OP0054 REDUCING THE BURDEN OF LOW BACK PAIN: RESULTS FROM A NEW MICROSIMULATION MODEL

Background

Low back pain (LBP) has been the leading cause of disability worldwide for the past 30 years. In 2019, LBP was responsible for 64 million years lived with disability (YLDs) [1].

Objectives

The purpose of the present study was to project and compare the impact of three strategies for reducing the population health burden of LBP: weight loss, ergonomic interventions, and an exercise program.

Methods

We have developed a microsimulation model of LBP in Canada using a novel simulation platform, SimYouLate. The initial population was derived from Cycle 1 (2001) of the Canadian Community Health Survey (CCHS). We modeled an open population 20 years of age and older. Key variables included age, sex, education, body mass index (BMI), type of work, having a back problem, pain level in persons with back problems, and exercise. The effects of interventions on the risk of LBP were obtained from the CCHS for the effect of BMI, the Global Burden of Disease Study for occupational risks, and a published meta-analysis for the effect of exercise. All interventions lasted from 2021 to 2040. Strength of the interventions varied over a wide range. YLDs were defined as LBP prevalence multiplied by disability weight. The population health impact of the interventions was calculated as a difference in YLDs between the base-case scenario and each intervention scenario and expressed as YLDs averted per intervention unit and as % of total LBP-related YLDs.

Results

In the base-case scenario, LBP in 2020 was responsible for 424,900 YLDs in Canada and the amount increased to 460,312 YLDs in 2040. The effects of the interventions on YLDs were as follows: 27,993 (95% CI 23,373, 32,614) YLDs averted over 20 years per 0.1 unit change in log-transformed BMI (10.5% change in BMI) among overweight and obese individuals, 19,416 (16,275, 22,557) YLDs averted per 1% reduction in the proportion of workers exposed to occupational risks, and 26,058 (22,455, 29,661) YLDs averted per 1% increase in the proportion of eligible patients with back problems participating in the exercise program. Table 1 shows the intervention impact as % of total LBP-related YLDs and Figure 1 shows YLD-equivalence between the interventions. A one unit reduction in BMI per year among the overweight and obese individuals would be approximately equivalent in terms of disability reduction to an effective ergonomic intervention in 35% of at-risk workers and an exercise intervention in 27% of eligible patients with back problems over the same period (Figure 1).

Table 1.

YLDs averted between 2021 and 2040 as % of total LBP-related YLDs, according to intervention type and level, in persons aged 20+ in Canada

InterventionEffect (%)95% LCL95% UCLReduction in BMI per year0.11.4-1.44.10.34.82.27.30.56.33.98.81.08.56.011.03.011.99.414.45.013.510.916.0Reduction in occupational exposure20%5.21.98.540%9.56.412.760%13.810.616.980%18.114.821.4100%22.418.825.9Increase in exercise participation20%6.62.810.440%12.48.716.060%18.114.521.780%23.920.127.6100%29.625.533.7

LCL: lower confidence limit. UCL: upper confidence limit.

Figure 1.

Equivalence between BMI, ergonomic and exercise interventions in terms of their impact on YLDs. Each point represents a specific number of YLDs averted. Values on the y-axis show reduction in % of workers at risk and increase in % exercising that are required to achieve the same reduction in YLDs as the corresponding reduction in BMI shown on the x-axis.

Conclusion

This is the first population-based microsimulation study to compare currently available preventive strategies in LBP in terms of YLDs averted and to provide measures of equivalence between these strategies.

References

[1]Hartvigsen J, Hancock MJ, Kongsted A, et al. What low back pain is and why we need to pay attention. Lancet 2018;391(10137):2356-2367.

Acknowledgements

The study was supported by a grant from the Canadian Institutes for Health Research (FRN 142440).

Disclosure of Interests

None declared.

Patterns of medication use before, during and after pregnancy in women with systemic lupus erythematosus: a population-based cohort study

Objectives

This study aimed to characterize the patterns of medication use before, during and after pregnancy in a population-based cohort of women with systemic lupus erythematosus (SLE).

