Xuxi Zhang

1.1 BACKGROUND  According to the data from World Population Prospects 2019, the proportion of the  population aged over 65 years will increase from 9% in 2019 to 16% in 2050, and the number  of people aged over 80 years is projected to triple, from 143 million in 2019 to 426 million in  2050. 1  Globally, the older population grows bigger due to the increasing longevity and  decreasing fertility. 1, 2  People may experience multiple challenges from the physical,  psychological and social perspectives when they grow older. People aged over 65 years are  presumed to live almost half of their remaining lives with a limiting long‐term physical or  mental condition. 3  Therefore, alongside with the extension of life quantity among the  increasingly older population, it is important to find out novel ways to improve people’s  health and quality of life during the extended years. 2, 4 Healthy Ageing  The concept of healthy ageing was first put forward by Robetr Havighurst in 1961, by which  he meant that older adults prefer to stay actively involved in the activities that they were  engaged in in their earlier life. 5  With the increase of older people worldwide, healthy ageing  attracts more and more attention in recent decades. In 2002, the World Health Organization  (WHO) defined healthy ageing as “the process of developing and maintaining the functional  ability that enables wellbeing in older age”. 6  WHO general director Margaret Chan, at that  time, emphasized that “healthy ageing is more than just the absence of disease; the  maintenance of functional ability has the highest importance”. 7  The requirement of healthy  ageing is not the absence of disease or infirmity because there will inevitably occur relatively  more chronic and acute conditions for older adults with the increasing longevity. 6  The  challenge of healthy ageing is to manage and live well with the conditions, and make their  influence on people’s wellbeing less. 6 Healthy ageing is a life‐long process, and life choices or interventions at different points during  the life course may determine the functional trajectory of each individual. 7, 8  The most  favorable outcome is to maintain intrinsic capacity, and live in functional independence within  your own surroundings until the end of life. 7, 8 In order to realize healthy ageing, the society should take actions against risk factors for  (future) disability and dependency throughout the life cycle. The risk factors related to healthy  ageing could be divided into four categories: (1) “non‐modifiable” risk factors, such as  genetics, gender and ethnic background, (2) “distal” risk factors, such as economic  background, socio‐cultural determinants, education and air pollution, (3) “intermediate” risk  factors, such as health behaviors, living and working conditions and access to healthcare, and  (4) “proximal” risk factors, such as frailty, chronic conditions (e.g. hypertension and diabetes)  and cognitive impairments. 8, 9  Since the “proximal” risk factors are most closely related to  health conditions and disability, actions targeted at these factors are often considered to be  the priority in promotion of healthy ageing. 8  Therefore, in this thesis, we studied health  1 13 General introduction