Background/Purpose:   There are no estimates of the prevalence of giant cell arteritis (GCA) or polymyalgia rheumatic (PMR) in a United States population in the current millennium. The purpose of this work was to estimate the 2015 point prevalence of GCA and PMR in a population-based study performed in a US population.

Methods:   Study populations of incident cases of GCA in 1950-2009 and incidence cases of PMR in 1970-2014 were previously identified among residents of a well-characterized geographically defined area. Prevalence estimates were obtained from the incidence rates assuming no increased mortality associated with GCA or PMR, which has been previously shown, and assuming migration in and out of the geographically defined area was independent of disease status. Age, sex and calendar year specific indigence rates and population lifetables were used to derive prevalence estimates. Prevalence estimates were age- and sex-adjusted to US white 2010 population aged ≥50 years. Bootstrap sampling was used to obtain 95% confidence intervals [CI] for the prevalence estimates.

Results:   A total of 248 incident cases of GCA were diagnosed in 1950-2009 and 790 cases of PMR were diagnosed in 1970-2014. The overall age and sex adjusted prevalence rate of GCA on January 1, 2015 was 204 (95% CI: 161, 254) per 100,000 population aged 50 years and older. The prevalence rate of GCA among women was 304 (95% CI: 229, 375) per 100,000 population aged 50 years and older and among men was 91 (95% CI: 46, 156) per 100,000 population aged 50 years. The overall age and sex adjusted prevalence rate of PMR on January 1, 2015 was 744 (95% CI: 694, 793) per 100,000 population aged 50 years and older. The prevalence rate of GCA among women was 907 (95% CI: 824, 994) per 100,000 population aged 50 years and older and among men was 557 (95% CI: 475, 638) per 100,000 population aged 50 years.

Conclusion:   Prevalence rates of GCA and PMR in the new millennium to 2015 are similar to previously published prevalence estimates in the late 1990s. For GCA this reflects the fact that the incidence of GCA has been stable for the past 20 years. For PMR there have been slight increases in incidence of PMR in recent years, which have not yet affected the prevalence of PMR, but may lead to future increases in the prevalence of PMR. The health burden of these diseases among older persons continues to be substantial and reflects the need for continued efforts to better manage it.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/contemporary-prevalence-estimates-for-giant-cell-arteritis-and-polymyalgia-rheumatica-2015/