 person-years in 8384 RA cases, we identified 298 incident MI events. Multivariable models showed that current GC use was associated with 68% increased risk of MI [Hazard ratio (HR) = 1.68, 95% CI 1.14, 2.47]. Similarly, separate multivariable models showed that current daily dose (HR = 1.14, 95% CI 1.05, 1.24 per each 5 mg/day increase), cumulative duration of use (HR = 1.14, 95% CI 1.00, 1.29 per year of GC use) and total cumulative dose (HR = 1.06, 95% CI 1.02, 1.10 per gram accumulated in the past) were also associated with increased risk of MI. Furthermore, in the same multivariable model, current dose and cumulative use were independently associated with an increased risk of MI (10% per additional year on GCs and 13% per 5 mg/day increase). CONCLUSION GCs are associated with an increased risk of MI in RA. Our results suggest a dual effect of GCs on MI risk, an immediate effect mediated through current dosage and a long-term effect of cumulative exposure.

Validation of population-based disease simulation models: a review of concepts and methods

BackgroundComputer simulation models are used increasingly to support public health research and policy, but questions about their quality persist. The purpose of this article is to review the principles and methods for validation of population-based disease simulation models.MethodsWe developed a comprehensive framework for validating population-based chronic disease simulation models and used this framework in a review of published model validation guidelines. Based on the review, we formulated a set of recommendations for gathering evidence of model credibility.ResultsEvidence of model credibility derives from examining: 1) the process of model development, 2) the performance of a model, and 3) the quality of decisions based on the model. Many important issues in model validation are insufficiently addressed by current guidelines. These issues include a detailed evaluation of different data sources, graphical representation of models, computer programming, model calibration, between-model comparisons, sensitivity analysis, and predictive validity. The role of external data in model validation depends on the purpose of the model (e.g., decision analysis versus prediction). More research is needed on the methods of comparing the quality of decisions based on different models.ConclusionAs the role of simulation modeling in population health is increasing and models are becoming more complex, there is a need for further improvements in model validation methodology and common standards for evaluating model credibility.

Quality of Nonpharmacological Care in the Community for People with Knee and Hip Osteoarthritis

Objective. To assess the quality of nonpharmacological care received by people with knee and/or hip osteoarthritis (OA) in the community and to assess the associated factors. Methods. We conducted a postal survey to evaluate 4 OA quality-of-care indicators for knee/hip OA: (1) advice to exercise; (2) advice to lose weight; (3) assessment for ambulatory function; and (4) assessment for nonambulatory function, including dressing, grooming, and arising from a seated position. Eligible participants were identified from the administrative database of British Columbia between 1992 and 2006. Results. In total, 1349 participants reported knee and/or hip OA [knee only = 700 (51.9%); hip only = 261 (19.3%); knee and hip = 388 (28.8%)]. Their mean age was 67.1 years (SD 11.1); 816 (60.5%) were women, and 921 (68.3%) were diagnosed with OA for 6 years or longer. The overall pass rate of the 4 quality indicators was 22.4% (95% CI 20.5, 24.3). The pass rate for the individual quality indicator ranged from 6.9% for assessment of nonambulatory function to 29.2% for receiving assessment of ambulatory function. Receiving exercise advice was associated with having a university degree (vs high school diploma; OR 3.10, 95% CI 2.00, 4.80). Receiving weight-loss advice was associated with being female (OR 2.64, 95% CI 1.71, 4.08), being aged 55–64 years (compared to being aged 75 and over; OR 1.96, 95% CI 1.02, 3.76), and having higher Western Ontario and McMaster Universities Osteoarthritis Index scores (for every 10-point increment; OR 1.14, 95% CI 1.02, 1.26). On the other hand, having less than a high school education reduced the odds of weight-loss advice (OR 0.52, 95% CI 0.30, 0.88). Conclusion. The quality of nonpharmacological care for people with knee/hip OA in the community is suboptimal. Advice on exercise and weight management may not be provided equally across sex, age, disability, and formal education levels.

