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A LITERATURE REVIEW OF HEALTHY AGING TRAJECTORIES THROUGH QUANTITATIVE AND QUALITATIVE STUDIES: A PSYCHO-EPIDEMIOLOGICAL APPROACH ON COMMUNITY-DWELLING OLDER ADULTS

A. Zamudio-Rodríguez1, J.-F. Dartigues1, H. Amieva1, K. Pérès1

1. University of Bordeaux, Inserm, Bordeaux Population Health Research Center, UMR 1219, Bordeaux, France.
Corresponding author: Alfonso Zamudio Rodríguez. Centre de recherche Inserm, UMR 1219. Rue Léo Saignat, 33076 Bordeaux cedex, France. Phone: +33 (5) 57.57.11.73. Fax: +33 (5) 57.57.14.86, E-mail: alfonso.zamudio-rodriguez@u-bordeaux.fr

J Frailty Aging 2020;in press
Published online November 24, 2020, http://dx.doi.org/10.14283/jfa.2020.62


Abstract

The population of older adults over 60 years is growing faster than any other age group and will more than double between 2020 and 2050. This increase has led to clinical, public health, and policy interest in how to age “successfully”. Before the Rowe and Kahn’s model proposed thirty years ago, aging was seen as a process of losses associated with diseases and disability. However, since the emergence of this model, there has been a shift towards a more positive view, serving for promoting diverse medical or psychosocial models, and personal perspectives. Several technical terms of “success” (e.g. “successful aging”, “healthy aging”, “active aging”, “aging well”…) coexist and compete for the meaning of the concept in the absence of a consensual definition. Our literature review article aims to study discrepancies and similarities between the main technical terms through quantitative or qualitative studies. A literature review using PubMed, SCOPUS, PsycINFO, Psycarticles, Psychology, and Behavioral Sciences Collection, Cochrane database, and clinicaltrials.gov databases was conducted. A total of 1057 articles were found and finally, 43 papers were selected for full extraction. We identified several components in these definitions, which reveal considerable inconsistency. The results particularly suggest that lay personals perspectives could bridge the gap between biomedical and psychosocial models in successful aging. In conclusion, an optimal definition would be a multidimensional one that could combine functional capacities, psychosocial abilities, environmental factors and subjective assessments of one’s own criteria to discriminate older adults at potential risk of “unsuccessful” aging to healthy aging trajectories.

Key words: Healthy aging, public health, review, successful aging, theorical models.


 

Introduction

More people than ever before are reaching older ages. The proportion of people over 60 years is growing faster than any other age group due to both increasing longevity and declining fertility rates. Furthermore, in many industrialized countries, the first generations after the Second World War are currently reaching old age, the so-called baby boomers. The current aging population will more than double between 2020 and 2050, whereas the oldest old one –those aged over 80 years- should be multiplied by 5 in the same period (1). This demographic revolution has led to clinical, public health, policy, and individual interest regarding how to age “successfully”. The first key element in order to determine this “success” was established in 1948 when the World Health Organization (WHO) Member States adopted a new definition of health as “a state of complete physical, mental, and social well-being and not merely the absence of diseases” (2). However, despite this framework, the conception of aging was viewed as a period of degradation associated with disease and dependency, where little attention was given to people with healthy trajectories.
In 1961, the introduction of the term “Successful Aging” (SA) induced a fundamental shift, even though the consensus over the definition of this new concept and the way to measure it was (and to a certain extent still is) far from being reached (3). Actually, the word “successfully” is commonly used in the literature as a universal reference term for older people with healthy trajectories. Moreover, this concept brought a step that fostered the development of a positive view of aging and promoted research in order to demonstrate a possibly high level of functioning across several domains in old age. Consequently, different technical terms have emerged. These terms co-exist and compete to define this concept, including successful, healthy, active, well-being and others; terms that are often overlapping (4).
In 1987, Rowe and Kahn proposed in the normal category of aging, an additional distinction between usual and SA as nonpathological states. Eventually, ten years later, they summarized the central findings of that work, proposing the first model of “SA”, which was defined as “a low probability of disease and disability, high cognitive and physical functioning, as well as productive activity and activity involving relations with others” (5). This model has been essential in our understanding of the healthy aging process. Nonetheless, this model mainly relied on a biomedical approach underestimating the contribution of psychosocial, or personal perspectives on the aging process.
On the other hand, after Rowe and Kahn’s model of SA, numerous holistic theories have been proposed to improve the concept using different approaches involving environmental factors, security, and social active engagement models (6), until more recently ones based on subjective criteria, such as life-satisfaction or well-being (7, 8). These theories suggest a shift to a more holistic vision of SA (9, 10). In this vein, the WHO introduced in 2002 the concept of “active aging”, defined as: “Process of optimizing opportunities of health, participation, and security, seeking to improve life quality as people get older. Active aging consists of a health policy, influenced by gender and culture, and that is composed of behavioral, personal, physical, social, and economic determinants, as well as health and social service” (4).
Even though, more than half a century has passed since the introduction of the different technical terms of SA (“healthy”, “active”, “successful”, “well-being”, …), no universal operationalization or standardized definition has emerged (11). A variety of objective and subjective measures have been proposed in order to operationalize it (12) and several essential components have been identified, such as cognitive, physical, psychosocial, or environmental dimensions (13–15). Our literature review article aims to identify discrepancies and convergences between the main technical terms of SA through quantitative or qualitative or mixed methodology.

