Prevalence and Factors Associated with Impairment in Intrinsic Capacity among Community-Dwelling Older Adults: An Observational Study from South India

Background Intrinsic capacity (IC) is conceptualized by World Health Organization (WHO) with a focus on healthy aging. Identifying impairment could help in making a person-centred plan for the care of older adults. Objectives Establish the prevalence of IC among community-dwelling older adults age >60, the prevalence of impairment in each domain, and identify factors associated with an impairment in IC. Methods This cross-sectional observational study in the community setting included 1000 older adults aged 60 years and above in two-year study period. The 6 domains of IC including cognition, locomotor capacity, psychological, vitality, hearing, and vision were derived from the comprehensive geriatric assessment. The IC composite score was calculated based on these domains, and a higher IC score indicated greater IC. Results During the study period, 1000 older adults, with the median age of 66.5 (IQR-63-73) were included, and 629 (62.9%) were women. Only in 157 (15.7%) community-dwelling older adults, all 6 domains were intact. Impairment in one, two, and three domains was seen in 442 (42.2%), 305 (30.5%), and 91 (9.1%), respectively. The most prevalent impaired domain was locomotor (593, 59.3%), followed by vision (441, 44.1%), hearing (193, 19.3%), cognition (106, 10.6%), mood (38, 3.8%), and vitality (37, 3.7%). The factors associated with lower IC included increasing age (β-coefficient −0.01, 95% CI: −0.02 to −0.01, p value = 0.002), impaired activities of daily living (β-coefficient −0.13, 95% CI: −0.49 to −0.18, p value <0.001), and chronic neurologic illness (β-coefficient −0.10, 95% CI: −0.77 to −0.18, p value = 0.001). Conclusions In conclusion, we found that impairment in IC was frequent in community-dwelling older adults, and it is associated with age, presence of chronic neurologic illness, and declining functionality. The adoption of IC should be seen as an opportunity to disseminate geriatric care in our healthcare systems which lack the necessary attention to the needs of older persons.


Introduction
Advancing age of the global population is associated with increasing disability, which is a major challenge for the healthcare system [1]. Te World Health Organization (WHO) has conceptualized the health and healthcare of older adults around the concept of healthy ageing. Healthy ageing is defned as the process of developing and maintaining the functional ability that enables well-being in older age. In addition, it depends upon an individual's intrinsic capacity (IC), environment, and the interactions between the two [2]. Intrinsic capacity is the composite of all the physical and mental capacities individuals can draw upon at any point in their life [3]. It includes all the processes that help individuals to maintain independence.
Te fve diferent domains of IC proposed to operationalise the concept include cognition, mood, locomotion, vitality, and sensory domains (hearing and vision) [4]. Tese domains infuence each other and, in turn, are infuenced by environmental factors impacting the older person's functional ability. A continuous measure of IC and its trajectory in conjunction with the surrounding environment will help to track the functionality not only at the individual level but at the community level as well. Tis may, in turn, facilitate interventions to preserve IC and necessary changes in the environment, both at the individual and community level, to enhance and maintain the functional ability of older persons.
Multiple studies from India have reported frailty in hospital and community settings [5][6][7][8]. Few studies from India have recently reported on IC as well [9,10]. Tis study aimed to establish the prevalence of impaired IC among community-dwelling older adults aged ≥60 and the prevalence of impairment in each domain. We also intended to identify factors associated with an impairment in IC.

