WASHINGTON — Early functional disability is predictive of all-cause and cardiovascular mortality in patients with inflammatory polyarthritis, Dr. Tracey M. Farragher reported at the annual meeting of the American College of Rheumatology.
An association between early functional disability, as measured by the Health Assessment Questionnaire (HAQ), and later mortality has previously been noted. But whether the baseline HAQ score or the HAQ score at 1 year, at which time disease modifying antirheumatic drug (DMARD) therapy is likely to have been initiated, represents a more accurate predictor of mortality has not previously been investigated, according to Dr. Farragher of the University of Manchester (England).
But now, analysis of longitudinal data from the Norfolk (England) Arthritis Register has determined that HAQ score at 1 year is a stronger predictor of mortality, particularly from cardiovascular causes, than is baseline HAQ score.
The register enrolled 1,010 patients with new-onset inflammatory polyarthritis between 1990 and 1994. They were assessed at 1, 5, 7, and 10 years, with structured interviews and clinical examinations. Patients were stratified according to HAQ score as being less than 1 (none or mild disability), 1–2 (moderate disability), or greater than 2 (severe disability).
By 1 year, 40% of the patients had been treated with a DMARD, which was reflected in changes in HAQ scores: In the 590 patients in the group with the lowest HAQ scores, the median swollen and tender joint count was one at baseline and none at year 1. In the 331 in the moderate HAQ group, the median swollen and tender joint counts were 6 at baseline and 2 at year 1, and in the 89 in the severe HAQ group, these counts were 10.5 at baseline and 5 at year 1.
Mortality rates per 1,000 person-years were calculated according to HAQ scores, and information on numbers and causes of death was obtained by the Office for National Statistics. By the end of 10 years, 170 patients had died, 69 (41%) of cardiovascular causes, with the highest mortality rates in the severe HAQ group at both time points.
The increase in the all-cause mortality rate per unit increase in HAQ score was about 25% greater using the 1-year score rather than the baseline score, Dr. Farragher wrote in a poster session. The hazard ratio for all deaths at baseline was 1.32, compared with 1.61 at year 1. The corresponding numbers for cardiovascular deaths were 1.29 and 1.96.
The 1-year HAQ score is a marker of residual disease activity and, by implication, physical activity, which may account for its predictive capacity for cardiovascular disease and mortality, wrote Dr. Farragher and her colleagues (Ann. Rheum. Dis. 2006 Nov 7 [Epub doi:10.1136/ard.2006.056390]).
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