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PREVALENCE AND DISTRIBUTION OF INTRINSIC CAPACITY AND ITS ASSOCIATIONS WITH HEALTH OUTCOMES IN OLDER PEOPLE: THE JOCKEY CLUB COMMUNITY EHEALTH CARE PROJECT IN HONG KONG

 

R. Yu1,2, G. Leung2, J. Leung3, C. Cheng2, S. Kong2, L.Y. Tam2, J. Woo1,2

 

1. Department of Medicine & Therapeutics, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China; 2. Jockey Club Institute of Ageing, The Chinese University of Hong Kong, Hong Kong, China; 3. Jockey Club Centre for Osteoporosis Care and Control, The Chinese University of Hong Kong, Hong Kong, China

Corresponding Author: Ruby Yu, The Chinese University of Hong Kong, Hong Kong, rubyyu@cuhk.edu.hk

J Frailty Aging 2022;in press
Published online March 2, 2022, http://dx.doi.org/10.14283/jfa.2022.19

 


Abstract

Objective: To determine the prevalence and distribution of intrinsic capacity (IC) impairments and examine their associations with health outcomes.
Methods: Community-dwelling people aged 60 years and older were interviewed at baseline and followed up for one to three years. IC domains including cognitive, locomotor, vitality, sensory (vision, hearing), and psychological capacities were assessed at baseline. Incident polypharmacy, incontinence, poor/fair self-rated health, and instrumental activities of daily living (IADL) difficulty were ascertained at each follow-up.
Findings: 10,007 participants were interviewed at baseline. Overall mean age was 75.7±7.9 years. At baseline, 85.3% had impairments in one or more IC domains, where cognitive capacity was the domain that was most frequently affected (71.3%). The prevalence of impairments in one or more domains increased with age (p<0.001) and was higher among women than men (p<0.001). Among the 1,601 participants who were interviewed at each follow-up, those with impairments in three or more domains had the greatest risk for the incidence of polypharmacy (adjusted OR 2.2, 95%CI 1.1-4.2), incontinence (adjusted OR 3.0, 95%CI 1.8-5.0), poor/fair self-rated health (adjusted OR 3.7, 95%CI 1.9-7.2), and IADL difficulty (adjusted OR 3.3, 95%CI 1.8-6.1) compared with those without IC impairments.
Conclusion: IC impairments are highly prevalent and those with IC impairments had increased risks of polypharmacy, incontinence, poor/fair self-rated health, and IADL difficulty. The findings could potentially lead to a refinement and the adoption of IC as a screening measure which could be served as a target of intervention in the care for older people.

Key words: ICOPE, intrinsic capacity, health outcomes, prevalence, incidence.


 

Introduction

The Life expectancy of older people has been increasing more rapidly than healthy life expectancy (1, 2), with the life extension of older people exposing to an elevated risk of ageing-related diseases and functional decline. This demographic shift brings forth substantial challenges for health and social care services as well as long-term care, partly as a result of the burden of functional loss and the dependency of older people.
To extend healthy life expectancy, the functional ability that enables all older people to be and to do what they have reason to value should be fostered, as recommended by the World Health Organization (WHO) in its ‘World report on ageing and health’ (3). This has led to an increasing understanding about the concept of intrinsic capacity (IC), which is the composite of all physical and mental capacities of an individual covering five domains including cognitive, locomotor, vitality, sensory, and psychological capacities (4). To facilitate the implementation of the concept of IC in the community, the WHO released the ‘Integrated care for older people (ICOPE): guidance for person-centred assessment and pathways in primary care (ICOPE Handbook)’, which outlines the steps to meet older people’s health and social care needs with an integrated approach (5). Following this, some studies have validated the concept of IC and showed the predictive ability of IC in estimating risk of dependency or mortality (6-10), while others have described the prevalence of IC impairments and demonstrated the feasibility of the ICOPE care pathways implementation (11-14). However, additional data from different populations across cultural settings is needed.
Hong Kong has attained the world’s highest life expectancy (15), with particular features that increase the complexity of care for older people including the high or rising number of people with frailty, chronic conditions, disability etc (16-18). Therefore, there is a pressing need to promote the concept of IC into the community, which would bring person-centred assessments and pathways for older people to the forefront. Using data collected from the longitudinal survey of the Jockey Club Community eHealth Care Project, the primary objective of this study was to determine the prevalence and distribution of IC impairments. The secondary objective was to examine the longitudinal associations of the number of impaired IC domains with the incidence of polypharmacy, incontinence, poor/fair self-rated health, and instrumental activities of daily living (IADL) difficulty among community-dwelling older Chinese people. We hypothesized that IC impairments would be associated with higher risks of incident polypharmacy, incontinence, poor/fair self-rated health, and IADL difficulty.

