Incidence and disease course of polymyalgia rheumatica during two decades: a nationwide study across healthcare sectors in Denmark

OBJECTIVE: A new algorithm enables the identification of patients with polymyalgia rheumatica (PMR) across healthcare sectors in Denmark. We estimated annual incidence rates from 2003 to 2024 and described the disease course, including the occurrence of late-onset GCA and prednisolone (PDN) treatment. METHODS: A Danish nationwide, population-based cohort study was conducted using data linked at the individual level. Cases were identified among persons aged 50 or older between 1 January 2003 and 1 November 2024. RESULTS: A total of 51,401 patients were identified, including 24,456 from primary care and 26,945 from secondary care. The age-standardised incidence of PMR was 112 per 100,000 people (95% CI: 110.8-112.8). During the study period, the incidence declined by 53% in primary healthcare and increased by 30% in secondary healthcare, resulting in an overall decline of 12%. Among patients with PMR, GCA occurred at a rate of 5.4 (95% CI: 5.1-5.7) per 1,000 patient-years, with a median of 68 days (IQR [10-602]) from PMR diagnosis. Overall, 28% and 22% of patients were still treated with PDN after five and ten years, with a median daily dose of 4.1 and 5.5 mg of PDN, respectively. CONCLUSION: The increasing incidence of PMR in secondary healthcare was exceeded by the declining incidence in primary healthcare. Most late-onset GCA developed within the first year after PMR diagnosis. Many patients continued treatment with PDN for five to ten years, indicating a need for earlier use of concomitant therapies.