Respiratory diseases but not cardiovascular diseases are an important underlying cause of excess death in patients with rheumatoid arthritis, Australian research shows.

An analysis of data from 1,895 patients in the Australian Rheumatology Association Database (ARAD), compared observed versus expected survival in matched general population data.

The study found that after 20 years, mortality was modestly increased in RA participants compared to population controls (Standardised Mortality Ratio 1.49, 95% CI 1.30.1.71, p < 0.001).

Survival in RA patients at 20 years was 79.1% compared to an expected value of 81.6%.

“However, it was also clear that increased mortality in RA was dependent on the disease duration/follow-up time, with the observed and expected survival curves only starting to diverge after 10 years’ disease duration.”

The SMR estimated at 10 years of follow-up was not significantly increased (SMR 1.10, 95% CI 0.85, 1.42, p = 0.44).

The study, published in the Rheumatology [link here], found excess mortality rates for RA were lower in females than males and in patients who were younger at diagnosis (41-60 years v 61-80 years).

Cause of death data showed respiratory diseases were an important underlying cause of death in RA, especially pneumonia (cause-specific SMR 5.22, 95% CI 2.26, 10.29) and interstitial lung disease (cause-specific SMR 7.64, 95% CI 2.98, 14.69), but not chronic obstructive pulmonary disease (cause-specific SMR 0.76, 95% SMR 0.25, 1.77).

There was no overall increased risk with cancer, apart from skin cancer/melanoma (cause-specific SMR 3.00, 95% CI 1.10, 6.53), and no clear evidence of increased infections, other than pneumonia (cause specific SMR 1.91, 95% CI 0.52, 4.89).

“Contrary to expectations, we found that cardiovascular disease did not contribute to increased mortality risk in ARAD RA patients,” the study said.

The study, led by rheumatologist Dr Rachel Black from the Royal Adelaide and Queen Elizabeth Hospitals, said that cardiovascular deaths also appear to be declining in RA patients in a UK study and in the general population.

“Cardiovascular disease risk in RA may arise from both inflammatory disease activity and comorbidities associated with increased cardiovascular disease risk which accrue at a greater rate in RA compared to matched controls.”

“It is likely that better management of both disease activity and comorbidities in RA patients may have contributed to this decline in cardiovascular disease mortality.”

The study said the positive finding was that Australian RA patients exposed to contemporary treatment strategies are not at increased risk of mortality in the first decade following diagnosis.

“The increase in mortality in the second decade equates to a small reduction in life expectancy of only 4 months over 20 years.”