 

Methods

Study design and participants

The current study is part of a larger community primary care project, the Jockey Club Community eHealth Care Project which is initiated and supported by the Hong Kong Jockey Club Charities Trust. The project was designed to apply digital technologies to empower older people in health management and to promote integrated care and primary health services that are responsive to the needs of older people in Hong Kong. The project is conducted in phases (phase 1: 2016-2020 and phase 2: 2020-2022, the latter of which is currently still ongoing). The project services include (a) a longitudinal survey to identify the health and social care needs of older people in the community; (b) regular calls and outreach visits for a target group identified with needs, and (c) center-based activities that can help provide benefits for healthy ageing.
In phase 1, participants were recruited from 80 community elderly centres across 18 districts in Hong Kong. The sampling frame was based on a list of elderly centres within the Social Welfare Department of approximately 250 elderly centres in Hong Kong (19). A total of 80 centres were selected, including 19 (24%) centres in Hong Kong Island, 26 (33%) centres in Kowloon, and 35 (44%) centres in the New Territories, which was set to match with the proportions of older people aged 60 years or older residing in Hong Kong Island (20%), Kowloon (37%), and the New Territories (43%) according to the results of the 2011 Population Census (20). The eligibility criteria of participants were aged 60 years and older and community-dwelling at the time of the baseline assessment.
The longitudinal survey was carried out in elderly centres over four waves, starting in 2016/2017 (wave 1), 2017/2018 (wave 2), 2018/2019 (wave 3), and 2019/2020 (wave 4). The initial sample recruited at wave 1 consisted of 2,498 older people. They were renamed as core participants to distinguish them as the core element of the continuing project sample. The additional samples recruited at wave 2 and wave 3 consisted of 1,878 and 5,631 older people, respectively. The total sample recruited in phase 1 of the project consisted of 10,007 older people. An overview of the participants studied in phase 1 is provided in Figure 1.

Measurements

Each participant was given a tablet computer to complete the survey in small groups of six to eight. Designated staff members of the respective elderly centres were trained to guide the participants to finish the survey, which covered sociodemographic factors, medical history, IC, medications, incontinence, self-rated health, IADL difficulty, and use of health services, the latter of which is not evaluated in the present study.

Figure 1. Flow chart of the participants

Total number of participants (N): 10,007 = initial sample (n=2,498) + additional sample 1 (n=1,878) + additional sample 2 (n=5,631)

 

Sociodemographic factors and medical history

Age, gender, education level (‘no formal schooling/primary/secondary/tertiary’), marital status (‘single,/widowed/divorced/separated/married’), and living arrangement (‘living alone/living with others’) were assessed. Perceived disposable income was assessed by asking the participants ‘do you feel that you have adequate money these days?’ The possible responses were (‘very inadequate/inadequate/just right/adequate/very adequate’). Medical history of hypertension, diabetes, high cholesterol, heart diseases, stroke, chronic obstructive pulmonary disease, and renal diseases was also obtained.

