Obese RA Patients Outlive Thin RA Patients - CME Teaching Brief - MedPage Today

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Obese RA Patients Outlive Thin RA Patients

By Neil Osterweil, Senior Associate Editor, MedPage Today

Reviewed by Rubeen K. Israni, M.D., Fellow, Renal-Electrolyte and

Hypertension Division, University of Pennsylvania School of Medicine

July 25, 2005

MedPage Today Action Points

* Inform patients that while this study found lower mortality rates

among people with RA who are overweight or obese, this finding did not

hold true when comorbidities and RA severity were taken into account.

* Reassure patients with RA that there are many factors affecting

survival, and that the findings in this study need to be confirmed by a

clinical trial.

Review

SAN ANTONIO, July 25-Obese and overweight patients with rheumatoid

arthritis had paradoxically lower death rates than normal weight or

thin RA patients, researchers here reported today.

That's the conclusion of a team at the University of Texas Health

Sciences Center here, who detected a paradoxical effect of body mass

index (BMI) on mortality among patients with RA. Just why being too fat

might bestow a survival advantage was not clear.

" This represents a paradoxical effect of BMI on mortality, being

counter to what occurs in apparently healthy individuals, " wrote

Augustin Escalante M.D. and colleagues in the July 25 issue of the

Archives of Internal Medicine. " In the general population, mortality

reaches its highest rate among people in the top BMI categories.

Obesity is a risk for [cardiovascular] disease and may raise the risk

of death from other causes. The lower mortality rate we observed among

the heaviest patients in this RA cohort was thus unexpected. "

There could be an unknown protective effect of fat, they suggested, or

it could be that thinner people with RA are at greater risk for death

because of a higher degree of co-morbidity.

The investigators had originally suspected that higher BMI would have a

negative effect on survival, modified by markers of inflammation. To

test this idea, they looked at the effects of BMI on survival in a

cohort of 779 consecutive patients with RA who were enrolled at six San

-area rheumatology clinics.

The investigators calculated BMI for each patient at each visit, and

categorized them as underweight (BMI less than 20), normal weight (BMI

20 to <25), overweight (BMI 25 to < 30) or obese (BMI > 30). The data

were adjusted for comorbidities, RA severity, erythrocyte sedimentation

rate, and other potential confounding factors.

During the follow-up period, the patients racked up a total of 3,460

person-years of observation. There were 123 deaths, translating into a

mortality rate of 3.6 per 100 person-years (95% CI, 3.0-4.2). The age

and sex-adjusted morality rates (95% CI) were 6.8 (4.2-11.1) in the

underweight patients, 3.3 (2.3-4.9) in the normal weight patients, 2.1

(1.4-3.0) among the overweight group, and 1.4 (0.1-1.2) among the obese

patients.

" It should be noted that in contrast to findings in the general

population where a J- or U-shaped association between BMI and mortality

is seen, the present cohort displayed a near-linear decrease in

mortality from the lowest to the highest BMI category, " Dr. Escalante

and colleagues wrote. " This was the case in both the gross and

age-adjusted mortality rates. "

Higher BMI was associated with longer survival independent of factors

such as the age of RA onset or disease duration, gender, ethnicity,

socioeconomic status, smoking or methotrexate use. The survival

advantage disappeared, however, when they adjusted the data for

comorbidity and RA severity.

" We observed an interaction between BMI and erythrocyte sedimentation

(ESR) rate, where the BMI's protective influence occurred only if the

ESR was low. The BMI-ESR interaction was independent of all covariates,

including comorbidity and RA severity, " the authors noted.

They cautioned that their data are preliminary and should not be used

as a basis for recommending weight changes in patients with RA.

" The BMI is subject to multiple potential influences, and we could

adjust for only a limited number of these, " the investigators

commented. " Any recommendation for weight modification should be based

on evidence from controlled trials. There is currently limited

information suggesting that a weight loss program might improve

physical fitness in obese patients with RA. "

Primary source: Archives of Internal Medicine

Source reference:

Arch Intern Med. 2005;165:1624-1629

http://www.medpagetoday.com/Rheumatology/Arthritis/tb1/1418