Nutritional status, body composition and diet in patients with rheumatoid arthritis
Sammanfattning: Rheumatoid arthritis (RA) is a chronic inflammatory disease with higher mortality rate than in the general population, which is largely attributed to cardiovascular disease (CVD). Another consequence of the inflammatory process is change in body composition with decreased muscle mass and increased fat mass. This condition has been named rheumatoid cachexia and is difficult to detect in clinical practice, as it is associated with little or no weight loss and with a maintained body mass index. The aims of this thesis were to evaluate different diagnostic instruments for assessment of nutritional status and body composition in patients with RA and to study if the diet was associated with body composition derangement and dyslipidemia, especially antibodies against phosphorylcholine (anti- PC). In- and out-ward RA patients at the Karolinska University Hospital and Södersjukhuset in Stockholm were included in the studies. They were assessed by anthropometric measures, dual-energy x-ray absorptiometry (DXA), bioelectrical impedance analyses (BIA) and nutritional questionnaires. Further blood samples and adipose tissue were analysed. Sixty-six patients were randomized to either a vegan diet free of gluten or a well-balanced non-vegan diet for 1 year and assessed as to disease activity and dyslipidemia. Twelve per cent of the in-ward women, only one of the out-wards and none of the men had BMI<18.5, the cutoff value for malnutrition. Fifty-two percent of the in-ward women and 30% of the men were malnourished, according to fat free mass index (FFMI). Corresponding figures for the out-ward women and men were 26% and 21%, respectively. Reduced FFM was independently related to age, disease duration, erythrocyte sedimentation rate (ESR) and function trendwise. However, these patients also displayed central obesity in 57% of the women and in 89% of the men. About every fifth patient displayed concomitant low fat free mass (FFM) and elevated fat mass (FM), i.e. rheumatoid cachexia. These patients had significantly higher total cholesterol, LDL, and trendwise oxLDL as well as lower anti-PC, higher frequency of hypertension (69%) and metabolic syndrome (25%) than those without rheumatoid cachexia. The anthropometrical measurements showed low sensitivity and high specificity for detecting malnutrition. Of the nutritional questionnaires Mini Nutritional Assessment (MNA) had the highest sensitivity but the specificity was low. There was a good relative agreement between DXA and BIA assessing body composition (FM, r2=0.94, FFM, r2=0.92; both p<0.001), but the limits of agreement were wide for each variable, i.e. for FM -3.3 to 7.8 kg; and for FFM -7.9 to 3.7 kg. The patients reported a high dietary intake of saturated fat. However, patients with or without cachexia did not differ with respect to dietary fat intake or intake of mediterranean like diet. Patients on mediterranean like diet though had high levels of anti-PC. Gluten-free vegan diet induced lower low-density lipoprotein (LDL) levels and higher anti-PC IgM than a normal western diet (p < 0.005). In conclusion, a large proportion of RA patients had reduced FFMI and central obesity. Rheumatoid cachexia was common and was not associated with dietary fat intake but with high LDL and low anti-PC levels. Gluten-free vegan diet in RA induced changes in serum lipids that are potentially atheroprotective and anti-inflammatory. Of the tested clinical evaluation tools, MNA might be used as a screening instrument. There was a good relative agreement between DXA and BIA, but the limits of agreement were wide, which may restrict the utility of BIA in clinical practice.
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