Disability in rheumatoid arthritis has declined an average of 1.7% per year since the advent of disease-modifying antirheumatic drugs, especially methotrexate.
The finding justifies "continued emphasis on early and consistent [disease-modifying antirheumatic drugs (DMARDs)] use and the incorporation of biologicals into our therapeutic repertoire," wrote Dr. Eswar Krishnan in Annals of the Rheumatic Diseases, published online Sept. 27 (doi:10.1136/annrheumdis-2011-200354).
Dr. Krishnan of the division of rheumatology and immunology at Stanford (Calif.) University and his colleagues looked at 4,651 adult patients from ARAMIS (Arthritis, Rheumatism, and Aging Medical Information System), a national longitudinal database. Most (76%) were female, and nearly all (88%) were white.
All patients were mailed a health assessment questionnaire (HAQ) at 6-month intervals, beginning in 1983 through 2006, which assessed disability on a scale of 0-3, with 3 being the worst, in eight areas: dressing/grooming, arising, eating, walking, hygiene, reach, grip, and activities. An average overall score was obtained for each patient by summing all scores and dividing by 8.
Overall, a mean of 13 semiannual assessments were completed during the study period per patient.
Dr. Krishnan found that the average HAQ-disability score improved from 1.3 in the 1980s, to 1.2 in the 1990s, to 1.1 or lower in the 2000s.
The authors then divided up the study period into three defined eras. The first, from 1982 to 1990, represented the "NSAID-based" era, when nonsteroidal anti-inflammatory drug treatment was the primary therapy for RA. The second era, from 1991 to 2000, they called the "methotrexate/DMARD" era, when these agents dominated treatments.
The final period, from 2001 to 2006, was deemed the "methotrexate and biologic DMARD period," when combination therapy with biologic and nonbiologic agents became the norm.
When thus divided and plotted on a graph using least-squares regression, wrote the authors, the trend lines showed that disability remained relatively constant over the NSAID-based era (prior to 1990), then declined significantly (P = .001) in the nonbiologic (methotrexate) era (1992-1997) and in the biologic and nonbiologic era (P less than .01).
Moreover, wrote the authors, "the composition of our cohort changed over time in a way that can [be] expected to increase disability over time," including an increasing average age (57.2 years in 1983, vs. 64.3 years in 2006) and disease duration (a mean of 14.4 years at cohort inception to 24.1 years in 200).
"Thus, the estimated declines in RA disability in the biological era are likely to be an underestimate of the true declines," they added.
"Our finding supports the prevailing notion that ‘tight inflammation control’ is a desirable therapeutic strategy," they concluded.
Dr. Krishnan postulated that changing drug therapies were not the only contributors to decreasing disability over time.
For one, smoking prevalence declined from a high of 27.9% to just 5% among the study participants between 1992 and 2006, reported the authors.
"Another relevant trend has been the setting of more stringent targets for RA treatment success, such as ‘remission’ or ‘low disease activity,’ which perhaps leads to an earlier escalation to more aggressive treatment regimes," they added.
Finally, the authors pointed out that an "ongoing national secular decline in disability" may have resulted in a decrease of comorbid heart disease, chronic obstructive pulmonary disease, and stroke, conditions that could exacerbate disability in this population.
The authors disclosed that Centocor Ortho-Biotech, a maker of biologic RA drugs, funded the study. They disclosed no additional individual competing interests.