 

Methods

Search strategy

A literature review through PubMed, SCOPUS, PsycINFO, Psycarticles, Psychology and Behavioral Sciences Collection, Cochrane database, and clinicaltrials.gov databases was conducted. The comprehensive research strategy included six successful technical terms: “successful aging”, “healthy aging”, “active aging”, “aging well”, “self-perceived successful aging”, and “subjective well-being in late life”.
These terms were used in orthography conventions of both “aging” and “ageing”. In addition, where possible, some restrictions were used in the database such as “original articles” type of publication, “English” language, articles involving only “humans”, and the age of the participants “65 years and older” at the time of assessment of SA. This process was replicated where possible through the seven databases mentioned above by using the successful technical terms sequentially followed by the three keywords: “Definition” OR “concept” OR “determinant”. A wildcat operator, i.e. “*”, was inserted as a suffix to capture all permutations. The research included all the articles published before July 2019. A total of 1,057 articles were found, of which 650 were screened after deleting 407 duplicates.

Study inclusion

Peer-reviewed research articles on the SA concept, conducted through quantitative, qualitative, or mixed methodology in community-dwelling older adults, were included. When an author published several articles with the same techical term, the most relevant ones were taken into account according to the inclusion criteria. Included articles were then rated for relevance to our study objective.

Exclusion criteria

We excluded book reviews, short comments, letters, and papers which had a specialized focus solely on biology, physiology, immunology, genetics, laboratory or animal research, practical therapy, etc. Studies conducted in older adults with specific pathological conditions (e.g., HIV, frailty, cancer, Alzheimer’s disease) were excluded since the perspective of this review is the SA in the general older population.

Data extraction

The title (first) and abstract (second) of each article were reviewed in order to identify relevancy for full-text extraction. Forty-three articles were selected for full extraction (Figure 1).

Figure 1
Inclusion flowchart of the screening process for study inclusion

*Specific subject on biology, physiology, immunology, genetics, laboratory or animal research, practical therapy, odontology, nutrition, etc. †Specific pathological conditions e.g., HIV, frailty, cancer, Alzheimer’s disease.

Results

Included studies

The global search strategy identified 1,057 articles. After exclusion of the duplicates, the screening on title (n=650) and abstract (n=218) finally led to 43 studies that met inclusion criteria for full-text extraction (Figure 1). We distinguished 19 quantitative, 23 qualitative and 1 mixed-method studies that are summarized in tables 1 and 2 displaying: Authors, year, country, age population, study design (cross-sectional/longitudinal), sample size, models, operational definition, and main results.

Study characteristics

As may be seen in tables 1 and 2, the majority of the studies (19 of the 43 studies) were conducted in the United States. The sample size ranged widely from 15 to 17,886 and the age of participants from 15 to 102 years. Nearly half of the studies used quantitative methods and half qualitative methods (one study used mixed). Interestingly, the two thirds were published in the last ten years.

Table 1
Operationalization of SA and the Outcome Measures of Quantitative Studies

OR= odds ratio; IC= confidence interval; Non-standardized coefficients; HR: hazard ratio; SA=Successful Aging, QoL= quality of life; RR= relative risk; MCI= mild cognitive impairment; Receiver operating characteristic= ROC; AUC = Area Under the ROC Curve

Table 2
The Conception of SA by Integrating Older People’s Views in Qualitative Studies

 

A healthy aging trajectory could be more than only “successfully”?

Our literature review highlighted three main approaches of successful aging: 1) The biomedical models “focusing largely in terms of absence of disease, frailty or dependence and the continued maintenance of the physical and cognitive functions” as the main elements; 2) The psychosocial perspectives which emphasize the quality of life, engagement in social activities, and personal or community support; 3) The laypersons’ perspectives models which refers to people’s conceptions regarding what it means to age well.