Methods

Using population-based administrative data in British Columbia, Canada, with valid information on start date of pregnancy, we identified women with SLE who had singleton pregnancies ending in deliveries between January 1, 2002, and December 31, 2012. We assessed the proportion of SLE pregnancies exposed to SLE medications – namely antimalarials and immunosuppressants – as well as glucocorticosteroids, and nonsteroidal anti-inflammatory drugs (NSAIDs) 24 months before pregnancy, each trimester of pregnancy, and 12 months postpregnancy. We also assessed discontinuation of antimalarials and immunosuppressants, defined as no prescriptions in a given window following a prescription in a preceding window.

Results

Of 376 pregnancies (284 women) with SLE, 24.2% had one or more dispensing for antimalarials, 8.2% for azathioprine, 19.7% for glucocorticosteroids and 4.8% for NSAIDs during pregnancy. We observed a 16.7% discontinuation of antimalarials in the year prior to pregnancy, 29.8% in the first trimester, 9.7% in the second trimester, and 26.0% in the third trimester. We also observed a 29.2% discontinuation of azathioprine in the first trimester, 8.0% in the second trimester, and 9.1% in the third trimester.

Conclusions

These population-based data show frequent discontinuation of medications, particularly antimalarials, in SLE pregnancies. These findings suggest the importance of educating women with SLE who are pregnant or planning to become pregnant on the benefits and risks of medications during pregnancy.

Relationship between physical activity and hip pain in persons with and without cam or pincer morphology: a population-based case-control study

OBJECTIVES

The purpose of the study was to determine if physical activity (PA) is a risk factor for persistent or recurrent hip pain in young and middle-aged persons with and without radiographic findings of cam or pincer morphology (CPM).

METHODS

A population sample of persons aged 20-49 with (cases) and without (controls) hip pain in Metro Vancouver, Canada, was selected through random digit dialing (RDD). Self-reported PA was expressed as average energy expenditure (MET-hours) per year, over lifetime. CPM was defined as alpha angle >55°, lateral centre edge angle (LCE) >40°, or positive cross-over sign.

RESULTS

Data were obtained for 500 subjects, 269 cases and 231 controls. Prevalence of radiographic CPM was 49% in the cases and 44% in the controls. In a logistic regression model adjusted for age, gender and CPM, total lifetime PA, including occupational, domestic and recreational activities, was significantly associated with hip pain (Odds ratio (OR) 1.30 per 1000 MET-hours, 95% CI 1.15-1.38). The effect of total PA was observed in those with CPM (1.44, 1.17-1.78) and without CPM (1.23, 1.04-1.45). For domestic activities, the association was seen only in those with CPM (significant interaction). When PA was categorized into quartiles, higher levels of PA were associated with a greater risk of pain.

CONCLUSIONS

PA, as measured by average energy expenditure over lifetime is a risk factor for hip pain in young and middle-aged persons. For some activities, the risk is likely increased in persons with radiographic evidence of CPM.

The relationship between subchondral sclerosis detected with MRI and cartilage loss in a cohort of subjects with knee pain: the knee osteoarthritis progression (KOAP) study

PURPOSE

To assess the association between subchondral sclerosis detected at baseline with MRI and cartilage loss over time in the same region of the knee in a cohort of subjects with knee pain.

METHODS

163 subjects with knee pain participated in a longitudinal study to assess knee osteoarthritis progression (KOAP). Subjects received baseline knee radiographs as well as baseline and 3-year follow-up MRI examinations. Baseline subchondral sclerosis and bone marrow lesions (BMLs) were scored semiquantitatively on MRI in each region from 0 to 3. Cartilage morphology at baseline and follow-up was scored semiquantitatively from 0 to 4. The association between baseline subchondral sclerosis and cartilage loss in the same region of the knee was evaluated using logistic regression, adjusting the results for age, gender, body mass index, and the presence of concomitant BMLs.

