1Pfizer Inc, New York, NY, USA. 2Eli Lilly and Co, Indianapolis, IN, USA. 3Pfizer Inc, Surrey, United Kingdom
Purpose Chronic pain impacts approximately 100 million patients in the United States (US), accounting for an estimated $560 to $635 billion per year (2010 dollars) in direct and indirect health care costs, including workplace productivity. Osteoarthritis (OA) is one of the most common causes of chronic pain and a leading cause of disability in the US. Furthermore, increased pain severity in patients with OA is associated with a poorer overall health-related quality of life (HRQoL), increased healthcare resource utilization (HCRU) and costs.Using survey data of individuals with OA from the Kantar 2019 US National Health and Wellness Survey (NHWS), we have previously shown that respondents with moderate-to-severe pain due to OA had more comorbidities, a higher rate of obesity, lower work productivity (longer disability leave, greater activity and work productivity impairment, absenteeism and presenteeism) and decreased HRQoL than those with mild OA pain. However, the extent to which pain severity among patients with OA differentially affects treatment patterns and adherence to pain medications has yet to be addressed. The objective of this study was to compare treatment patterns, medication adherence and HCRU of respondents with mild vs moderate-to-severe OA pain in a real-word setting. Methods This cross-sectional, observational study assessed data from the NHWS (Jan 2019-Dec 2019); a self-reported, internet-based survey containing data from 74,994 respondents, representative of the US population. Potential respondents were primarily identified via opt-in online survey panels, with stratified random sampling to ensure representativeness of age and gender. Adults ≥18 years who responded to the NHWS with patient-reported physician-diagnosed OA were included in the study. Respondents who reported experience with OA pain were included in the pain module of this study (N=6,851). These respondents were excluded if they reported cancer pain, did not report OA pain, or reported that the only joint affected by OA was the back, shoulder or neck. Data were available for 5,836 respondents. Self-reported data were collected for OA pain severity, OA pain treatment, adherence to pain medication (current and past) and HCRU. Patients were stratified into OA pain severity cohorts based on responses to the Short Form-McGill Pain Questionnaire visual analog scale (SF-MPQ-VAS) (mild: 1-34, moderate: 35-74, severe: ≥75, moderate-to-severe: combination of moderate and severe cohorts). Respondents who had a pain score of 0 were excluded from the study. The type of OA pain medication prescribed, number of pain drugs received, duration (length of time) and frequency of medication (maximum number of days taken in prior month) taken by respondents were recorded. Adherence was assessed using the simple version of the Medication Adherence Rating Scale (MARS), for which respondents provided an estimate of how much (%) of their prescribed pain medication they had taken in the last 4 weeks. Medication satisfaction was measured using a Likert scale of 1-7, with a score of 1 being extremely dissatisfied and a score of 7 being extremely satisfied. HCRU was assessed by the presence or absence of a visit during the 6 months prior to the survey, as well as recording the number of outpatient visits, emergency room (ER) or urgent care visits, and all-cause hospitalizations. Total population and cohorts were analyzed using descriptive analyses. Univariate analysis was performed to examine differences in treatment patterns and HCRU between mild and moderate-to-severe OA pain respondents. Results Overall, 5,836 respondents were included and stratified into cohorts with mild (n=2,038) or moderate-to-severe (n=3,798) OA pain. The majority of respondents across both mild vs moderate-to-severe cohorts were ≥55 years (55-64 years: 26.2% vs 31.3%; ≥65 years: 56.6% vs 45.2%), white (86.6% vs 82.3%), female (57.3% vs 69.4%), and had knee OA (72.5% vs 79.5%), respectively. Most respondents had a body mass index (BMI) that classified them as overweight (BMI 25-29kg/m2: 34.5% vs 26.0%) or obese (BMI ≥30kg/m2: 40.5% vs 53.0%), (both P<0.0001) respectively. While approximately half of mild and moderate-to-severe respondents were retired (52.4% vs 47.0%), significantly more respondents with mild OA pain were employed full-time (21.0% vs 16.6%) and reported an income ≥$75,000 (42.1% vs 26.4%), (all P<0.0001) respectively. Compared with mild OA pain respondents, significantly more moderate-to-severe OA pain respondents had self-reported diagnoses of sleep disturbance (7.8% vs 16.4%), insomnia (12.2% vs 25.3%), depression (23.6% vs 41.6%) and general anxiety disorder (10.2% vs 19.1%), (all P<0.0001) respectively. Furthermore, frequency of daily OA and joint pain was higher for the moderate-to-severe OA pain cohort (P<0.0001). Compared to those with mild OA pain, moderate-to-severe OA pain respondents received a greater proportion of pain drugs overall (31.7% vs 92.4%), especially NSAIDs (8.7% vs 21.8%) and strong opioids (4.0% vs 15.2%), (all P<0.0001) respectively. The most commonly taken over-the-counter drugs by both cohorts included acetaminophen and ibuprofen; and more mild OA pain respondents took ibuprofen (35.0% vs 29.9%) and less took acetaminophen (32.2% vs 36.9%) than moderate-to-severe OA pain respondents (both P<0.01). Compared with mild OA pain respondents, those with moderate-to-severe OA pain took pain medication for longer (94.2 vs 106.8 months) and at a higher medication frequency (21.1 vs 22.7 days during prior month; P<0.05). However, moderate-to-severe OA respondents reported lower overall satisfaction with their pain medication (4.8) vs mild OA pain respondents (5.2; P<0.0001), specifically NSAIDs and opioids (P<0.0001). Despite this, moderate-to-severe OA pain respondents were more adherent to their pain medication (76.4%) than those with mild OA pain (65.2%; P<0.0001). HCRU analyses showed that the number of outpatient visits (94.3% vs 95.8%, p<0.05), ER visits (11.5% vs 18.9%, p<0.0001) and hospitalizations (8.1% vs 10.8%, p<0.01) 6 months prior to the survey were greater in the moderate-to-severe OA pain cohort vs the mild OA pain cohort. Conclusions This real-world study captured a large amount of information on the impact of pain severity in 5,836 respondents with OA and their current treatments. Compared with those with mild OA pain, respondents with moderate-to-severe OA pain received significantly more pain medication, more frequently and showed greater adherence; however, this cohort was also significantly more dissatisfied with their current pain medication. Comparisons across both cohorts showed that respondents with moderate-to-severe OA pain reported greater HCRU, including outpatient visits, ER visits and hospitalization 6 months prior to participation in the survey. While these data are limited to self-reported pain assessed cross-sectionally over the past 4 weeks and applied to self-reported medical history, these findings were consistent with other studies that assessed treated populations and may be expanded to understand the relationship of OA pain severity, HCRU and treatment patterns at a national level. Understanding the clinical and economic burden of patients with moderate-to-severe OA pain may help to direct future changes in clinical practice settings and inform stakeholders to provide effective pain treatment in patients with moderate-to-severe OA pain.