Materials and Methods
Te current study is a post hoc analysis of a cross-sectional study carried out in the community setting in a coastal city of South India. Four localities attached to a tertiary Care Medical college hospital in Mangalore, a coastal district in Karnataka, South India, were chosen for the main study. From each locality, 250 older adults were taken, giving a total sample size of 1000. Te study duration was two-year. Te study was initiated after obtaining ethical clearance from Institutional Ethics Committee. Community-dwelling older adults aged 60 years and above who consented to the evaluation were included, and people who were bed-bound with severe acute illness were excluded. A trained healthcare staf conducted a face-to-face interview to fll out a detailed questionnaire from the WHO Age friendly Primary Health Centres (PHC) toolkit consisting of seven parts. Te domains of IC, including cognition, locomotion, psychological, vision, hearing, and vitality, were derived from the CGA.
Te details included age, gender, socioeconomic status according to the modifed Kuppuswamy scale, marital status, and use of substances such as tobacco smoking and alcohol consumption. Height and weight were measured and body mass index (BMI) was measured as weight in kg divided by height squared in metres. Functional status was evaluated using basic activities of daily living (ADL) and instrumental activities of daily living (IADL). Geriatric syndromes included falls, urinary incontinence, constipation, and insomnia. Comorbidities, such as previous diagnosis of hypertension, diabetes, chronic respiratory disease, cardiovascular diseases, and chronic neurologic illness were assessed. Multimorbidity has been defned as presence of two or more comorbidities.

Domains of Intrinsic Capacity and
Scoring. Te domain of cognition was assessed using Hindi-Mental Status Examination (HMSE) [11,12]. Te locomotor capacity was evaluated using the timed-up and go-test [13,14]. Te psychological capacity was assessed using the Geriatric depression scale-15 (GDS 15) [15]. Te sensory domain included hearing assessment using a whisper test and vision using a screening question "Do you have any difculty in seeing a car from a long distance or reading or difculty in doing any of your daily activities because of your eyesight?." Te reply was considered positive if the subject replied as yes and negative if the answer was no. Vitality was assessed using body mass index (BMI).
A HMSE <24 was considered as impairment in cognitive domain. A TUG >13 seconds was used to identify impairment in locomotor domain. A GDS score ≥ 5 was considered abnormal. An inability to hear all three words in both the ears in a whisper test and a "yes" response for vision screen was abnormal. For vitality, a BMI < 18.5 kg/m 2 , which is the cut-of score for undernutrition in Asia Pacifc population [16], was used to identify impairment in vitality. Total maximum IC was 6 (one point for each domain). An impairment in even a single domain was considered as impaired IC. We did not do a priori sample size calculation. Continuous variables are described as mean, standard deviation or median, and interquartile range, and categorical variables are expressed as frequencies and percentages. Te association between categorical variables and IC score was analysed using Wilcoxon rank-sum test. For variables with more than two categories, Kruskal-Wallis test was used. If a signifcant main efect was found on the Kruskal-Wallis test, then a post-hoc analysis was performed using the Mann-Whitney U test to explain the signifcant main efect using Bonferroni correction. Complex linear regression was used to fnd the association of various factors with IC after adjustment for age and gender. Te results are presented as beta-coefcient and 95% confdence interval (CI). To fnd association between individual domains and factors, logistic regression was used. Te results are represented as odds ratio (OR) with 95% CI. A p value of <0.05 was considered statistically signifcant.

Results
A total of 1000 community-dwelling older adults were included in this study, and among them, 157 (15.7%) had intact IC ( Figure 1). Te median age (IQR) of the study population was 66.5 (63-73) years, and 629 (62.9%) were female. Table 1 describes the baseline characteristics, comorbidities, and geriatric syndromes. Only 30 and 59 participants were current smokers and consumed alcohol, respectively. Te ADL was impaired in 179 (17.9%) of the participants. More than two-thirds of the population (689, 70.2%) had a BMI more than 22.9 kg/m 2 .

