ABSTRACT
BACKGROUND: Protein intake is suggested as an important dietary factor in the prevention of frailty, however, the influence of lifelong intake remains unclear. OBJECTIVES: The present study investigated the relationship between daily protein intake and patterns of protein intake over 21 years and the risk of pre-frailty/frailty. DESIGN: Prospective cohort study. SETTING: The population-based Tromsø Study in Tromsø municipality, Norway. PARTICIPANTS: In total, 1,906 women and 1,820 men aged ≥45 years in 1994 who participated in both Tromsø4 (1994-95) and Tromsø7 (2015-16). MEASUREMENTS: Frailty status in Tromsø7 was measured according to Fried's phenotype, classifying participants as "robust" (frailty components present: 0), "pre-frail" (1-2) or "frail" (≥3). Daily intake of protein was estimated from self-reported habitual dietary intake using food frequency questionnaires and assessed as grams per kilogram bodyweight (g/kg BW) and per megajoule energy intake (g/MJ). The protein-frailty association was assessed via longitudinal and cross-sectional multivariable logistic regression analyses. RESULTS: The prevalence of pre-frailty and frailty in this study was 27% and 1.0%, respectively. Longitudinal analysis showed that the odds of pre-frailty/frailty decreased by 57% (odds ratio (OR) = 0.43, 95% confidence interval (CI) = 0.31;0.58, p<0.001) with the increase in intake of one additional gram of dietary protein per kg BW. The results obtained from cross-sectional analysis were similar. Tracking analysis showed that, compared to a stable high intake of protein in g/kg BW over time, other patterns of protein intake increased the risk of pre-frailty/frailty. No associations were found between intake of protein in g/MJ and pre-frailty/frailty. CONCLUSIONS: Intake of protein in g/kg BW both in mid-life and later in life was inversely associated with pre-frailty/frailty in older adults. This emphasizes the importance of an adequate protein intake to facilitate healthy ageing in Norwegian older adults.