Body mass index, waist circumference and pre-frailty/frailty: the Tromsø study 1994−2016

Objective This study investigated the association between obesity, assessed using body mass index (BMI) and waist circumference (WC), and pre-frailty/frailty among older adults over 21 years of follow-up.Design Prospective cohort study.Setting Population-based study among community-dwelling adults in Tromsø municipality, Norway.Participants 2340 women and 2169 men aged ≥45 years attending the Tromsø study in 1994–1995 (Tromsø4) and 2015–2016 (Tromsø7), with additional BMI and WC measurements in 2001 (Tromsø5) and 2007–2008 (Tromsø6).Primary outcome measure Physical frailty was defined as the presence of three or more and pre-frailty as the presence of one to two of the five frailty components suggested by Fried et al: low grip strength, slow walking speed, exhaustion, unintentional weight loss and low physical activity.Results Participants with baseline obesity (adjusted OR 2.41, 95% CI 1.93 to 3.02), assessed by BMI, were more likely to be pre-frail/frail than those with normal BMI. Participants with high (OR 2.14, 95% CI 1.59 to 2.87) or moderately high (OR 1.57, 95% CI 1.21 to 2.03) baseline WC were more likely to be pre-frail/frail than those with normal WC. Those at baseline with normal BMI but moderately high/high WC or overweight with normal WC had no significantly increased odds for pre-frailty/frailty. However, those with both obesity and moderately high/high WC had increased odds of pre-frailty/frailty. Higher odds of pre-frailty/frailty were observed among those in ‘overweight to obesity’ or ‘increasing obesity’ trajectories than those with stable normal BMI. Compared with participants in a stable normal WC trajectory, those with high WC throughout follow-up were more likely to be pre-frail/frail.Conclusion Both general and abdominal obesity, especially over time during adulthood, is associated with an increased risk of pre-frailty/frailty in later years. Thus maintaining normal BMI and WC throughout adult life is important