Functional disability among elderly Nigerians: results from the Ibadan Study of Ageing

Abstract

Functional disability is a common reason for loss of independence and need for informal care by elderly persons. There is little information on the profile of disability and the level of unmet need for care among elderly persons living in Sub-Sahara Africa. Using a multi-stage clustered sampling of households conducted in the Yoruba-speaking area of Nigeria (representing 22% of the national population), we assessed persons aged 65 years old and over (n = 2152) for disability in activities of daily living (ADL) and instrumental activities of daily living (IADL). Respondents were assessed for self-reports of physical health, for major depressive disorder, and for availability of informal care. The prevalence of any functional disability (defined as inability to independently perform any function) was 9.2% (s.e. 0.6). In logistic regression analysis, elevated risks of disability were associated with female gender, increasing age, and urban dwelling. Risks were also high for persons with chronic pain, those with poor self-reported overall health, and those with evidence of under nutrition. Disabled persons had poorer quality of life and were more likely to suffer from major depressive disorder. 19.8% of disabled elderly persons lacked any informal care and this unmet need for care increased the likelihood of having depression. The findings suggest a high burden of unmet need for care among a large section of disabled elderly persons in this African community undergoing demographic and social changes. Social factors relating to urbanization and poverty may be associated with both the occurrence of disability and inability to access informal care.

INTRODUCTION

The disablement process represents a distinct phase in the life of many elderly persons¹. Functional limitation is associated with loss of independence and with increased need for both formal and informal care ^{2 3}. Estimates of elderly persons with functional limitation are therefore vital for developing policies on aging that address provision of care, either from formal or informal sources. Unlike countries in Western Europe and North America,⁴, most developing countries, particularly those in sub-Sahara Africa, do not have estimates on which to base policy on aging even though the populations of their elderly persons (aged 60 years and over) are growing rapidly ⁵.

The profile of age-related disability in developing countries may be peculiar. For example, life expectancy in Nigeria is currently about 48 years for males and 50 years for females⁶. In such a setting, it is reasonable to believe that persons surviving to the age of 65 years and over may represent a constitutionally resilient sub-group. Indeed, while the healthy life expectancy (HALE) at birth in the country is 41 years for males and 42 years for females, males and females who live till the age of 60 years can expect to have another 9 and 10 years, respectively, of HALE.⁶ It is therefore plausible to speculate that the pattern and profile of disability that obtain among the elderly in developed countries may not apply to those living in developing countries.

Other than demographic features such as female sex and increasing age, ^{7 8} lifestyle features such as smoking and alcohol consumption, low education, low income, as well as urban dwelling have been associated with increased risk of disability among elderly persons^{7 9}. In many respects, these correlates of disability are particularly germane to sub-Saharan Africa in general and Nigeria in particular.¹⁰

In this paper, we report estimates of disability in a regionally representative sample of persons aged 65 years and over in Nigeria. We provide information on the socio-demographic correlates of disability as well as its impact on quality of life and psychological health of affected persons. Lastly, we present data on met and unmet need for informal care among disabled elderly persons.

METHODS

Sample

The Ibadan Study of Aging (ISA) is a community based survey of the mental and physical health status as well as of functioning and disability of elderly persons (aged 65 years and over). The survey was conducted in the Yoruba-speaking areas of Nigeria, consisting of eight contiguous states in the south-western (Lagos, Ogun, Osun, Oyo, Ondo, and Ekiti) and north-central regions (parts of Kogi and Kwara). These states account for about 22% of the Nigerian population (approximately, 25 million people). The survey was conducted between November 2003 and August 2004.

Nigeria is a country of about 130 million people. Persons aged 65 years and over constitute about 4.0 % of the population. The average national literacy rates are about 58% for women and 78% for men. The rates in the regions of this survey are higher: 89% and 95%, respectively, in the south-west and 64% and 86%, respectively in the north-central.¹¹ The south-west is predominantly Christian while the parts of the north-central where the survey was conducted have about equal proportions of Christians and Muslims. Most health statistics (e.g. infant mortality, vaccination coverage, use of contraception, fertility rate, etc.) tend to be better in the south-west compared to the rest of the country.¹¹ So, even though the cohort-specific life expectancies are not known, it is likely that, relative to the rest of the country, our sample of elderly may have a slightly higher live expectancy than national average.