Assessment of health-related quality of life in arthritis: conceptualization and development of five item banks using item response theory

BackgroundModern psychometric methods based on item response theory (IRT) can be used to develop adaptive measures of health-related quality of life (HRQL). Adaptive assessment requires an item bank for each domain of HRQL. The purpose of this study was to develop item banks for five domains of HRQL relevant to arthritis.MethodsAbout 1,400 items were drawn from published questionnaires or developed from focus groups and individual interviews and classified into 19 domains of HRQL. We selected the following 5 domains relevant to arthritis and related conditions: Daily Activities, Walking, Handling Objects, Pain or Discomfort, and Feelings. Based on conceptual criteria and pilot testing, 219 items were selected for further testing. A questionnaire was mailed to patients from two hospital-based clinics and a stratified random community sample. Dimensionality of the domains was assessed through factor analysis. Items were analyzed with the Generalized Partial Credit Model as implemented in Parscale. We used graphical methods and a chi-square test to assess item fit. Differential item functioning was investigated using logistic regression.ResultsData were obtained from 888 individuals with arthritis. The five domains were sufficiently unidimensional for an IRT-based analysis. Thirty-one items were deleted due to lack of fit or differential item functioning. Daily Activities had the narrowest range for the item location parameter (-2.24 to 0.55) and Handling Objects had the widest range (-1.70 to 2.27). The mean (median) slope parameter for the items ranged from 1.15 (1.07) in Feelings to 1.73 (1.75) in Walking. The final item banks are comprised of 31–45 items each.ConclusionWe have developed IRT-based item banks to measure HRQL in 5 domains relevant to arthritis. The items in the final item banks provide adequate psychometric information for a wide range of functional levels in each domain.

Stressful experiences in childhood and chronic back pain in the general population.

Objectives:To determine if stressful experiences in childhood are associated with an increased risk of chronic back problems later in life. Methods:We conducted a prospective cohort study in the Canadian household population. Study participants were respondents to the first 3 cycles of the National Population Health Survey in Canada who were 18 years of age or older at baseline (n = 9552). Cases of chronic back pain during a 4-year follow-up period were ascertained with an interviewer-administered questionnaire. Stressful experiences in childhood were measured by an index consisting of 7 questions. Results:In multivariate analyses, the risk of back pain was 1.17 (95% confidence interval 0.97-1.41) for 1 stressful event and 1.49 (95% confidence interval 1.21-1.84) for 2 or more events. The effect was consistent across subgroups defined by gender, socioeconomic status, and health status. Specific events associated with an increased risk included fearful experiences, prolonged hospitalization, and parental unemployment. Discussion:Our study shows that persons reporting multiple stressful experiences in childhood are at increased risk of developing chronic back problems.

The risk of deep venous thrombosis and pulmonary embolism in giant cell arteritis: a general population-based study

Importance Patients with giant cell arteritis (GCA) may have an increased risk of pulmonary embolism (PE), similar to other systemic vasculitidies; however, no relevant population data are available to date. Objective To evaluate the future risk and time trends of new venous thromboembolism (VTE) in individuals with incident GCA at the general population level. Design Observational cohort study. Setting General population of British Columbia. Participants 909 patients with incident GCA and 9288 age-matched, sex-matched and entry-time-matched control patients without a history of VTE. Main outcome measures We calculated incidence rate ratios (IRR) overall, and stratified by GCA duration. We calculated HR of PE and deep vein thrombosis (DVT), adjusting for potential VTE risk factors. Results Among 909 individuals with GCA (mean age 76 years, 73% women), 18 developed PE and 20 developed DVT. Incidence rates (IR) of VTE, PE and DVT were 13.3, 7.7 and 8.5 per 1000 person-years (PY) in GCA cohort, versus 3.7, 1.9 and 2.2 per 1000 PY in the comparison cohort. The corresponding IRRs (95% CI) for VTE, PE and DVT were 3.58 (2.33 to 5.34), 3.98 (2.22 to 6.81) and 3.82 (2.21 to 6.34) with the highest IRR observed in the first year of GCA diagnosis (7.03, 7.23 and 7.85, respectively). Corresponding fully adjusted HRs (95% CI) were 2.49 (1.45 to 4.30), 2.71 (1.32 to 5.56) and 2.78 (1.39 to 5.54). Conclusions and significance These findings provide general population-based evidence that patients with GCA have an increased risk of VTE, calling for increased vigilance in preventing this serious, but preventable complication, especially within months after GCA diagnosis.

Effect of sociodemographic factors on surgical consultations and hip or knee replacements among patients with osteoarthritis in British Columbia, Canada.

