PsA incidence rising 3% annually among women in US, overall incidence remains steady
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Although the overall incidence of psoriatic arthritis in the United States remained stable from 2000 to 2017, there was a 3% per-year increase among women during this time, according to data published in Arthritis & Rheumatology.
“There are few population-based studies on the epidemiology of psoriatic arthritis, and temporal trends in the incidence of PsA in the United States are unclear,” Paras Karmacharya, MBBS, MS, of the Mayo Clinic, in Rochester, Minnesota, told Healio Rheumatology. “Among the available studies, there is significant variability in the reported prevalence and incidence rates of PsA, which may be related to how PsA is defined in the studies. While the lowest estimates were derived from studies using administrative codes to identify PsA cases, the highest prevalence was described in studies that used self-reported diagnosis of PsA.”
To analyze the incidence of PsA in the United States and examine incidence and mortality trends over the past 50 years, Karmacharya and colleagues conducted a retrospective, population-based study of residents of Olmsted County, Minnesota, using data from the Rochester Epidemiology Project. According to the researchers, the population of Olmsted County, which includes Rochester, in 2010 was 144,248, of whom 74.7% were adults. Medical records for all residents who sought care over the past 5 decades are available for all providers in the area, including the Mayo Clinic, through a linkage system.
The researchers used ICD-9 and ICD-10 diagnostic codes for arthralgias, arthritis, monoarthritis, oligoarthritis, polyarthritis, spondylitis, ankylosing spondylitis, arthropathy, psoriatic arthropathy, spondyloarthropathy and seronegative spondyloarthropathy to screen for patients with PsA. They then performed medical record reviews of all potential cases from Jan. 1, 2000, to Dec. 31, 2017. PsA cases were defined as adults who met the Classification of Psoriatic Arthritis (CASPAR) criteria — the same criteria used with a previously reported cohort from 1970 to 1999.
Questionable cases resolved by mutual agreement between the researchers. All patients were followed until Dec. 31, 2019. The researchers reported age- and sex-specific incidence rates and point prevalence, adjusted to the U.S. white population in 2010.
According to the researchers, there were 164 incident cases of PsA from 2000 to 2017. The overall age‐ and sex‐adjusted annual incidence of PsA during this period was 8.5 per 100,000 (95% CI, 7.2-9.8), with a higher rate in men (9.3; 95% CI, 7.4‐11.3) compared with women (7.7; 95% CI, 5.9‐9.4). Overall incidence was highest among those aged 40 to 59 years.
Although incidence rate was relatively stable from 2000 to 2017 — both overall and in men — there was an increase of 3% per year in women, compared to the period from 1970 to 1999, which saw a 4% per year rise in incidence. Meanwhile, point prevalence was 181.8 per 100,000 (95% CI, 156.5‐207.1) in 2015. In addition, the percentage of women among patients with PsA increased from 39% during the 1970‐1999 period to 41% during 2000‐2009 and 54% in 2010‐2017 (P = .08). Overall survival among patients with PsA did not differ from the general population (SMR = 0.85; 95% CI, 0.61‐1.15).
“Our study provides a good picture of the epidemiology of PsA in the population-based setting of Olmsted County, Minnesota,” Karmacharya said. “Knowing the recent epidemiology of PsA will help predict the actual burden of disease in the United States and allocation of resources. Our study also shows that, unlike in the clinical trial setting where the disease is mostly polyarticular, PsA has a highly heterogeneous presentation in the general population. In our PsA cohort, there was predominantly asymmetric joint involvement, and distal interphalangeal joint involvement was seen in 32% of patients.
“A total of 30% of patients had enthesopathy, 44% dactylitis, and 11% had inflammatory back pain at or before the diagnosis of PsA,” he added. “The most common sites of enthesopathy were plantar fascia, lateral epicondyle and Achilles tendon. A few patients presented with enthesopathy at multiple sites. The majority of patients had psoriasis at diagnosis, or a personal history of psoriasis, or a family history of psoriasis. Radiographic damage was common and noted in 30% of patients. Therefore, we need an individualized therapy approach according to the predominant domain involvement and their clinical presentation.”
Perspective
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David A. McLain, MD, MACR, FACP, FRCP
This is an Olmstead County Study of Psoriatic Arthritis based on the Rochester Epidemiology Project (The REP). I was recently talking in the office about what a small world this is. The REP was the creation of Leonard T. Kurland, MD, in 1963, a neurologist and close friend of my father-in-law. Kurland envisioned the population-based data resource that would result from combining the clinical documentation developed by the Mayo Clinic with that obtained by other community providers, most notably the Olmsted Medical Group and its affiliated Olmsted Community Hospital.
The REP is able to provide accurate incidence data for almost any serious condition and to support population-based analytic studies of disease causes and outcomes. Why is Olmstead County so unique for these epidemiologic studies in the United States and the world? Olmstead County is isolated from other urban centers and is tied to a major medical center with an extensive medical record system of in-patient and out-patient visits preserved since the turn of the 20th century.
Henry Stanley Plummer, MD, a Mayo Clinic doctor, revolutionized medical record keeping in 1907 and this is said to be one of the biggest contributions to medicine from the Mayo Clinic. The location of the Mayo Clinic itself is unique. The unexpected location of the world’s largest private practice of medicine — amid cornfields in the rural Midwest — has its roots in the War Between the States when William W. Mayo, MD, moved to Rochester to become examining surgeon for the Enrollment Board, a Civil War induction center.
After a tornado in 1883, the Sisters of St. Francis built St. Mary’s Hospital on the condition that Dr. Mayo and his sons (William J. Mayo, MD, and Charles H. Mayo, MD) provide medical care. Later, in 1954, Rochester Methodist Hospital was built. The medical records of more than 5 million patients who have ever been examined at Mayo Clinic Rochester are maintained in a central repository and tracked by computerized bar code. The providers with REP, per one study, were seeing 83% of residents of Olmstead County and responsible for 96% of the elderly hospital admissions. More than 3,000 publications have been written based on “The REP” — here is another one.
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