RESULTS

The prevalence of subchondral sclerosis detected by MRI in the regions of the knee varied between 1.6% (trochlea) and 17% (medial tibia). The occurrence of cartilage loss over time in regions varied between 6% (lateral tibia) and 13.1% (medial femur). The prevalence of radiographically-detected subchondral sclerosis in compartments varied from 2.9% (patellofemoral) to 14.2% (medial tibiofemoral). In logistic regression models, there were no significant associations between baseline subchondral sclerosis detected by MRI and cartilage loss in the same region of the knee.

CONCLUSION

Baseline subchondral sclerosis as detected by MRI did not increase the risk of cartilage loss over time.

The association of magnetic resonance imaging (MRI)-detected structural pathology of the knee with crepitus in a population-based cohort with knee pain: the MoDEKO study

Osteoarthritis (OA) is the most common arthropathy of the knee joint(1). Symptoms reported by patients and signs noted during physical examination guide clinicians in identifying subjects with knee OA(2-4). Pain is one of the most important symptoms reported by subjects with knee OA(2,3). Although very common, pain is a non-specific symptom, related to pathology in several structures within the knee joint, and includes synovitis(5), subchondral bone marrow lesions(6), and joint effusion(7). Further, pain is a subjective symptom that cannot be directly measured or assessed during physical examination. Crepitus or crepitation in association with arthritis is defined as a crackling or grinding sound on joint movement with a sensation in the joint. Crepitus may occur with or without pain and is a common finding during physical examination in subjects with knee OA(2-4,8,9). It is not known whether crepitus is related to pathology in various structures within the knee. The aim of our study was to determine the cross-sectional associations of structural pathologies within the knee with crepitus in a population-based cohort with knee pain, using magnetic resonance imaging (MRI). Subjects with knee pain were recruited as a random population sample, with crepitus assessed in each compartment of the knee using a validated and standardized approach during physical examination(10). MRI of the knee was performed to assess cartilage morphology, meniscal morphology, osteophytes, cruciate ligaments, and collateral ligaments. For both compartment-specific and whole-knee analyses, a multiple logistic regression analysis was performed to assess the associations of MRI-detected structural pathology with crepitus, adjusting for potential confounders. Variables were selected by backwards elimination within each compartment and in the overall knee models, and only statistically significant variables remained in the "selected" models; remaining variables in these models are adjusted for each other. An increased risk for compartment-specific crepitus was associated with osteophytes at the patellofemoral (PF) and lateral tibiofemoral (LTF) joints. Crepitus was associated with osteophytes and medial collateral ligament (MCL) pathology at the medial tibiofemoral (MTF) compartment, but cartilage damage was negatively associated with crepitus at this compartment. In the selected whole-knee model, only meniscal tears were associated with an increased risk for general crepitus. Thus, it seems that crepitus may be associated with pathology in several internal structures.

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.

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.

Contrast sensitivity and visual hallucinations in patients referred to a low vision rehabilitation clinic

AIM

To examine the association of reported visual hallucinations and measured visual parameters in adult patients referred for low vision rehabilitation.

METHODS

All patients (N = 225) referred to a low vision rehabilitation clinic for a calendar year were asked a standardised question about symptoms of formed visual hallucinations. Best corrected visual acuity and contrast sensitivity using the Pelli-Robson chart were measured. We conducted multiple logistic regression analysis of the association between visual hallucinations and visual parameters.

RESULTS

Of the total cohort, 78 (35%) reported visual hallucinations. Visual acuity and contrast sensitivity were considered in four quartiles. In multiple logistic regression controlling for contrast sensitivity, age, gender, report of depression and independence, measured acuity in each of the poorer three categories (compared to the best) was not associated with reported hallucinations. Contrast sensitivity in the three poorer quartiles (compared to the best) was strongly associated with the report of hallucinations (OR 4.1, CI 1.1, 15.9; OR 10.5, CI 2.6, 42.1; OR 28.1, CI 5.6, 140.9) after controlling for acuity, age, sex, depression and independence.

CONCLUSIONS

Lowest contrast sensitivity was the strongest predictor of reported hallucinations after adjusting for visual acuity.