Obesity Is Boon Only for Bone in Rheumatoid Arthritis

December 19, 2017

Findings from this study may explain the “obesity paradox” for mortality in patients with RA.

Key points
• Women with and without a recent diagnosis of rheumatoid arthritis (RA) who experienced severe weight loss (> 30 lb) were at increased risk for dying compared with women whose weight was stable.

• Women with RA continue to have a higher absolute risk of death compared with healthy subjects; however, their mortality risks were similar with regards to weight trends.

• While obesity may decrease the risk of bone erosions in RA, it appears to confer no benefit with regards to mortality.

Background
Patients with RA are at higher risk for dying than the general population. Recent studies have also shown a possible reduction in mortality in patients with RA who are obese.

Sparks and colleagues at Harvard Medical School in Boston state that “this ‘obesity paradox’ for mortality in RA may be explained by pathologic unintentional weight loss in the few years preceding death rather than a biologic protective effect of obesity.”1

The researchers sought to determine the effect of weight change on mortality in RA. They presented their findings recently in Arthritis & Rheumatology.

The study
The authors conducted a retrospective cohort study utilizing the Nurses’ Health Study, a database started in 1976, which followed 121,701 female registered nurses in the United States. Subjects were included if they had no prior connective tissue diagnosis. Subjects with RA were matched with non-RA subjects and compared with regards to weight gain or loss and mortality.

The results
• 902 subjects with RA and 7884 matched healthy comparators were included in the final analysis.

• Most subjects maintained stable weight (64.3% in the RA cohort and 69.1% in the comparison cohort).

• More women in the RA cohort lost weight (15.8% vs 10.6% of healthy comparators), with severe weight loss in 3.0% of RA subjects vs 1.6% of comparators.

• Similar rates of weight gain (19.9% vs 20.5%) and severe weight gain (2.4% vs 2.3%) were observed between cohorts, respectively.

• In total, 371 deaths (41.1%) occurred during 16,006 person-years of follow-up in RA subjects vs 2303 (29.2%) during 150,075 person-years in the comparator group.

• No statistically significant relationship was found between moderate weight loss or any amount of weight gain and mortality.

• Severe weight loss was associated with increased mortality in the peri-RA period (hazard ratio [HR], 3.51; 95% confidence interval [CI], 2.12-5.80).

• Mild weight loss conferred a lower HR than severe (1.72; 95% CI, 1.22-2.42).

• Severe weight loss remained a significant predictor of mortality following adjustments in both the RA and comparator groups.

• Survival was consistently and significantly worse in patients with severe weight loss (P < .0001 for both the RA and comparator cohorts).

• In the non-RA cohort, both severe weight loss and weight gain were significantly related to mortality (HR, 2.42; 95% CI, 1.81-3.22; for severe gain: HR, 1.36; 95% CI, 1.01-1.81).

Implications for physicians
• Physicians should be vigilant for large weight changes both in their patients with RA and in those who do not have RA.

• Although higher weight appears to be associated with less joint damage in RA, it does not confer a mortality benefit.

• Large increases and decreases in weight raise the risk of death regardless of RA.

Disclosures:

The Rheumatology Research Foundation and the NIH supported this study.

References:

1. Sparks JA, Chang SC, Nguyen US, et al. Weight change during the early rheumatoid arthritis period and risk of subsequent mortality in women with rheumatoid arthritis and matched comparators. Arthritis Rheumatol. 2017 Nov 30. doi: 10.1002/art.40346. [Epub ahead of print]