Association between dietary protein intake and changes in health-related quality of life in older adults: findings from the AusDiab 12-year prospective study

Background Adequate dietary protein intake is recommended for older adults to optimise muscle health and function, and support recovery from illness, however, its effect on health-related quality of life (HRQoL) is unclear. The aim of this study was to examine the association between total protein intake and different sources of dietary protein and HRQoL in Australians aged 60 years and older over a 12-year period. Methods This study used data from the Australian Diabetes, Obesity and Lifestyle study (AusDiab), a 12-year population-based prospective study. The sample included 752 (386 females) adults aged 60 years and older. Protein intake was estimated at baseline (1999/2000) from a 74-item Food Frequency Questionnaire, and HRQoL using the 36-item Short-form Health Survey assessed at baseline (1999/2000) and after 12 years (2011/12). The association between protein intake and change in HRQoL was evaluated using multivariate regression analysis adjusted for relevant confounders. The difference in change in HRQoL between participants with total protein intakes of < 1.0 g/kg/day, intakes of between 1.0-1.2 g/kg/day and intakes of > 1.2 g/kg/day were assessed using one-way ANCOVA. Results Total protein intake at baseline was not associated with 12-year changes in physical component summary (PCS) or mental component summary (MCS) scores of HRQoL. Higher animal, red meat and processed animal protein intakes were associated with deteriorations in PCS scores after adjusting for relevant confounders (beta = - 0.04; 95% CI: - 0.07, -0.01 ; p = 0.009; beta = - 0.05; 95% CI: - 0.08, - 0.01; p = 0.018; beta = - 0.17; 95% CI: - 0.31, - 0.02; p = 0.027 respectively). Higher red meat protein intake was associated with deteriorations in MCS scores after adjusting for relevant confounders (beta = - 0.04; 95% CI: - 0.08, - 0.01; p = 0.011). There was no difference in 12-year changes in PCS or MCS between participants consuming total protein of < 1.0 g/kg/day, 1.0-1.2 g/kg/day and intakes of > 1.2 g/kg/day. Conclusion There was no relationship between total dietary protein intake and HRQoL, but higher protein intakes from animal, red meat and processed animal sources were associated with a deterioration in HRQoL scores over 12 years. Due to the number of associations examined and high drop out of older less healthy participants, further research is required to confirm the associations detected in healthy and less healthy participants, with a view to making protein intake recommendations for older adults.