Page 81 - THE EVOLUTION OF EARLY ARTHRITIS AND CARDIOVASCULAR RISK Samina A. Turk

AN UNFAVORABLE BODY COMPOSITION
skeletal muscle mass [kg/ height2 [m2]] more than two standard deviations (SD) below
the mean of a young reference group(30). However, our patients and control group had
a mean age of 61 years, therefore we defined our own cut offs with the values of the
control group. Cut off was determined on the mean minus two times the SD (see Table
2), separated for gender and divided in three ages categories: 50-59 years, 60-69 years
and 70 year and older, as progressive loss of muscle mass occurs with advancing age(30).
Linear and logistic regression analysis were performed to measure the difference in
body composition in early arthritis patients and the general population. To correct for
multiple testing, the Benjamini-Hochberg procedure with a false discovery rate of 5%
was applied(31). 4
Next, exploratory analysis for the association of body composition and traditional risk factors in early arthritis patients were performed. Patients who used antihypertensives or statins were excluded for analyzes that involved blood pressure and cholesterol, respectively. For descriptive purposes mean (SD), median (25-75th percentile) or percentages were used, where appropriate. Comparisons between groups were made with unpaired t-tests or nonparametric tests as appropriate. Linear and logistic regression exploratory analysis were performed to measure the association between body composition, disease activity and traditional cardiovascular risk factors. Correction for multiple testing was performed with the Benjamini-Hochberg procedure with a false discovery rate of 5%.
All results are presented separately for males and females, since gender was an effect modifier. Results are corrected for confounders (demographics) where appropriate.
Table 1. Definition of obesity, based on cut offs of body fat percentages by Gallagher et al(29)
Caucasian
African
Asian
Caucasian
African
Asian
Males < 60 years
>29%
>27%
>29%
Females < 60 years
>41%
>39%
>41%
Males 60-79 years
>31%
>29%
>29%
Females 60-79 years
>43%
>41%
>41%
Table 2. Cut off points of ALMI (kg/m2) in non-arthritis controls, for defining a low muscle mass for age, stratified for gender and age categories (mean minus two times SD)
50-59 years
60-69 years
70-85 years
Number Mean males in kg/m2
198 8.8 (1.0)
137 8.5 (0.9)
53 8.1 (0.8)
Cut off males in kg/m2
<6.7
<6.8
<6.6
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