Intrinsic capacity

Five IC domains were assessed: cognitive, locomotor, vitality, sensory (vision and hearing), and psychological capacities. For each domain, a threshold was applied to determine whether the participant has experienced impaired capacity.
• Cognitive capacity was assessed with the 5-item Abbreviated Memory Inventory for Chinese (AMIC). The questions were ‘do you always forget where things are placed?’, ‘are you always unable to recall the names of good friends?’, ‘are you always unable to follow and recall conversation?’, ‘are you always unable to find the right word to express yourself?’, and ‘do you consider your own memory to be worse when compared with others of a similar age?’. The total AMIC score ranges from 0 to 5, with 1 point for each item. Scores of ≥3 indicated greater risk of having mild cognitive impairment (21). In this study, those who scored ≥3 were considered as having an impairment in the cognitive domain.
• Locomotor capacity was assessed with item 2 ‘resistance: do you have any difficulty walking up 10 steps alone without resting and without aids?’ (‘yes/no’) and item 3 ‘ambulation: do you have any difficulty walking several hundred yards alone and without aids?’ (‘yes/no’) of the 5-item FRAIL scale (22-24). These two items were selected for their relevancy to mobility. Those who answered ‘yes’ to any of the two items were considered as having an impairment in the locomotor domain.
• Vitality was assessed by asking the participants ‘do you have any weight loss of ≥5% within the past 6 months?’ (‘yes/no’). Those who answered ‘yes’ were considered as having an impairment in the vitality domain.
• Sensory capacity (vision) was assessed using a similar item as described in the ICOPE Handbook ‘do you see things clearly?’ (‘very poor/poor/not too well/fair/good/very good’). Those who answered ‘very poor/poor/not too well’ were classified as having an impairment in the sensory (vision) domain.
• Sensory capacity (hearing) was assessed using a single question: ‘do you hear things clearly?’ (‘very poor/poor/not too well/fair/good/very good’). Those who answered ‘very poor/poor/not too well’ were classified as having an impairment in the sensory (hearing) domain.
• Psychological capacity was assessed with three questions capturing evaluative well-being ‘are you satisfied with your life?’ (‘yes/no’), hedonic well-being ‘are you happy with your life?’ (a Likert scale from 0 to 8, with 0 being the most unhappy and 8 being the happiest), and eudemonic well-being ‘do you find purpose or meaning in your life?’ (‘yes/no’) (25). Those who answered ‘no’ for evaluate or eudemonic well-being or scored ≤3 (the lowest quartile) for hedonic well-being were considered as having an impairment in the psychological domain.

Health outcomes

The number of prescribed medications was based on a single question ‘how many medications prescribed by the doctor are you taking?’ (‘0/1-4/≥5’). Polypharmacy was defined as regular use of five or more medications. Incontinence was assessed by asking the participants ‘do you have problems with incontinence (urinary, fecal, or both)?’ (‘yes/no’). Self-rated health was assessed using a single question ‘how would you rate your health in general at the present time?’ (‘poor/fair/good/very good/excellent’). In the analysis, those who answered ‘poor/fair’ were classified as having poor/fair self-rated health. IADL difficulty was assessed using five selected items extracted from the Lawton IADL scale (26-28). Participants were asked if they were able to complete five tasks either independently, with occasional help, or whether they were unable to do any of the tasks in the past three months. The tasks included use of telephone, transportation, shopping, meal preparation, and money management. A modified rating scale was used: a score of 1 would be obtained if the participant was independent with each of the task, a score of 2 if help was needed to complete the task, and a score of 3 if the participant was unable to complete the task. Those who scored 2 or 3 in any of the items were classified as having IADL difficulty.

Statistical analysis

The prevalence of IC impairments overall and in its domains were compared across age groups and between men and women, using chi-squared test. Univariate and multivariate logistic regression models were used to examine the associations of the number of impaired IC domains at baseline with the incidence of polypharmacy, incontinence, poor/fair self-rated health, and IADL difficulty at the 3-year follow-up. The number of impaired IC domains ranged from 0 to 6, with 0 representing no impairment in IC and 6 representing impairments in all IC domains. For this analysis, we combined the participants with impairments in three or more domains due to the limited number of participants in the respective groups, and participants without IC impairments were used as the reference group. For each outcome, the respective prevalence conditions were excluded. Progressive models were used as follows: crude mode, no adjustment; model 1, adjustment for age; model 2, further adjustment for gender, education level, marital status, and perceived disposable income; and model 3, further adjustment for chronic diseases. Statistical analyses were performed using the statistical package SPSS version 26 (SPSS, Inc., Chicago, IL, USA). A P value of less than 0.05 was considered statistically significant.

