Background: Osteoarthritis (OA) is associated with increased comorbidity, but knowledge of the temporal relationships between OA and comorbidities is limited.

Objectives: To estimate the risk of consulting for comorbidities in people with incident clinician-diagnosed knee or hip OA.

Methods: Using the Swedish Population Register, we identified all residents aged 35 years or above in the Skåne region, Sweden (total pop. 1.23 million) in the year 2009. We used the Skåne Health Care Register (SHR), a comprehensive register based on physicians’ International Classification of Disease (ICD) 10, to identify persons who had at least one diagnosis of knee or hip OA – the exposures of interest – and 18 other diagnoses ( Figure 1 ) – the outcomes of interest – between 1 January 2010 and 31 December 2017. To minimize potential confounding due to propensity to seek care, persons had to have at least one health-care visit with any diagnosis registered between 1 January 1998 and 31 December 2009 to be included. We excluded persons with a knee or hip OA diagnosis before 1 January 2010, and for each analysis, persons with a previous diagnosis of the outcome diagnosis of interest. People were followed from 1 January 2010 until relocation outside of the region, death, outcome diagnosis, or 31 December 2017, whichever came first. We calculated hazard ratios (HR) of each outcome diagnosis using Cox proportional hazard models with incident knee and hip OA as time-varying exposure. Time from start of follow-up to the date of an OA diagnosis was treated as unexposed, while time from an OA diagnosis to the outcome diagnosis was treated as exposed. Models were adjusted for residential area, if born in Sweden, annual income, years of education, marital status, sex, and age (all retrieved from Statistics Sweden), and baseline conditions (i.e. the other outcome diseases of interest, and alcohol-related disorders) as registered in SHR before 1 January 2010.

Results: We included 548,681 persons in the Skåne population having at least one health-care visit during 1998 to 2009 and no doctor-diagnosed knee or hip OA. Of these, 36,465 persons consulted for knee OA and 14,477 for hip OA during the follow-up period ( Table 1 ). Persons with clinician-diagnosed incident knee or hip OA have 8-61% higher hazard of depression, cardiovascular diseases, back pain, and osteoporosis than persons without an OA diagnosis ( Fig. 1 ). Both knee and hip OA persons have increased risk of diabetes, however the 95% confidence interval excluded 1 only for knee OA ( Fig. 1 ). Also, only knee OA patients have an increased risk of fracture to the forearm. For the rest of the diagnoses, we found either no increased risk for knee or hip OA persons, or estimates with wide confidence intervals, excluding any clear interpretations of the direction or size of the effects.

Conclusion: Incident clinician-diagnosed knee and hip OA are associated with increased risk of consultation for depression, cardiovascular disease, back pain, osteoporosis, and diabetes. Results support previous findings for cardiovascular diseases and diabetes, however suggesting that the risk of diabetes is mainly associated with knee OA.

Acknowledgments: This study was supported by FOREUM.

Disclosure of Interests: Kenneth Pihl: None declared, Aleksandra Turkiewicz: None declared, Velocity Hughes: None declared, Weiya Zhang Consultant of: Grunenthal for advice on gout management, Speakers bureau: Bioiberica as an invited speaker for EULAR 2016 satellite symposium, S.M.A. Bierma-Zeinstra Consultant of: From 2015-2017 for Infirst Healthcare, in 2019 for Phizer (consultancy fees were paid to the university), Daniel Prieto-Alhambra Grant/research support from: Professor Prieto-Alhambra has received research Grants from AMGEN, UCB Biopharma and Les Laboratoires Servier, Consultant of: DPA’s department has received fees for consultancy services from UCB Biopharma, Speakers bureau: DPA’s department has received fees for speaker and advisory board membership services from Amgen, Martin Englund Consultant of: Advisory Board 1 day (2019) Pfizer (Tanezumab).