Discussion
We report the prevalence of impairment in the IC domains and the factors associated with IC score of Indian community-dwelling older adults. Te main fndings of this study are (a) 15.7% have all IC domains intact, (b) IC declines with ageing, (c) increasing age, presence of chronic neurological illness, impaired ADL, and lower IADL score are associated with impaired IC, and (d) most impaired domains are locomotion and vision.
Te prevalence of impaired IC in our population was 84.3%, which was much higher than a community-based cross-sectional study from China, which reported a prevalence of 39.9% [17]. Tis diference could be due to the diferent tools used to measure various domains of IC as well as the diference in the defnition of impaired IC. Among the Chinese older adults, it was reported that locomotion was the most impaired domain (17.8%), followed by sensory (14.2%). We found that locomotion (59.3%) and vision (44.1%) are most commonly impaired domains, and the proportion was much higher. Also, the previous study was carried out at multiple sites across the country, and our study was carried out in a single community setting. Tese afected domains could be targets for intervention to preserve the autonomy of older adults, as impaired IC is associated with an increased risk of disability and falls, fractures, frailty, immobility and incident dependence, and death [17][18][19].
Of interest here is how the impairment in the domains of IC varies. A study which included data from Latin America, Indian, and China reported that there was considerable variation in the prevalence of individual capacities [18]. Te prevalence of maintained vitality varied between 66% and 98.7%, vision capacity and hearing capacity was between 59.8% and 93.5% and 76.9% and 96.8%, respectively. Cognitive capacity varied from 33.2% to 90.3%, and  psychological capacity was 62.0% to 98.5%. Interestingly the prevalence of full capacity also varied from 12.0% to 62.8%. Tese fndings highlight the importance of establishing region-specifc implementation of IC in the care needs of older adults.

Current Gerontology and Geriatrics Research
We found that increasing age is a risk factor for impairment in IC, which mirrors previous studies [17,18]. Similar to these studies, our study demonstrates an association between the presence of chronic neurologic disease with impaired IC. Morbidity (dementia, depression, and stroke) and disability were more common with declining IC [17]. However, we did not fnd any association between gender, education, marital status, substance abuse, and socioeconomic status. We also found that 84.3% of older adults had an impairment in one or more domains of IC, which is similar to previous studies (69-89%) [20][21][22].
Tis study reports on the status of IC in Indian community-dwelling people and the need for urgent intervention to prevent the consequences of impaired IC. Previous studies note that a decline in IC is independently associated with an increased risk of functional decline, falls, and mortality. Tis will lead to an increased burden on the healthcare system and a detrimental efect on individuals [18,21,23]. To identify these vulnerable older adults, the WHO proposed "Integrated Care for Older People (ICOPE)" could be implemented at the primary health care level. Tis will be essential for optimising the IC of older adults, helping them maintain their functional ability, and strengthening the concept of healthy ageing.
We acknowledge that the single community setting and the cross-sectional study design are major limitations. Due to the cross-sectional nature, we cannot establish a causal relation. Further longitudinal studies are urgently required to establish the relationship between the decline in IC and poor health-related outcomes, including mortality. We used a total composite score instead of a more appropriate weighted score. A study is required to establish a tool to    measure the IC using culturally appropriate tools and the cut-of for older Indian adults.

Conclusion
In conclusion, we found that decline in IC was frequent in community-dwelling older adults, and it is associated with age, presence of comorbidities, and declining functionality. Our research indicates that promoting IC to delay the decline in the functional capacity of older adults should focus on managing comorbidities and improving vision and locomotor domains. Te adoption of IC should be seen as an opportunity to disseminate geriatric care in our healthcare systems which lack the necessary attention to the needs of older persons.

Data Availability
Te de-identifed individual data are available on reasonable request from Dr Prabha Adikari by email Te data will be available starting from the date of publication onwards.

Disclosure
Abhijith Rarajam Rao and Mujtaba Waris are considered as frst authors.

Conflicts of Interest
Te authors declare that they have no conficts of interest.

Authors' Contributions
Abhijith Rajaram Rao contributed to manuscript writing, analysis, and interpretation and approved the fnal article. Mujtaba Waris carried out manuscript writing and approved the fnal article. Mamta Saini carried out manuscript writing and editing and approved the fnal article. Meenal Takral carried out manuscript writing and approved the fnal article. Karan Hegde carried out manuscript writing and approved the fnal article. Manjusha Bhagwasia performed data analyses and interpretation, editing, and approved the fnal article. Prabha Adhikari carried out study conception and design, and editing and approved the fnal article.