engleski

Optimal weight in the elderly: should new BMI criteria be used?

BACKGROUND: The commonly used upper limit of ideal weight for all adults defined by the body mass index (BMI) of 25 kg/m2 has been questioned in the elderly. The prognostic importance of overweight/obesity in very old persons is largely controversial. We examined the suggested higher BMI cut-off level in defining optimal weight of persons aged 85+ years based on the relationship of BMI to waist circumference (WC) and arm fat index (AFI) as the indicators of body fatness. METHODS: In 328 individuals, both sexes, age 85-101 yrs, living in retirement homes (Zagreb, Croatia), height, weight, circumferences (waist, mid-upper arm), and triceps skinfold were measured and used to calculate BMI and AFI at the crossectional mid- upper arm area. Sensitivities and specificities of the proposed BMI levels in relation to the cut-off points for WC and AFI were calculated. Also, relationship of BMI with functional ability (mobility, independence, cognitive ability) was investigated. RESULTS: There were 2% of underweight (BMI<18.5), 41% of overweight (BMI 25.0-29.99), and 27% of obese (BMI>=30) persons. At the BMI cut-off level of 25 kg/m2, sensitivity was 84.9% for detecting those with low WC (<=102 cm in men ; <=88 in women). At the levels 27 kg/m2 and 30 kg/m2, sensitivity for detecting those with low WC was 76.4% and 56.4%, respectively. Specificities at the three examined BMI levels grew from 78.5% to 98.9%. Similar sensitivities and specificities were obtained when the combination of WC and AFI (low AFI defined as <3rd sex-specific tercile of the sample) were applied. BMI showed significant positive relationship with mobility and independence. CONCLUSION: Standards for optimal weight (BMI 18.5-24.99) may be overly restrictive as they apply to the very old persons.

body mass index ; cut-offs ; waist circumference ; arm fat index ; oldest olds ; Croatia

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