FROM ARTHRITIS & RHEUMATOLOGY
The prevalence of arthritis in the United States is much higher than current estimates indicate, especially among adults under 65 years of age, a study showed.
The higher prevalence can be largely attributed to “the previous underestimate of arthritis in adults between 18-64 years of age,” according to S. Reza Jafarzadeh, PhD , and David T. Felson , MD , both of Boston University. Using a new surveillance model, they estimated that 91.2 million adults in the United States (36.8%) had arthritis in 2015, compared with a previously reported national estimate of 54.4 million adults (22.7%). Of these, 61.1 million were between 18 and 64 years of age (Arthritis Rheumatol. 2017 Nov 27. doi: 10.1002/art.40355 ).
Using data from 33,672 respondents to the 2015 National Health Interview Survey , Dr. Jafarzadeh and Dr. Felson developed a Bayesian model to estimate arthritis prevalence. In addition to physician-diagnosed arthritis, the investigators also examined responses to questions about chronic joint symptoms (pain, aching, or stiffness), and duration of symptom onset.
Arthritis prevalence was 29.9% in men aged 18-64 years (95% probability interval, 23.4-42.3), 31.2% in women aged 18-64 years (95% PI, 25.8-44.1), 55.8% in men aged 65 years and older (95% PI, 49.9-70.4), and 68.7% in women aged 65 years and older (95% PI, 62.1-79.9), the authors reported.
Among respondents aged 18-64 years, 19.3% of men and 16.7% of women reported that they had chronic joint symptoms but no physician-diagnosed arthritis. Among those 65 years of age or older, 15.7% of men and 13.5% of women responded that they had chronic joint symptoms without physician-diagnosed arthritis.
Current methodology for estimating arthritis prevalence is based on a single survey question asking whether a health care provider has ever told the patient that he or she has arthritis, a method that has previously been shown to have a sensitivity of 68.8% in adults 65 years of age and older and 52.5% for those aged 45-64 years, Dr. Jafarzadeh and Dr. Felson reported. “Such a low sensitivity, especially in a younger population, where almost half of true arthritis cases are missed, results in substantial misclassification and underestimation of prevalence and would have a detrimental effect for planning and needs assessment,” the authors wrote.
The two additional questions on joint pain, aching, and stiffness that the investigators included in the study captured “a substantial (i.e., 65%-80%) fraction of the population with arthritis, who are between 18-64 years of age, but are misclassified as healthy by the doctor-diagnosed arthritis criterion due to low sensitivity,” they said.
The study authors also speculated that younger patients might be more likely to ignore symptoms or visit a doctor less often.
“Further studies are needed to evaluate potential changes in the specific causes of arthritis, especially among adults below the age of 65,” they concluded.
The study was supported by a grant from the National Institutes of Health. The investigators did not disclose any other conflicts of interest.