Respondents were selected using a four-stage area probability sampling of households. In households with more than one eligible person (aged 65 years and fluent in the language of the study, Yoruba), the Kish table selection method was used to select one respondent ¹². When the primary respondent was either unavailable following repeated calls (5 repeated calls were made) or refused to participate, no replacement was made within the household. (Every call was made in person; telephone calls were not used). On the basis of this selection procedure, face-to face interviews were carried out on 2152 respondents, representing a response rate of 74.2%. Non-response was predominantly due to non-availability after repeated visits (14%), interviewers unable to trace the original address (4%), death (3%), and physical incapacitation (2%) and rarely due to refusal (2%). Respondents were informed about the study and provided consent, mostly verbal but sometimes signed, before interviews were conducted.

The survey was approved by the University of Ibadan/University College Hospital, Ibadan Joint Ethical Review Board.

Measures

Functional limitations were rated in two domains: 1) Activities of daily living (ADL) were assessed with the use of the Katz Index of Independence in Activities of Daily Living ¹³: bathing, dressing, toileting, arising and transferring, continence, and feeding. We changed the wording of the transfer item from “bed to chair” to “chair without arms or bed to standing”. 2) Instrumental activities of daily living (IADL) were assessed using a scale of seven items adapted from Nagi Physical Performance Scale and the Health Assessment Questionnaire ¹⁴: walking (around the house), climbing a flight of stairs, reaching above the head to carry something as heavy as 10 pounds, stooping, gripping small objects with hands, shopping, and activities such as sweeping the floor with a broom or pruning the grass around the yard. Items in both the Katz Index and the Nagi Scale were rated : 1) can do without difficulty, 2) can do with some difficulty, 3) can do only with assistance, or 4) unable to do. In this report, a rating of 3 or 4 was used to determine functional limitation on an item. Any such rating of at least one item within a domain (ADL or IADL) was regarded as impairment in that domain. Any respondent with a rating of impairment on any domain was asked whether they had someone who performed the role of a caregiver, that is, someone to help them in the area in which they required assistance. Responses were dichotomized to “yes” or “no”. A sub-group of 37 respondents was assessed twice, about 7 days apart, to determine the test-retest reliability of the disability items. Agreement was generally very good to excellent, ranging from a kappa of 0.65 to 1.0.

A checklist of chronic physical and pain conditions was included in the ISA. Respondents were asked if they had any chronic respiratory conditions (asthma, tuberculosis, other lung disease), digestive conditions (irritable bowel syndrome, ulcer), cardiovascular conditions (high blood pressure, heart disease, heart attack, stroke), cancer, diabetes, or epilepsy Respondents were asked whether they had experienced each of these symptom-based conditions in the previous 12 months. The checklist also ascertained the presence of any chronic pain (defined as persistent pain of 6 months duration). These included back or neck pain, chest pains, joint pains, frequent headaches, and a general category of persistent pain in any other body parts. Respondents were asked a range of lifestyle questions, including details about smoking and alcohol consumption. Nutritional status was assessed by measuring the mid-upper arm circumference (MUAC), a reliable and valid assessment of the nutritional status of elderly Africans^{15 16}. In this report, we have dichotomized the values to reflect a cut-off (on MUAC) that has been demonstrated to have a sensitivity of 86% in relation to a body mass index of 16 (which is indicative of severe undernutrition) in African samples ¹⁷. MUAC was assessed reliably in this survey: analysis of test-retest data on 25 respondents gave an intraclass coefficient value of .96 (95% CI .92 - .98)

Depression was assessed using the World Mental Health Survey version of the WHO Composite International Diagnostic Interview (WMH-CIDI; ¹⁸, a fully structured diagnostic interview. Diagnosis was based on the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) ¹⁹. CIDI organic exclusion rules were imposed in making the diagnosis of depression. We have used different versions of the CIDI, translated to Yoruba using standard iterative back translation method, in Nigeria ^20;21). WHO-CIDI Field Trials and other clinical calibration studies have shown these versions to have acceptable reliability and validity ¹⁸. Quality of life was evaluated in this survey with the brief version of the World Health Organization Quality of Life instrument (WHOQoL-Bref; ^22,23. The WHOQOL was developed as a cross-culturally applicable measure of subjective quality of life (²⁴. The WHOQoL-Bref has been shown to be a valid measure of subjective quality of life in the elderly ²⁵. The internal reliability of WHOQoL-Bref in this sample was excellent: Cronbach alpha = 0.86. The higher the score on the WHOQoL-Bref, the better the quality of life.

All the instruments were translated using iterative back-translation method. As part of the translation process, all the instruments used were subjected to cultural adaptation. Thus, for example, in describing 10 Ibs in the functional assessment, a tuber of yam (a local stable) of such weight was used.

