BMI: a simple, rapid and clinically meaningful index of under-nutrition in the oldest old?

Abstract

BMI is commonly used as a sole indicator for the assessment of nutritional status. While it is a good predictor of morbidity and mortality among young and middle-aged adults, its predictive ability among the oldest old remains unclear. The objective of the present study was to investigate the relationship between BMI and risk of falls, fractures and all-cause mortality among older Australians in residential aged care facilities. One thousand eight hundred and forty-six residents of fifty-two nursing homes and thirty hostels in northern Sydney, Australia, participated in the present study. Baseline weight and height were measured and BMI (kg/m2) calculated. For 2 years following the baseline measurements, incidence and date of all falls and fractures were recorded by research nurses who visited the facilities regularly and date of death was documented based on the participants' records at each facility. Cox proportional hazards regression models were calculated to determine the relationship between baseline BMI and time to fall, fracture or death, within 2 years following the baseline measures taken to be the censoring date. After adjustments were made for age, sex and level of care, low BMI (,22 kg/m2) increased the risk of fracture by 38% (hazard ratio = 1.38, 95% CI 1.11, 1.73) and all-cause mortality by 52% (hazard ratio = 1.52, 95% CI 1.30, 1.79). The magnitude of this effect was only slightly reduced when adjustments were further made to incorporate cognition, number of medications, falls and fracture in the subsequent 2-year period. In conclusion, BMI has predictive ability in the area of fracture and all-cause mortality for residents of aged care facilities. It is a simple and rapid indicator of nutritional status rendering it a useful nutrition screen and goal for nutrition intervention.