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Title: Protein intake and functional integrity in aging: the Framingham Heart Study offspring

item HURBY, ADELA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item SAHNI, SHIVANI - Harvard University
item BOLSTER, DOUGLAS - Danone Institute International
item JACQUES, PAUL - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Journal of Gerontology Medical Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2018
Publication Date: 9/24/2018
Citation: Hurby, A., Sahni, S., Bolster, D., Jacques, P.F. 2018. Protein intake and functional integrity in aging: the Framingham Heart Study offspring. Journal of Gerontology Medical Science.

Interpretive Summary: Aging is associated with many physiological and metabolic changes that are partially driven by nutrition. Dietary protein has been thought to positively influence healthy aging; however, to date, most studies have focused on the role of protein in bone and muscle health. Promoting maintenance of healthy bone and muscle is critical to helping older adults maintain their physical function and independence. Yet, research around the role of protein in preventing frailty, disability, and physical dysfunction is limited; in particular, few long-term studies have been conducted. In addition, studies have been limited to narrow populations (ie. with respect to gender), focused on limited outcomes, or utilized relatively short periods of follow-up. Thus, our aim was to use data from a long prospective cohort study (>20 y) to examine associations between protein intake and maintenance of physical function and prevention of physical disability with the hypothesis that higher protein intake would be associated with maintenance of function. We examined nearly 3,000 participants from the Framingham Heart Study Offspring cohort over a >20 year timeframe. Protein intake was determined using a food frequency questionnaire. We created a functional integrity score (FIS) which represents 17 measures of function including, but not limited to, activities such as dressing, bathing, and eating, heavy work, walking up stairs, pulling and pushing objects, reaching, writing, and sitting. Better FIS was correlated with lower odds of falls, fractures, and frailty. Participants in the highest category of protein intake had a 30% lower risk of functional integrity loss compared to participants in the lowest category of protein intake. When examined with respect to sex (sex-stratified), the reduced risk of functional integrity loss was evidence among women. Our results suggest that optimizing protein intake may play a role in both helping to preserve muscle mass and strength, and in maintaining functional integrity, specifically, protecting against frailty and falls and helping to maintain independence among aging adults.

Technical Abstract: Background: Higher protein intake is linked to maintenance of muscle mass and strength, but few studies have related protein to physical function and disability in aging. Methods: In initially high-functioning participants of the Framingham Heart Study Offspring, we examined associations between protein intake (g/d), estimated from food frequency questionnaires, and maintenance of functional integrity, as a functional integrity score (FIS) based on responses to 17 questions from Katz Activities of Daily Living, Nagi, and Rosow-Breslau questionnaires, repeated up to 5 times (1991/95-2011/14) over 23 years of follow-up. Adjusted cox proportional hazard models were used to estimate the risk of incident loss of functional integrity (FIS <15th percentile) across quartile categories of protein intake. Results: In 2,917 participants (age 54.5 [9.8] y), baseline protein intake was 77.2 [15.6] g/d. The FIS (at baseline, mean 98.9, range 82.4-100.0) correlated with objective performance (gait speed, grip strength), and higher scores were associated with lower odds of falls, fractures, and frailty. Across follow-up, there were 731 incident cases of loss of functional integrity. In fully adjusted models, participants in the highest category of protein intake (median 92.2 g/d) had 30% lower risk of loss of functional integrity (HR [95%CI] 0.70 [0.52-0.95], P trend=0.03), versus those with the lowest intake (median 64.4 g/d). In sex-stratified analyses, the association remained in women alone. Conclusions: Higher protein intake was beneficially associated with maintenance of physical function in middle-aged, high-functioning US adults over the span of two decades. This association was particularly evident in women.