In this report, we have examined the association of functional limitation with sociodemographic variables of age, sex, education, and economic status. Economic status was assessed by taking an inventory of household and personal items such as chairs, clock, bucket, radio, television set, fans, stove or cooker, car, telephone, etc. The list was composed of 21 such items. This is a standard and validated method of estimating economic wealth of elderly persons in low income settings ²⁶. Respondents' economic status is categorized by relating each respondent's total possessions to the median number of possessions of the entire sample. Thus, economic status is rated low if its ratio to the median is 0.5 or less, low-average if the ratio is 0.5 – 1.0, high-average if it is 1.0 – 2.0, and high if it is over 2.0. Residence was classified as rural (less than 12,000 households), semi-urban (12,000 – 20,000 households) and urban (greater than 20,000 households). Also, the quality of house floor was categorized into two (concrete vs. earth/mud) as another proxy of economic status.

Data analysis

In order to take account of the stratified multistage sampling procedure and the associated clustering, weights have been derived and applied to the rates presented in this report. The weights took account of the probability of selection as well as non-response. Also, post-stratification to the target sex and age range were made to adjust for differences between the sample and the total Nigerian population (according to 2000 United Nations projections). The weight so derived was normalized to reset the sum of weights back to the original sample size of 2152.

The analysis has taken account of the complex sample design and weighting. Thus, we used the jacknife replication method implemented with the STATA statistical package to estimate standard errors for proportions ²⁷. Demographic correlates were explored with logistic regression analysis ²⁸ and the estimates of standard errors of the Odds Ratio (OR's) obtained were made with the STATA. Chi square test and t-test were used to compare discrete and continuous variables, respectively. All probability tests were two-sided and all of the confidence intervals reported are adjusted for design effects.

RESULTS

Males accounted for 52.5% and females 47.5% of the sample. The mean age was 75.0 (9.2) years. Table 1 shows the prevalence of disability in the areas of activities of daily living (ADL), instrumental activities of daily living (IADL) or in either of the two areas. While 3.0% had disability in the performance of ADL, a much higher percentage of 9.1% was impaired in IADL. Females were more disabled, significantly so in the performance of IADL and overall. In all, disability increased with age such that compared with a prevalence of 4.0% for disability on IADL among those aged 65- 69 years, over one quarter of those aged 80 years and above were disabled. Persons who were currently married had lower rates of disability than those who were separated, divorced or widowed. Also, elderly persons resident in rural areas had the lowest rates of disability, semi-urban residents had intermediate rates, while those living in urban areas had the highest.

Table 1.

Prevalence of disability

	Weighted N	Disability on ADL1 % (95% CI)*	Disability on IADL2 % (95% CI)*
Entire Group	2152	3.0 (2.3, 3.9)	9.1 (7.9, 10.4)
Gender
Female	1157	3.4 (2.3, 5.0)	11.9 (9.7,14.5)
Male	995	2.7 (1.8, 4.0)	7.1 (5.7,8.8)
		x2=0.74;p=0.39	x2=10.68;p<0.01
Age, yr
65-69	747	1.1 (0.5,2.1)	4.0 (2.6,6.0)
70-74	483	1.9 (0.9,3.9)	6.3 (3.9,10.2)
75-79	300	3.9 (2.2,7.3)	9.9 (6.8,14.2)
80+	622	8.7 (6.3,11.9)	25.9 (22.5,30.0)
		x2=14.06;p=0.001	x2=30.07;p<0.001
Marital Status
Currently married	1127	2.2 (1.4, 3.3)	6.4 (4.9,8.2)
Separated/Divorced/Widowed	1025	4.4 (3.1, 6.2)	13.7 (10.9,17.0)
		x2=7.0;p<0.001	x2=15.52;p<0.001
Residence
Urban	529	4.7 (3.2, 6.8)	14.8 (11.1,19.4)
Semi-urban	900	2.5 (1.7, 3.5)	7.8 (6.3,9.5)
Rural	723	2.3 (1.1, 4.7)	6.2 (4.7,8.1)
		x2=2.79;p<0.07	x2=12.68;p<0.001
Years of Education
0	1142	2.5 (1.8, 3.4)	7.24 (5.9,8.8)
1-6	520	3.9 (2.3, 6.6)	11.2 (8.5,14.7)
7-12	298	3.0 (1.3, 6.9)	11.3 (7.5,16.7)
13+	172	3.7 (1.6,8.2)	10.88 (6.5,17.6)
		x2=0.78;p =0.503	x2=2.59;p =0.58

¹Activities of daily living, rated on the Katz scale.

²Instrumental activities of daily living, rated on the Nagi scale.

^*95% Confidence Interval

Logistic regression analyses in which sex and age were adjusted for confirmed the salience of residence for the occurrence of disability (Table 2). Compared to residents of rural areas, elderly residents of urban areas were two to three times more likely to have disability. Economic status, assessed using either ownership of personal and household items or the quality of house floor, did not bear any significant relationship to the occurrence of disability; nor did years of formal education.