Models mainly biomedical

The biomedical models of SA are mainly based on “the optimization of life expectancy, taking into account high physical and mental functional performance, mobility, and high levels of independence” (16, 17).
In this sense, an approach combining both mortality and morbidity would be relevant to define SA, such as the Disability-Free Life Expectancy, the Disability-Adjusted Life Years (DALYs) (18) or the Disability-Adjusted Life Expectancy (DALE) (19) (Table 3). Those global measures of population health provide a useful assessment of the impact of premature death and disability and other non-fatal health outcomes in the short and long term, but these indicators are probably not subtle enough to cover all the dimensions of SA.
This multidimensionality is proposed in the Rowe and Kahn’s model which is a reference in the literature of SA. It relies on disease and disability, cognitive and physical functioning, and participation in social activities (5). Even though this model has been widely applied, it has several important limitations. First of all, on “normal” aging (non-pathological) the model distinguishes “usual” or “successful” aging, excluding aging people with diseases (pathological aging) from SA. Considering SA as disease-free is quite unrealistic and too restrictive. Indeed, as recently underlined by the WHO (20), above a certain age category, most of older persons have one or more diseases, which, when well controlled, have no or little influence on their wellbeing. This approach which only considers two non-pathologic groups of older people, i.e. “usual” or “successful”, does not reflect the considerable heterogeneity among older adults (21). The group called “usual” (non-pathologic but at high risk) involves people presenting a normal decrease in physical, cognitive, and social functioning concerning age whereas the group called “successful” (at low risk and high functioning) refers to high levels of physiological and cognitive functioning. Finally, this model does not take into account the self-perceived dimension of SA, making it primarily medical and objective (22) (Table 3).

Table 3
Multiple models of technical terms in Successful Aging with respect to operationalizations and outcomes

Note: LY= year prevalence; Q= disability weight; PYLL= years of life lost due to premature death; BWB: Physical well-being; RMSEA= Root mean square error of approximation. *=Weights closer to 1 imply that a year spent in that condition is perceived as being more equivalent to death than to a state of health; †=Percentage of Participants Aging. Successfully by Definition of Successful Aging and Individual Characteristics for; ‡= These five domains are each individually well documented in the research literature; §= Percentages are weighted; **= p<0.001 for age groups. 1= Northern: Denmark, Sweden, Estonia; 2= Western: Austria, Belgium, France, Germany, Luxembourg, Holland /The Netherlands, Switzerland; 3= Southern: Italy, Spain; 4= Eastern: Czech Republic, Slovenia

 

Towards a more holistic approach: the introduction of psychosocial and environment factors