 

Results

The baseline characteristics of the 10,007 participants are presented in Table 1. The mean age was 75.7±7.9 years, 79.2% were women, 69.3% had primary education or below, 53.3% were non-married, 34.3% were living alone, 20.6% reported their income as inadequate/very inadequate, 20.3% met criteria for polypharmacy, 37.3% had incontinence, 66.9% had poor/fair self-rated health, and 25.6% had IADL difficulty. Among the 2,498 core participants, 1,601 (64.1%) were interviewed at each follow-up. Compared to those who were interviewed, those who were lost to follow-up were older, were more likely to have lower level of educational attainment, be non-married, be living alone, report their income as inadequate/very inadequate, and have impairments in three or more IC domains, polypharmacy, poor/fair self-rated health, and IADL difficulty at baseline (All p<0.05) (Supplementary Table 1).
The prevalence of IC impairments overall and in its domains, for the whole sample, by 5-year age group, and by gender are shown in Table 2. Among the 10,007 participants, 9,951 (99.4%) had complete data on each IC domain, of whom 8,492 (85.3%) had impairments in one or more IC domains. The prevalence of impairments in one or more domains increased with age from 76.9% at 60-64 years to 92.0% for those aged 85 years or older (p values for trend<0.001), and was higher among women (87.3%) than men (78.0%) (p<0.001). For each domain, the prevalence of impairments were 71.3% for cognitive, 45.8% for locomotor, 6.1% for vitality, 22.8% for sensory (vision), 19.1% for sensory (hearing), and 16.9% for psychological capacities. The prevalence of impairments in the cognitive, locomotor, and sensory domains increased linearly with age (all p values for trends<0.05), other than the psychological domain. By gender, while the prevalence of impairments in the cognitive, locomotor, and sensory (vision) domains were higher among women than men (all p<0.05), the prevalence of impairments in the sensory (hearing) and psychological domains were higher among men than women (all p<0.01). There were no significant differences in the vitality domain between men (6.5%) and women (6.0%) (Table 2).

Table 1. Baseline characteristics of the study population (N=10,007)

Abbreviations: SD = standard deviation; n = number of participants; IC = intrinsic capacity; IADL = instrumental activities of daily living. *Missing data: Educational level (n=2); Marital status (n=4); Living arrangement (n=8); Perceived disposable income (n=7); Number of impaired IC domains (n=56); Number of medications (n=135); Incontinence (n=24); Self-rated health (n=22); IADL difficulty (n=569). Percentages may not add up to 100% due to rounding.

 

Table 2. Prevalence of impairments in: (a) one or more intrinsic capacity domains; (b) the cognitive domain; (c) the locomotor domain; (d) the vitality domain; (e) the sensory (vision) domain; (f) the sensory (hearing) domain; (g) the psychological domain, by age group and gender (n=9,951)

Abbreviations: n = number of participants; IC = intrinsic capacity. 1P values for linear trend across age groups. 2P values for differences between men and women.

