January 08, 2020
2 min read

Multimorbidity accumulation in RA accounts for excess mortality

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Kazuki Yoshida

The accumulation of multimorbidity following a rheumatoid arthritis diagnosis can account for excess total and cardiovascular mortality among women, according to data published in Arthritis Care & Research.

“Increased risk of death, as well as increased comorbidity burden among rheumatoid arthritis patients have been known,” Kazuki Yoshida, MD, ScD, of Brigham and Women’s Hospital, told Healio Rheumatology. “However, how the total burden of morbidities, or multimorbidity, accumulates over time since a new diagnosis of RA compared to non-RA comparator has not been well described, let alone its contribution to the increased mortality.”

To examine how multimorbidity following a diagnosis of RA, as well as lifestyle changes, impact excess mortality, Yoshida and colleagues conducted a matched cohort study of women in the Nurses’ Health Study. According to the researchers, this large cohort includes 121,700 female registered nurses in the United States, enrolled in 1976. Follow-ups have been conducted since then through mailed questionnaires sent every 2 years. Collected information included sociodemographics, anthropometrics, behaviors, treatments, diet and health conditions.

Among these participants, Yoshida and colleagues identified 1,007 women with incident RA, matched to 10,070 comparators without RA based on age and year. The researchers determined causes of death using death certificates and medical records. A Multimorbidity Weighted Index (MWI) used by the researchers included 61 chronic conditions. In addition, they used inverse probability weighting analysis to analyze the impact of postindex MWI and lifestyle factors on total, cardiovascular and respiratory mortality, comparing women with RA to those without.

The accumulation of multimorbidity following a RA diagnosis can account for excess total and cardiovascular mortality among women, according to data.
Source: Adobe

According to the researchers, after adjusting for baseline cofounders, patients with RA demonstrated higher risks for total (HR = 1.46; 95% CI, 1.32-1.62), cardiovascular (HR = 1.54; 95% CI, 1.22-1.94) and respiratory (HR = 2.75; 95% CI, 2.05-3.71) mortality, compared with those with RA. Adjusting for follow-up lifestyle factors — such as physical activity, BMI, diet and smoking — attenuated but did not substantially account for this excess mortality. However, after additional adjustments for follow-up MWI, patients with RA demonstrated HRs of 1.18 (95% CI, 1.05-1.32) for total, 1.19 (95% CI, 0.94-1.51) for cardiovascular and 1.93 (95% CI, 1.42-2.62) for respiratory mortality.

“We found multimorbidity as measured with a novel, extensive multimorbidity measure, Multimorbidity Weighted Index, increased more rapidly among RA patients,” Yoshida said. “This, in turn, accounted for major parts of increased all-cause and cardiovascular deaths. This underscores the importance and usefulness of the multimorbidity concept in RA management. The increased respiratory deaths, which was less accounted for MWI, may mean the need for extending the set of pulmonary morbid conditions in the MWI, currently only asthma and chronic obstructive pulmonary disease.”

“RA is a systemic inflammatory disease with implications beyond joints,” he added. “Its multimorbid nature requires rheumatologists and primary care providers to actively take part in monitoring for multimorbidity. What management strategies may be able to lessen the accumulation of multimorbidity and increased mortality is a remaining question.” – by Jason Laday

Disclosure: The researchers report funding from NIAMS and the NIH.