The efforts for associating a positive concept to the ageing process is not a recent endeavor. In the 44th century BC, Cicero described ageing as a time of opportunities for positive change and productive functioning, while in the 1940s the use of the successful ageing concept was linked to the first attempts to develop indicators to determine the degree of satisfaction with life by the American Social Science Research Council [20]. Later, in 1961, Havighurst adopted it, describing the successful ageing as an adaptive theory and a testable experience [21]. This term was popularized by Rowe and Kahn, which concentrated on differentiate "usual or normal" ageing from "successful" ageing. These authors developed the successful ageing concept to encompass older adults who have a low probability of disease and disability, high physical and cognitive capacity and an active commitment to life [22]. However, this conceptualization has been widely criticized for its restrictive nature [23]. In addition, this conceptualization of successful ageing neglects the effect of the sociocultural context and the older population's opinion of their own ageing experience and overestimates the role of individual behavior [3–4, 20, 22].
Other attempts to describe the ageing process from a positive perspective have been done in the European Region. On 2002, the concept of active ageing was introduced with the aim of influencing the determinants of ageing related to socio-health systems and the environment [24]. “Active” was defined as a continuous participation in social, economic, cultural, spiritual and civic aspects and not only the ability to stay physically active or participate in the workforce [24]. But this model has not been validated either. Paúl et al., demonstrated that most of the determinants of this model were not independent [25]; while Bélanger et al. concluded that the active ageing concept could be considered as a human rights policy orientation rather than an empirical measurement tool [26]. Likewise, other authors have pointed out the risk of discrimination that exists when idealizing the concept of active ageing, as a status that all the older population should reach [24].
The interest in demonstrating that the ageing process isn’t homogeneous is not a novel concern. By using different conceptualizations, many researchers have tried to describe the differences among those who age in better conditions and those who don’t. The huge differences found by McLaughling et al. and Rodriguez-Laso et. al in the prevalence of healthy ageing in the United States and Spanish population, respectively, highlighted the need to use a more comprehensive criteria to identify the older population who is ageing in a better condition [3–4]. The present study contributes with a novel multidimensional model to assess the healthy ageing at population level, using a less rigorous definition, based on the WHO concept of healthy ageing [5] and environment components.
The domains considered for the multidimensional model offer a more comprehensive view of healthy aging; includes the following components: a) intrinsic capacity, which integrates elements of the physical and mental health, such as geriatric syndromes, risk factors, physiological and metabolic helth, cognitive function, physical capacity, and psychological well-being, b) social and political environment, and c) the interaction of the older adult with their environment. These components, in turn, determine the functional capacity of the older adult (Fig. 2). This comprehensive model breaks the paradigm that healthy is equal to the absence of physical illness.
According this model, in Ecuador, slightly more than half of the older population is ageing healthily (53.15%). This result is above the data reported in the United States and Spain [3–4]. This can be explained partly due to the sociodemographic differences of the older adults included in the different studies, but particularly by the healthy ageing model applied in the present investigation. In our model, the intrinsic capacity of an older person was not limited to the absence of a disease or risk factors. As previous studies have shown that, despite physical limitations and structural obstacles, older people can be considered successful or active, given the compensation process they go through as they age [25, 27].
An interesting finding after the bi-stage cluster analysis is the similarity of the two groups, healthy and less healthy, in the domain of risk factors. This behavior could show that, there are other elements that influence in the healthy ageing. Previous research has demonstrated that certain risk factors such as: obesity, sedentary lifestyle, smoking, alcohol consumption, have a great impact on the ageing process; but others elements, including demographic, epidemiological geographical, or economic situation, could affect how each person ages [28].
When analyzing the characteristics of the healthy ageing and less healthy ageing groups, the differences by sex stand out. This could be explained by to the association described between high levels of multimorbidity and female sex, where older women show a worse health status when compared to men of the same age [29]. Yet, other authors have pointed out that this association is more linked to age than sex, since it has been seen that after the age of 80 the differences in health status by sex are reduced [30–31]. In our study, the association between less healthy and female sex was maintained after adjusting for age and other variables, which points to gender inequalities in the way of aging.
Other variables that were associated with healthy aging were age, educational and economic level. A positive association between age and the presence multimorbidity and disability has been widely recognized [30, 32]. Several studies have shown that the level of education of an older person is associated with the level of understanding of health issues, access to health services and adherence to medical treatments. [33–37].
According to our data, older adults in the worst economic situation are less likely to be in the healthy ageing group, making them a highly vulnerable group. There is vast evidence of the association between a low socioeconomic level and poorer physical and mental health in older adults, as a consequence of exposure to a greater number of risk factors, anxiety, and less access to health services in younger ages [38–40]
In the present study, no significant difference was found between living in an urban or rural area. The combination of an unfavorable external environment for the older population, as well as personal poverty increase their risk of having a poor physical, psychological and mental health status, social isolation, and higher risk of death [5, 41–42]. For this reason, the limitations of the environment, and not simply the place of residence, could be a more important factor to consider when defining whether an older person is ageing in a healthy way or not.
In addition, the self-perception that older adults have about their health, life and mood is important. In our study, the majority of older adults who had a positive perception of their health were categorized in the healthy ageing group. This may be because the healthy ageing group includes people with the best intrinsic ability and a suitable environment that responds to their needs. This is what is known as the “disability paradox” [43]. The well-being and satisfaction for a person, even in physiological conditions or severe disability, is explained by their ability to adapt to their condition, and the balance achieved between their intrinsic capacity and the environment [43–44].
We have some limitations in this study. The use of secondary source data restricted the model to existing variables to determine the domains. The absence of a unified and operational definition of healthy ageing makes a direct comparison between studies impossible. It would be important replicated this study in different populations, to obtain a better understanding of the proposed healthy ageing model. This study have some strengthens. It contributes to the methodological discussion on healthy aging and proposes a multidimensional model for its measurement and comparison between countries. To the knowledge of the authors, the use of a definition of healthy ageing based on ten domains, which consider not only the intrinsic capacity of the person, but also their environment and their interactions with it, has not been described in previous studies. Some studies have reported the ability of the older adult population to adapt to their new conditions, so qualify a person based on the presence or absence of a disease, without taking into account whether or not it affects their functionality in life daily, it is inappropriate. The model applied in this study contributes not only to understanding the heterogeneity of ageing, but also to identifying the group of older adults who need to be prioritized in public policies. This evidence suggests the importance of healthy aging policies focused on improving socioeconomic conditions and reducing gender inequalities. On the other hand, it would be important that this study can be replicated in countries with different characteristics, to corroborate the proposed multidimensional healthy ageing model.