 

The longitudinal associations of the number of impaired IC domains with health outcomes of the core sample who were interviewed at each follow-up are shown in Table 3. There was a graded association between the number of impaired IC domains and the risks for the incidence of polypharmacy, incontinence, poor/fair self-rated health, and IADL difficulty. Compared with the participants without IC impairments (i.e. retained full capacity across all IC domains), those with impairments in three or more IC domains had the greatest risk for the incidence of polypharmacy (OR 2.3, 95%CI 1.3-4.1), incontinence (OR 3.3, 95%CI 2.1-5.3), poor/fair self-rated health (OR 4.4, 95%CI 2.4-8.2), and IADL difficulty (OR 3.5, 95%CI 2.0-6.4). The associations between the number of impaired IC domains and each of the outcomes remained significant in the group with three or more impaired domains after adjustment for age, gender, educational level, marital status, and perceived disposable income. Further adjustment for chronic diseases did not attenuate the associations, with adjusted OR (95%CI) being 2.2 (1.1-4.2) for polypharmacy, 3.0 (1.8-5.0) for incontinence, 3.7 (1.9-7.2) for poor/fair self-rated health, and 3.3 (1.8-6.1) for IADL difficulty, respectively.

Table 3. Associations of the number of impaired intrinsic capacity domains with incident polypharmacy, incontinence, poor/fair self-rated health, and instrumental activities of daily living difficulty at the 3-year follow-up (n=1,600)

Abbreviations: OR = odds ratio; CI = confidence intervals; IADL = instrumental activities of daily living; IC = intrinsic capacity. Reference group: Without IC impairments. No. of cases/no. at risk: Polypharmacy (n=177/1,235); Incontinence (n=313/1,088); Poor/fair self-rated health (n=252/559); IADL difficulty (n=190/1,132). Model 1: Adjusted for age. Model 2: Adjusted for age, gender, education level, marital status, and perceived disposable income. Model 3: Adjusted for age, gender, education level, marital status, perceived disposable income, and chronic diseases.

 

