Swain, Subhashisa
(2021)
Epidemiology of osteoarthritis and associated comorbidities in the United Kingdom.
PhD thesis, University of Nottingham.
Abstract
Background
Osteoarthritis (OA) is very common and is the main cause of chronic joint pain and disability in older people. According to this systematic review nearly 67% of people with OA had comorbidity. There is little information available on how the incidence and prevalence of OA has changed over the past 20 years in the UK, and what is the likelihood of having other chronic conditions, their progression, and associated outcomes.
Objectives
This research aimed to answer five questions: 1) how common is osteoarthritis in the UK and what are the trends over the past twenty years; 2) are people with osteoarthritis more likely to have other chronic conditions and multimorbidity (two or more conditions in an individual)than people without osteoarthritis; 3) in people with OA how do these long-term conditions coexist; 4) how does the group of long-term conditions progress with time; and 5) does the presence of long-term conditions in osteoarthritis add to the burden both to patients and to health services.
Methods
A large nationally representative UK primary care database known as the Clinical Practice Research Datalink(CPRD)GOLD was used for the study. Six different studies were performed in this thesis in people aged 20 years or more with OA and age, sex, and practice matched controls. These are:1) epidemiology of osteoarthritis in the UK (chapter 3); 2) risk of comorbidities occurring before and after the diagnosis of osteoarthritis using both case-control and cohort design(chapter 4); 3) clusters of multimorbidity in people with OA and controls using latent class analysis (chapter 5); 4) illness pathways (transition and trajectories) of multimorbidity clusters in people with OA and controls using latent transition analysis and latent class growth analysis, respectively (chapter 6 and 7); 5) outcomes such as all-cause mortality, outpatient visits, inpatient admission and disability adjusted life years (DALYs) associated with OA and their comorbidities (chapter 8).
Results
The prevalence of OA in the UK primary care in 2017 was 10.7% and the incidence was 6.8 per 1000 person-years in people aged 20 and over. OA was more common in women compared to men and increased with age, especially after age 40 years. The prevalence has increased at a rate of 1.4% per year since 1998, whereas the incidence is declining at a rate of -1.6% per year. The burden of joint pain defined as OA is quite high, constituting nearly one third of primary care adult patients.
People with OA are more likely to have multimorbidity prior to (aOR1.71, 95%CI1.69-1.74) and after the diagnosis of OA (aHR1.29, 95%CI1.28-1.30) than people without OA. Musculoskeletal (MSK), gastrointestinal (GI), cardiovascular (CV) and psychological conditions were associated with OA before and after the diagnosis of OA, whereas dementia and systemic lupus erythematous (SLE)were only associated with OA after its diagnosis. Other conditions that showed significant associations with OA both before and after diagnosis, were anaemia, inflammatory bowel disease (IBD), benign prostatic hypertrophy (BPH), gall stones, liver diseases, cancer, and hearing impairment.
Five multimorbidity clusters were identified in OA. These clusters were led by both pain and hypertension, hypertension only, depression, back pain only, and relative healthy group (lowest number of any conditions).
Over time, comorbidity clusters changed after the diagnosis of OA. About 30% of people changed from the cluster driven by either back pain or hypertension to the cluster driven by both back pain and hypertension. The accumulation of multimorbidity in people with OA happens in five different ways, and 17.5% of people develop multimorbidity quicker compared to relative healthy group. Obesity, smoking and alcohol use during the diagnosis of OA are strongly associated with the faster development of multimorbidity.
People with OA were 1.2 times more likely to consult with general practitioners (GP),1.1 times more likely to be hospitalised, 3.25 times likely to get higher DALYs and 1.9 times more likely to die. Within OA, people with multimorbidity had higher mortality, burden, and health utilisations.
Conclusions
OA affects one in ten people aged 20 years or more in the UK. The burden of both GP diagnosed OA and joint pain in primary care is consistently high and increasing further. People with OA are more likely to develop other chronic conditions. Five different comorbidity clusters have been identified. While younger people are likely to have pain and depression, the elderly are likely to have CV-MSK comorbidities. The growth of multimorbidity in people with OA differs with 17.5% developing it faster than others. People with OA and CV-MSK and CV comorbidity have worse health outcomes. This information from this study can be used to develop personalised care in primary care. Further research is needed to understand the causality between OA and comorbidity.
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