Both obesity and underweight are associated with impaired physical functioning, but related information on the oldest old population is scarce. Our purpose was to examine whether body mass index, waist circumference (WC), and their combination are associated with physical performance and activities of daily living (ADL) disability in 90-year-old women and men.

Data are from the Vitality 90+ Study, which is a population-based study of persons with age ≥90 years living in the area of Tampere, Finland. Altogether 416 women and 153 men, aged 90-91 years, provided data on body mass index, WC, chair stand, and Barthel Index. Comorbidity, physical exercise, smoking history, living residence, and sample year were used as covariates in multinomial logistic and logistic regression models.

Women in the highest WC tertile had lower physical performance and were more likely unable to perform the chair stand than women in the lowest WC tertile. Women in the highest WC tertile were also more likely to have ADL disability, compared to the lowest WC tertile. In women, overweight and obesity were associated with ADL disability, but not when WC was included in the model. Men with body mass index ≥25kg/m² and WC < sex-specific median were less likely to have ADL disability. Similarly classified women were less likely to have low performance or unable to perform chair stand (marginally significant).

High WC in the oldest old women, but not in men, is associated with both poor physical performance and ADL disability.