The current view relies on an holistic conception of SA that encompasses physical and cognitive functioning (23, 24), autonomy (25), independence (26), environment factors (living environment) (27), financial security (28), social, family and couple relationships (29, 30).
In this context, an initiative emerged from the 21st-century aging research agenda developed by the United Nations and the International Association of Gerontology and Geriatrics in 2004, the Global Research Network on Ageing (GARNet) (31) (Table 3). GARNet is a collaborative project of “aging-well” which uses the GARNet index that measures the five following domains: physical health and dependency; mental/cognitive effectiveness; social support resources; daily life activity (engagement), and material security. This initiative promotes the adoption of aging-well strategies that enable health and well-being, which is essential for extending life span and quality of life. Aging-well, it relies on individual behaviors and life-course material and social environments that limit functional decline (mainly caused by chronic conditions) to help older adults maintaining their independence and health (31). In this sense, it progressively decenters the approach from pure health; well-being becoming the central goal of the model along with quality of life, which increases the scope for enjoying the additional years of life. Showing high levels of well-being in older adults should not be overlooked since it is becoming an increasingly important goal for older adults themselves, caregivers, and also physicians (15). In fact, it has been shown that up to 45-50% of older people express satisfaction with their aging process even though they are poorly performing on objective measures (6). This finding can be seen at first sight as a paradox since with advancing age, older adults experience higher levels of well-being, until about 3-5 years near the end of life (26). Well-being is an integral component of adding life to years in an increasing longevity context, emphasizing the need for a multidimensional definition of SA (32).
In 2014, the WHO’s term proposed in a policy framework such as Active and Healthy Aging (AHA), as “the process of optimizing opportunities for health, participation and security in order to enhance quality of life as people age” (33) which became widely accepted, but without general agreement on what its application really means. So, the European Innovation Partnership on Active and Healthy Ageing (EIP on AHA) provided the use of operational tools to serve this purpose (34) with a focus on the relationship between activity and health. Since then, the concept was enriched with the addition of “active” as an extension of the concept for “healthy aging” being still more holistic and inclusive, encompassing different domains (e.g. social, economic, cultural, spiritual and civic affairs) (35) (Table 3). The AHA aims to lengthen life expectancy and delay functional dependency, thus preserving autonomy. The AHA working definition lists several steps to achieve these goals: 1) a multilevel approach of the AHA is necessary in order to determine the different items that must be considered; 2) it is necessary to find the tools that allow achieving the multilevel definition; 3) tools should be used in a single questionnaire; and 4) psychometric measurement capacities should be evaluated. However, at the same time, the AHA definition raises fundamental concerns both on structural and economic barriers. In addition, active aging and SA focuses on “youthful” activities that emphasize health and independence in a very ambitious way, which could lead to a form of stigmatization, i.e. “youthism”, if this level of activity is not reached. On the other hand, the economic downturn in different parts of the world could lead to material difficulties and with the resulting loss of opportunities for activity.
More recently, in 2016, the World Health Assembly reframed the components of healthy aging as part of the global strategy and plan of action on aging and health. This framework views healthy aging from a functional rather than a disease-based perspective as “the process of developing and maintaining functional ability that leads to well-being in old age” (20). Functional ability is determined by the person’s intrinsic capacity (i.e. all the individual physical and mental capacities that a person can draw on in daily life), the relevant environmental factors (i.e., all the resources or barriers that will determine whether a person can engage him/herself in activities or not) and the interaction between the two. Functional ability is defined as the health-related attributes that enable people to be and do what they have reason to value (i.e., meeting basic needs; learning, growing and making decisions; moving around; building and maintaining relationships; and contributing). Using the International Classification of Functioning, Disability and Health (ICF) (36) framework as background in order to facilitate the translation of the current theoretical model into practice, it is important to identify the inner nature of its constituting constructs, in particular, the constituent elements of the central construct of intrinsic capacity (i.e. locomotion, vitality, cognition, psychological, vision or hearing) (Table 3).to know where to observe, what to measure and how to monitor. Consequently, healthy aging shows the continuous interaction between intrinsic capacity of individuals in link with the environments they inhabit (supportive or barrier): appropriate and integrated care (technical and medical products, artificial replacements, transplants…), technical aids (auxiliary device, such as a walking stick, wheelchair…), social resources on which the older person can rely on, the use of technologies or support for multiple services (accessible stores, banks and professional services) (20, 37). The health policy of the Global Strategy and Action in this area is generally in the framework of the notion of age-friendly environments, involving both physical and social components (20).

Laypersons’ perspectives

Qualitative research contributed to improving the conception of SA by integrating older people’s views (38) which have essential implications of what individuals consider as SA for complementing traditional models (39), which are predominantly studied by models based on quanlitative approach.
Lay perspectives include a broad framework of criteria that combine basic resources (Table 2 and 3) (functioning (23), social health (40), financial security (41), family and intergenerational care (42) psychological factors (mental) (29), personal attitudinal (43), life satisfaction (35), positive outlook (44), self-consciousness (45), behavioral strategies (resilience (42), coping (44), contribution to life (26), accomplishments (29), productivity (35), learning new things (46), adaptation to an aging body (28) and beliefs (spirituality (27), having a sense of purpose (47), cultural variations (9), among others.
On the one hand, studies suggest that lay perspectives in SA give a great value to the importance of the psychological aspects of older adults, as accepting oneself, including the development of a realistic self-appraisal and a review of one’s past experiences “I’ve never felt more authentically me, ever, than I do right now. And it’s just so cool…” (45). On the other hand, this approach also focuses on social environments of older adults, the importance of active engagement with life and growth, including novel, productive, and social engagement, and the value of a positive attitude: “Keep your old friends, make some new ones, don’t isolate yourself” (45, 48). As a result of these model, the concept of SA is explored across cultures experiences and values that the population can express, as individuals provided with a conscience, language, and will (what is capable of value).
To illustrate the complementarity of older people’s perspectives with other traditional approaches of SA. A Dutch research on octogenarians with qualitative interviews compared the meaning of SA between two approaches; one based on laypersons’ perspectives and the other on the bio-psychosocial approach (major disability, cognitive impairment, depression, and regular social activities). According to this latter definition, only 10% of the participants were categorized as SA, compared to 81% of the participants as SA rated by laypersons’ perspectives definition. As a conclusion of this study, older persons view SA as a process of adaptation (e.g., thanks to strategy of coping or resilience) and maintain high levels of well-being despite disease or disability (42). Rather than a state of sole physical or mental efficiency, where the presence of a disease in old age excludes from successful aging. SA should also integrate laypersons’ perspectives, as recently recommended by the WHO (20), where healthy aging is based on what people have reason to value and not the absence of disease. According to this approach, more persons could be considered to be successfully aged.
An essential resource for both personal and community development is the aspects of sustainability, which promote a more dynamic process of well-being in aging, such as financial security, which allows the use of resources such as health services, social activity, and civic participation (49).
However, despite its increasing importance in the literature, limited evidence has been provided to assess how the views of laypeople on SA brings added value to the concept of SA.

