Older adults (≥65y) comprise, on average, 18% of the total population of the European Union (EU). As of 2014, there were 22 countries in Europe with a life expectancy at birth higher than 80 years and 17 countries with a life expectancy at age 65 higher than 20 years. Life expectancy has not only been rising from birth but also at age 65. For example, life expectancy at age 65 in Portugal has increased from 20.0 years in 2004 to 21.7 in 2015 for women, and from 16.3 years to 18.0 for men during the same period, placing Portugal 0.5 years and 0.1 years above the EU28 for women and men, respectively. However, the increase in Healthy Life Years (HLY), the number of years an individual can expect to live disability-free, has not kept pace; HLY in Portugal has remained constant since 2006 and lower than the EU28 average for women and men by 4.0 and 2.8 years, respectively. Bridging the gap between life expectancy and HLY by compressing morbidity into the later years of life is of special interest; not only to increase quality of life, but also to relieve the immense strain on the healthcare systems of European countries. Diet is a major modifiable risk factor for the development and management of a range of age-related diseases that are frequently the leading causes of morbidity, disability and death in Europe. Specifically, dietary protein may slow the decline of muscle mass and function with ageing, making it a sensible candidate to prevent or modulate disability progression.
Protein malnutrition is a cause for concern in older adults in Europe since protein intake is lower in European older men (87 g/d) and women (69 g/d) than in their younger counterparts (97 g/d and 73 g/d respectively) due to multimorbidity, changes in oral health, changes in taste perception and loss of independence. Another compounding issue is that the current protein recommended dietary allowance is based largely on short-term nitrogen balance studies conducted in mainly healthy young adults, thereby failing to take into account functional outcomes, such as disability, or the higher prevalence of multimorbidity in older adults both of which can offset protein requirements due to disease-related tissue catabolism and inflammation. The InDEPENDEnt project addressed these issues by providing a robust estimate of the association between protein intake and physical function in older European and North-American adults, as well as investigating the synergistic effect of physical activity. InDEPENDEnt also reproduced these analyses on Portuguese young-old adults as well as providing up-to-date estimates on the prevalence of mobility limitations in Portugal.
