Body mass index, Mini Nutritional Assessment, and their association with five-year mortality in very old people

to investigate the prevalence of malnutrition and the association between Body Mass Index (BMI), Mini Nutritional Assessment (MNA) and five-year mortality in a representative population of very old (>85 years) people.

A prospective cohort study.

A population-based study of very old people in northern Sweden and western Finland, living in institutional care or in the community.

Out of 1195 potential participants, 832 were included (mean age 90.2±4.6 years).

Nutritional status was assessed using BMI and MNA and the association of those two variables with five-year mortality was analyzed.

The mean BMI value for the whole population was 25.1±4.5 kg/m2, with no difference between genders (P=0.938). The mean MNA score was 22.5±4.6 for the whole sample, and it was lower for women than for men (P<0.001). Thirteen percent were malnourished (MNA<17) and 40.3% at risk of malnutrition (MNA 17-23.5) according to MNA. Also, 34.8% of those with a MNA score <17 still had a BMI value ≥22.2 kg/m2. A BMI value <22.2 kg/m2 and a MNA score<17 were associated with lower survival. The association with mortality seemed to be J-shaped for BMI, and linear for MNA.

Malnutrition according to MNA was common, but a substantial portion of those with a low MNA score still had a high BMI value, and vice versa. The association with mortality appeared to be J-shaped for BMI, and linear for MNA. The MNA seems to be a good measurement of malnutrition in very old people, and BMI might be misleading and could underestimate the prevalence of malnutrition, especially in women.