Discussion

This is one of the few studies reporting the prevalence and distribution of IC impairments, and how IC impairments is related to different health outcomes. Using longitudinal data of community-dwelling people aged 60 years and older, we found that 85.3% of the participants had experienced IC impairments, where cognitive capacity was the domain that was most frequently affected. We also found that the prevalence of IC impairments increased with increasing age, whereas women had a greater number of impaired IC domains than men. In addition, a grade association was found for increasing number of impaired IC domains in relations to the incidence of polypharmacy, incontinence, poor/fair self-rated health, and IADL difficulty at the three year follow-up.
Consistent with the Multidomain Alzheimer Preventive Trial (MAPT) (13) and Mexican Health and Aging Study (MHAS) (14), nearly 90% of the participants had impairments in one or more IC domains. The ICOPE pilot in China (69.1%) (12) and the 10/66 Dementia Research Group studies in Latin, America, India, and China (70.4%) (9) also reported a high percentage. Our findings highlight the need for increasing community capacity in providing assessments and interventions, as well as establishing referral networks for further clinical assessments and treatments of acute or severe conditions. These will enable integrated care for older people to be implemented, enable people to age in good health, and possibly alleviate the burden on the health and social care systems.
The prevalence of impairments in each IC domain are different across studies. For example, our findings show that cognitive (71.3%), locomotor (45.8%), and sensory (vision) capacities (22.8%) were the three domains more frequently affected. In the ICOPE pilot in China, the more frequently affected domains were cognitive capacity (46.8%), locomotor capacity (25.3%), and vitality (16.2%) (12), and in the MAPT, the corresponding domains were sensory (hearing) (56.2%), cognitive (52.2%), and psychological capacities (39.0%) (13), and in the MHAS, the corresponding domains were locomotor (47.6%), sensory (vision) (44.8%), and psychological capacities (43.1%) (14). Such variations may be partly explained by the use of different assessment questions. In the present study, some assessment tools were different from those suggested in the ICOPE Handbook. For the cognitive domain, only memory decline was assessed but not orientation in time and space. For the vitality domain, only weight loss was assessed but not appetite loss. For the sensory domain (hearing), it was assessed by a self-reported question instead of using a whisper test as suggested. For the psychological domain, instead of assessing depressive symptoms, we adopted a multiple approach to the measurement of subjective well-being (i.e. evaluative, hedonic, and eudemonic well-being), which is closely related to health, particularly at older ages (29). It is also worth noting that variations in the prevalence of impairments in each IC domain may reflect the heterogeneity in socioeconomic status, lifestyle behaviours, and environmental factors across populations. There is evidence that wealth, education, work, and nutritional status were positively associated with handgrip strength, an important measure of IC (30).
Consistent with the results of studies that have examined the prevalence of IC (full capacity) or IC impairments in its domains (3, 6, 7, 12, 31), our findings show that the prevalence of impairments in one or more domains increased with age and was higher among women than men. Of note, a substantial percentage of participants in each age group had impairments in the cognitive domain, even among those aged 60-64 (63.7%). This finding reiterates the need for attention to early intervention as memory complaints could be early signs of cognitive decline and possibly dementia in the future (32). In addition, there were gender differences in the prevalence of impairments in the cognitive, locomotor, sensory, and psychological domains. Such differences reaffirm that men and women experience vastly different health outcomes at the same age, and suggests that care planning for older people should pay attention to the heterogeneity and health disparities across gender.
Regarding the associations of IC impairments with health outcomes, we found a grade association between the number of impaired IC domains at baseline and the incidence of polypharmacy, incontinence, poor/fair self-rated health, and IADL difficulty at the 3-year follow-up. The results of the association between IC impairments and IADL difficulty are consistent with those reported from the English Longitudinal Study of Ageing (ELSA) (6), the Mr and MsOs (Hong Kong) study (7), and the 10/66 Dementia Research Group studies (9); in those studies IC had a direct relationship with incident IADL difficulty or care dependence. The findings reaffirm that the accumulation of impairments in IC domains can lead to a progressive functional decline.
The main strengths of our study include the large community-based samples and the detailed assessment of IC, polypharmacy, incontinence, self-rated health, and IADL difficulty. However, there are several limitations to be acknowledged. First, we did not include young old people (e.g. 50-59 years old) who might be a more appropriate target population for prevention. Second, compared to the gender distribution of older people in Hong Kong in 2016, our study population overrepresented women (79.2% vs. 52.5%) (33). Third, those who could not be followed up may have had different characteristics to those who were included in the longitudinal analysis. Fourth, some domains might deviate from the constructs indicated by the WHO, especially psychological domain, where we used subjective well-being questions encompassing evaluative, hedonic, and eudemonic well-being instead of depressive symptoms, which make comparisons across other population difficult. Fifth, the associations of IC impairments with health outcomes did not take into account the weights of each domain. Since each condition associated with IC impairments may not contribute equally to IC, further analysis should consider accounting for the weights of each domain in estimating IC. Sixth, we did not collect lifestyle and nutritional status, therefore, the potential confounding effects of these factors on the outcome measures could not be determined. Finally, we did not collect information regarding the onset of each chronic disease during the follow-ups; therefore, the impact of IC on the development of chronic diseases could not be determined.

 

Conclusion

While Hong Kong has the highest life expectancy in the world, IC impairments are highly prevalent and that those with IC impairments had increased risks of polypharmacy, incontinence, poor/fair self-rated health, and IADL difficulty. The findings have advanced our understanding of the conceptual foundations and measurement of IC and its associated health outcomes, supporting the WHO’s strategy to focus on optimizing or maintaining IC for achieving the goal of healthy ageing. In addition, the findings could potentially lead to a refinement and the adoption of IC as a screening measure which could be served as a target of intervention in the care for older people.

 

Conflicts of interest: None.

Ethical standard: The survey was approved by the Survey and Behavioral Ethics Committee of the Chinese University of Hong Kong (No. 126-16). All participants provided their informed consent to participate in the study.

Acknowledgements: The authors wish to thank the Hong Kong Jockey Club Charities Trust in supporting the project. We also wish to thank CUHK Jockey Club Institute of Ageing, Stanley Ho Big Data Decision Analytics Research Centre, and the Jockey Club School of Public Health and Primary Care of the Chinese University of Hong Kong, Senior Citizen Home Safety Association, all Non-Governmental Organizations, and the Jockey Club Community eHealth Care Project participants for their contribution to the project.

 

SUPPLEMENTARY MATERIAL

 

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