 

Discussion

Our literature review aims to identify divergences and convergences from different technical terms of “successful aging” across quantitative and qualitative studies. This review confirms that since the initial coining of the term SA more than 50 years ago, the conceptualization and operationalization of the concept remains controversial and tricky to achieve. Many definitions of SA emerged and with them, multiple research methods, including unidimensional (14) or multidimensional (32) approaches, models based on objective or subjective (50)criteria, with qualitative or quantitative or mixed methodology, following a continuum (51) or through dichotomous profiles.
One of the lessons learned is the increasing importance given to the personal perspectives of the older persons. A recent review of operational definitions of SA reveals that there are more than twice as many studies that postulate operational definitions of SA as studies that examine lay perspectives of SA (52). As recommended in the Healthy Aging concept proposed by the WHO (20),the SA approach should be centered on what is important to the person and the ways (medical and environmental) to reach this goal. As they age, individual’s place a high value in the achievement of social goals, frequently related to family (partner, children and brothers/sisters) and leisure activities, or receiving emotional care (e.g. the care of the partner) (28, 43, 53, 54). In this sense, SA needs to be multi-dimensional and be seen as a continuum instead of dichotomized (successful versus unsuccessful) category, and needs to incorporate layperson’s perspectives for social significance, to be sensitive to differences in opportunities to age successfully and to variations in values between cultures (29, 55, 56).
This review also evidences the profound heterogeneity in the operationalization of the SA concept. The activity and social engagement elements (6) were identified as those reported most frequently. In addition, elements as economy and nature are absent in most conceptualizations of the SA. In this field, many authors addressed the topic of SA with their own outcome measures, assuming an adequate approach without much attempt at conceptual or theoretical definition. The SA models vary from pure biomedical (57, 58) (solely based on physical and cognitive parameters -e.g., studies on healthy life expectancy-) (59), to pure psychosocial (holistic conception –e.g., age-friendly environments-) or the lay models (older people’s views), while, some others, postulate intrinsic interactions among the different dimensions, which evidence the complexity of the term “successfully” in the aging process. Finally, another issue results from the fact that some parameters are used to define SA in some studies, whereas in others they are considered as outcomes. For instance, life satisfaction is assumed to be an essential predictor of SA while it is also defined as a significant outcome of SA (35).
This review has limitations. First, it was not possible to classify studies by technical term, due to the wide overlapping of the approaches used and the lack of clarity regarding the theoretical definitions, as mentioned above. We also limited our research after 65 years of age and only focused on the most frequently used models of the literature (limiting our research on six successful technical terms).
The main strength of our review is that it included both quantitative and qualitative studies. Considering such a range of studies allowed highlighting significant divergences between biomedical conceptualizations of SA and layperson’s perspectives approaches.

 

Conclusions

Healthy aging is an interrelated multidimensional process profoundly heterogeneous, with significant variations between individuals in the experiences lived. For healthy aging trajectories, an optimal approach should be one’s in terms of functional capacity, psychosocial abilities, environmental factors across the life course and also subjective assessments of one’s own criteria. This operationalized definition is crucial to provide pragmatic tools able to identify older adults with potential risk of “unsuccessful” aging and also ways to improve healthy aging trajectories of individuals. Therefore, the need for a consensual and operational definition is becoming a necessity not to say an emergency to face the public health, social, economic and individual challenges induced by our fast-aging populations.

 

Acknowledgments: The authors thank Coralie Thore for providing assistance with documentary support. AZR in appreciation of Mr. Pierre and Mrs. Aline Costet for your splendid hospitality during the summer of 2020.
Author Contributions: AZR and KP planned the review and search protocol; AZR wrote the paper review and conducted the data extraction. KP contributed to draft revisions. JFD and HA reviewed this paper.
Funding: The Fondation pour la Recherche Médicale (DOC20161136217 to AZR) supported this work. Funding has no role in the design, analysis, or preparation of this manuscript.
Ethical approval: Not required.
Data sharing statement: No additional data are available.

 

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