Objective. To quantify the effect of demographic variables and socioeconomic status (SES) on surgical consultation and total joint arthroplasty (TJA) rates among patients with osteoarthritis (OA), using population-based administrative data. Methods. A cohort study was conducted in British Columbia using population data from 1991 to 2004. From April 1996 to March 1998, we documented 34,420 new patients with OA and these patients were followed to March 2004 for their first surgical consultation and TJA. Effects of age, sex, and SES were evaluated by Cox proportional hazards models after adjusting for comorbidities and pain medication used. Results. During a mean 5.5-year followup period, 7475 patients with OA had their first surgical consultations and 2814 patients received TJA within a 6-year mean followup period. Crude hazards ratio (HR) for men compared to women was 1.25 (95% CI 1.20–1.31) for surgical consultation and was 1.14 (95% CI 1.06–1.23) for TJA. The interaction between sex and SES was significant. Stratified analysis showed among men an HR of 1.42 (95% CI 1.27–1.58) and 1.52 (95% CI 1.26–1.83) for surgical consultations and TJA, respectively, for the highest SES compared with the lowest SES quintiles. Similarly significant results were observed among women. Conclusion. Differential access to the healthcare system exists among patients with OA. Women with OA were less likely than men to see an orthopedic surgeon as well as to obtain TJA. Patients with higher SES consulted orthopedic surgeons more frequently and received more TJA than those with the lowest SES.

Development of a population-based microsimulation model of osteoarthritis in Canada

OBJECTIVES The purpose of the study was to develop a population-based simulation model of osteoarthritis (OA) in Canada that can be used to quantify the future health and economic burden of OA under a range of scenarios for changes in the OA risk factors and treatments. In this article we describe the overall structure of the model, sources of data, derivation of key input parameters for the epidemiological component of the model, and preliminary validation studies. DESIGN We used the Population Health Model (POHEM) platform to develop a stochastic continuous-time microsimulation model of physician-diagnosed OA. Incidence rates were calibrated to agree with administrative data for the province of British Columbia, Canada. The effect of obesity on OA incidence and the impact of OA on health-related quality of life (HRQL) were modeled using Canadian national surveys. RESULTS Incidence rates of OA in the model increase approximately linearly with age in both sexes between the ages of 50 and 80 and plateau in the very old. In those aged 50+, the rates are substantially higher in women. At baseline, the prevalence of OA is 11.5%, 13.6% in women and 9.3% in men. The OA hazard ratios for obesity are 2.0 in women and 1.7 in men. The effect of OA diagnosis on HRQL, as measured by the Health Utilities Index Mark 3 (HUI3), is to reduce it by 0.10 in women and 0.14 in men. CONCLUSIONS We describe the development of the first population-based microsimulation model of OA. Strengths of this model include the use of large population databases to derive the key parameters and the application of modern microsimulation technology. Limitations of the model reflect the limitations of administrative and survey data and gaps in the epidemiological and HRQL literature.

Natural history of cartilage damage and osteoarthritis progression on magnetic resonance imaging in a population-based cohort with knee pain.

OBJECTIVES To determine the natural history of cartilage damage and of osteoarthritis (OA) progression using magnetic resonance imaging (MRI); to evaluate whether OA progression varies by stage of disease. METHODS A population-based cohort with knee pain was assessed clinically, with X-ray (Kellgren-Lawrence [KL] grading) and MRI. Cartilage was graded 0-3 on six joint surfaces. Frequency of cartilage damage change was determined for each joint site. Progression of OA was defined as a worsening of MRI cartilage damage by ≥1 grade in at least two joint sites or ≥2 grades in at least one joint site. The association of KL grade with OA progression was evaluated using parametric lifetime regression analysis. RESULTS 163 subjects were assessed at baseline and follow-up (mean 3.2 years). KL grade ≥2 was present in 39.4% at baseline. An increase in cartilage damage by ≥1 grade was seen in 8.0-14.1% of subjects at different joint sites. OA progression on MRI was present in 15.5%. Baseline KL grade was a significant predictor of OA progression with hazard ratio (HR) of 6.5 (95% confidence interval [CI] 1.4-30.7), 6.1 (95% CI 1.3-28.9), and 9.2 (95% CI 1.9-44.9) for KL grades 1, 2 and ≥3, respectively. CONCLUSION A low OA progression rate was seen over 3 years in this population-based symptomatic cohort. Radiographic severity, including KL grade 1, was a significant predictor of OA progression. Future interventions aimed at reducing progression will need to target not only radiographic OA, but also those with early abnormalities suggestive of pre-radiographic OA.