Abstract
Purpose (the aim of the study): Ostoearthritis (OA) is commonly comorbid with other long-term conditions (LTCs), increases the subsequent risk of developing comorbid LTCs, and exacerbates both the costs and the detriments of those LTCs. This study identified the excess health losses and excess health care consumption associated with OA with and without comorbid long-term conditions in Aotearoa New Zealand (AoNZ). Our two principal research questions were: 1) Is OA associated with excess health losses and health care consumption, and how do these impacts differ by ethnicity, socioeconomic status, and the presence of comorbid long-term health conditions?; 2) In people with OA, is the presence of comorbid chronic health condition(s) associated with excess health losses and health care consumption?
Methods: We used data from the NZ Health Survey (NZHS), a large representative survey of the health status, health behaviours, and health service utilisation of the NZ population conducted annually by Statistics NZ and the Ministry of Health (MoH). We pooled the 2011/12 to 2018/19 annual surveys. In the Statistics NZ Integrated Data Infrastructure (IDI) platform, NZHS data were linked with participants’ MoH health service use, at the individual level, to investigate participants’ comorbid health conditions, through pharmaceutical prescribing records and diagnoses recorded in hospital inpatient admissions, and calculate excess healthcare consumption in people with OA and comorbid conditions.
Baseline covariates and outcome measures were compared between the groups with and without OA and each of the comorbid conditions of interest. We tested the association of OA (among the full cohort and among those with and without each of the comorbidities) with each of the outcomes. Among those participants with OA, we tested the association of a) each index disease (reference: persons without the index disease) while adjusting for the presence of other diseases, and b) the number of diseases (reference: participants reporting no disease) with each outcome.
Results: For the first research question, we used the full cohort of 91,275 respondents to the NZHS, including the 11,184 with self-reported OA diagnosis and 80,091 without OA. Those with OA had substantially higher healthcare utilisation and public healthcare costs, greater unmet need for healthcare, lower levels of physical activity, higher mortality rates, and worse health-related quality of life.
After adjusting for baseline covariates, OA was significantly associated with increases in most of the healthcare utilisation outcomes considered, higher total public healthcare costs (mostly due to hospital costs associated with joint replacement surgery), obesity, comorbidity, and worse health-related quality of life. However, it was not significantly associated with physical activity levels, and was negatively associated with mortality rates. There was little difference in any of the incremental impacts of OA between those with and without each of the comorbidities considered.
Among people without self-reported OA, the majority (51.6%) had no recorded LTC. Among people with self-reported OA only 19.2% had no comorbidities, with a mean of 1.4 (sd 1.0) comorbidities. The most common comorbidity was CVD (66%), followed by mental health conditions (40%), respiratory disease (29%), and diabetes (15%). Healthcare utilisation and public healthcare costs were substantially higher among those with comorbidities, as was self-reported unmet need for healthcare. After adjusting for differences in baseline covariates between groups, all comorbidities were significantly associated with increased healthcare use and public healthcare costs, across all measures of healthcare use except for some OA-specific or musculoskeletal-focused healthcare (total joint replacements and visits to physiotherapists, chiropractors, and osteopaths). Comorbidities were significantly associated with reduced physical activity, increased mortality risk, and reduced quality of life (overall and physical health-related; no difference in mental-health related quality of life except for those with mental health comorbidities).
Conclusions: OA significantly impacts health-related quality of life, healthcare utilisation and total public healthcare costs, and a very high proportion of people with OA have multimorbidity. People with OA and comorbidities have higher risk of mortality, worse overall health-related quality of life, healthcare utilisation and public healthcare costs were substantially higher, and self-reported unmet need for healthcare was also higher. These findings have implications in regard to the value for money of public health policy and interventions targeting common causes of both OA and other long-term conditions.