BACKGROUND: Low fat-free mass (FFM) is a risk factor for morbidity and mortality in elderly and patient populations. Therefore, measurement of FFM is important in nutritional assessment. Bioelectrical impedance analysis (BIA) is a convenient method to assess FFM and FFM index (FFMI; FFM/height(2)). Although reference values have been established for individuals with normal body weight, no specific cutoff values are available for overweight and obese populations. Also, limited studies accounted for the age-related decline in FFM.
OBJECTIVE: To determine BMI- and age-specific reference values for abnormal low FFM(I) in white-ethnic men and women free of self-reported disease from the general population.
DESIGN: The UK Biobank is a prospective epidemiological study of the general population from the United Kingdom. Individuals in the age category 45 to 69 years were analyzed. In addition to body weight, FFM and FFMI were measured using a Tanita BC-418MA. Also, self-reported chronic conditions and ethnic background were registered, and lung function was assessed using spirometry.
RESULTS: After exclusion of all individuals with missing data, nonwhite ethnicity, self-reported disease, body mass index (BMI) less than 14 or 36 kg/m(2) or higher, and/or an obstructive lung function, reference values for FFM and FFMI were derived from 186,975 individuals (45.9% men; age: 56.9 6.8 years; BMI: 26.5 3.6 kg/m(2); FFMI 18.3 2.4 kg/m(2)). FFM and FFMI were significantly associated with BMI and decreased with age. Percentiles 5, 10, 25, 50, 75, 90, and 95 were calculated for FFM, FFMI, and fat mass (index), after stratification for gender, age, and BMI.
CONCLUSIONS: Using the UK Biobank dataset, new reference values for body composition assessed with BIA were determined in white-ethnic men and women aged 45 to 69 years. Because these reference values are BMI specific, they are of broad interest for overweight and obese populations.
Franssen FM, Rutten EP, et al New reference values for body composition by bioelectrical impedance analysis in the general population: results from the UK Biobank. Spruit MA4.J Am Med Dir Assoc. 2014 Jun;15(6):448.e1-6. doi:10.1016/j.jamda.2014.03.012. Epub 2014 Apr 20.
Development of BMI specific cut offs for fat free mass index
An abnormal low fat-free mass index (FFMI) occurs frequently in patients with chronic organ failure, such as chronic obstructive pulmonary disease (COPD), and is a strong determinant of morbidity and mortality. Moreover, FFMI provides information on prognosis in addition to body mass index. Therefore, assessment of FFMI should be considered in the routine assessment of COPD.
An abnormal low fat-free mass index (FFMI) occurs frequently in patients with chronic organ failure, such as chronic obstructive pulmonary disease (COPD) (Schols et al. ARRD 1989). Moreover, FFMI provides information on prognosis in addition to body mass index (Vestbo et al. AJRCCM 2005). Therefore, assessment of FFMI should be considered in the routine assessment of COPD. The current gender-specific cut off values for an abnormal low FFMI are based on the lowest 10th percentile of the general population (mean BMI: 26 kg/m2). Nevertheless, in our daily clinical practice, we experience that COPD patients with an overweight BMI (25 to 30 kg/m2) or obese BMI (>30 kg/m2) never have an abnormal low FFMI. Therefore, we suggest to develop BMI-specific cut offs for abnormal low FFMI in men and women. Obviously, the clinical relevance of these newly developed cut offs need to be determined prospectively in clinical cohorts, including patients with chronic organ failure.
|Lead investigator:||Martijn Spruit|
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