RESEARCH - Mortality trends in RA: the role of RF

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J Rheumatol. 2008 Apr 15

Mortality Trends in Rheumatoid Arthritis: The Role of Rheumatoid Factor.

A, Icen M, Kremers HM, Crowson CS, JM 3rd, Therneau TM,

VL, SE.

From the Department of Internal Medicine, Caritas St. 's

Medical Center, Boston, Massachusetts; Division of Epidemiology and

Biostatistics, Department of Health Sciences Research; Division of

Rheumatology, and Division of Cardiovascular Diseases, Department of

Medicine, Mayo Clinic, Rochester, Minnesota, USA.

OBJECTIVE: We previously demonstrated a widening in the mortality gap

between subjects with rheumatoid arthritis (RA) and the general

population. We examined the contribution of rheumatoid factor (RF)

positivity on overall mortality trends and cause-specific mortality.

METHODS: A population-based RA incidence cohort (1955-1995, and aged

>= 18 yrs) was followed longitudinally until death or January 1, 2006.

The underlying cause of death as coded from national mortality

statistics and grouped according to ICD-9/10 chapters was used to

define cause-specific mortality. Expected cause-specific mortality

rates were estimated by applying the age-, sex-, and

calendar-year-specific mortality rates from the general population to

the RA cohort. Poisson regression was used to model the observed

overall and cause-specific mortality rates according to RF status,

accounting for age, sex, disease duration, and calendar year. RESULTS:

A cohort of 603 subjects (73% female; mean age 58 yrs) with RA was

followed for a mean of 16 years, during which 398 died. Estimated

survival at 30 years after RA incidence was 26.0% in RF+ RA subjects

compared to 36.0% expected (p < 0.001), while in RF- RA subjects,

estimated survival was 29.1% compared to 28.3% expected (p = 0.9). The

difference between the observed and the expected mortality in the RF+

RA subjects increased over time, resulting in a widening of the

mortality gap, while among RF- RA subjects, observed mortality was

very similar to the expected mortality over the entire time period.

Among RF+ RA subjects, cause-specific mortality was higher than

expected for cardiovascular [relative risk (RR) 1.50; 95% confidence

interval (CI) 1.22, 1.83] and respiratory diseases [RR 3.49; 95% CI

2.51, 4.72]. Among RF- RA subjects, no significant differences were

found between observed and expected cause-specific mortality.

CONCLUSION: The widening in the mortality gap between RA subjects and

the general population is confined to RF+ RA subjects and largely

driven by cardiovascular and respiratory deaths.

PMID: 18412312

http://www.ncbi.nlm.nih.gov/pubmed/18412312

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