Table 2.

Sociodemographic, health and lifestyle correlates of disability

	Disability on ADL1 OR (95% CI)3		Disability on IADL2 OR (95% CI)3
Marital Status
Currently Married	1	-	1	-
Separated/Divorced/Widowed	1.9 (0.97 – 3.89)		1.6 (0.76 - 3.45)
Economic status
High	1	-	1	-
High Average	0.6 (0.13 – 3.27)		1.4 (0.59 – 3.29)
Low Average	0.8 (0.18 – 3.56)		1.1 (0.54 – 2.19)
Low	0.7 (0.14 – 3.34)		0.8 (0.38 – 1.99)
House Floor
Concrete/Block	1	-	1	-
Mud/Earth	1.3 (0.67 – 2.53)		1.2 (0.84 – 1.69)
Site
Rural	1	-	1	-
Semi-Urban	1.0 (0.47 – 2.35)		1.2 (0.93 – 1.70)
Urban	2.2 (0.92 – 5.33)		3.0 (1.82 – 4.79)*
Years of Education
13+	1	-	1	-
7-12	0.8 (0.20 – 2.83)		1.0 (0.42 – 2.23)
1-6	1.0 (0.31 – 2.93)		1.0 (0.46 – 2.03)
0	0.6 (0.21 – 1.55)		0.6 (0.29 – 0.98)
Self reported chronic illness
Absent	1	-	1	-
Present	1.3 (0.70 - 2.46)		1.4 (0.95 – 1.93)
Self reported chronic pain
Absent	1	-	1	-
Present	3.9 (1.82 - 8.40)*		4.2 (2.81 – 6.42)*
Self reported overall health
Excellent/Good/Fair	1	-	1	-
Poor/Very Poor	4.8 (3.15 – 7.31)*		4.8 (3.15 – 7.31)*
Mid-arm circumference
≥ 22.1 cm	1		1
< 22.1 cm	1.6 (0.7 – 3.9)		1.9 (1.0 – 3.5) **
Lifetime Smoking
No	1	-	1	-
Yes	1.0 (0.57 – 1.78)		0.7 (0.50 – 1.09)
Lifetime Alcohol Use
No	1	-	1	-
Yes	0.7 (0.33 – 1.45)		0.7 (0.50 – 1.1)

¹Activities of daily living, rated on the Katz scale.

²Instrumental activities of daily living, rated on the Nagi scale.

³Odds Ratio (95% Confidence Interval), adjusted for sex and age. For Site, adjustment was made for sex, age, as well as years of education.

^*p < 0.001

^**p < 0.05

Self-reported chronic medical illness did not significantly increase the risk of disability. On the other hand, persons reporting persistent pain had a four-fold risk of being disabled compared to those with no persistent pain (Table 2). Poor perception of own health was also a significant predictor of functional disability, with those reporting that their health was poor or very poor having about five times the risk of disability compared to those who rated their health as excellent, good, or fair. Elderly persons with levels of mid-arm circumference indicative of severe malnutrition were at elevated risks to have functional limitation. This was significant for the groups with disability on instrumental activities of daily living. Neither a lifetime history of smoking or of alcohol use was associated with disability.

Persons with any form of disability had significant impairments in their quality of life. Table 3 shows that disability in activities of daily living or in instrumental activities of daily living was associated with poorer quality of life in all of the four domains of the WHOQoL-Bref. Persons with disability were more likely to have major depression in the prior 12 months but the association was only significant in regard to the activities of daily living.

Table 3.

Association of quality of life and major depressive disorder with disability

WHOQoL domains	Disability on ADL1		Disability on IADL2
	Yes	No	Yes	No
	mean scores (standard deviation)		mean scores (standard deviation)
Physical	9.2	14.9	10.6	15.3
	(3.78)	(3.53)	(3.75)	(3.32)
	t=−12.97; p<0.001		t=−18.77;p<0.001
Psychological	12.1	15.6	13.3	15.8
	(3.41)	(2.82)	(3.09)	(2.75)
	t=−8.64;p<0.001		t=−12.00;p<0.001
Social	10.9	13.6	11.5	13.8
	(4.44)	(3.86)	(4.30)	(3.72)
	t=−5.21;p<0.001		t=−8.06;p<0.001
Environmental	12.3	14.2	12.7	14.3
	(2.98)	(2.76)	(2.93)	(2.72)
	t=−5.46;p<0.001		t=−8.05;p<0.001
WHOQoL-Bref Total	66.9	88.3	72.4	89.5
	(17.5)	(15.3)	(16.52)	(14.69)
	t=−10.31;p<0.001		t=−15.24;p<0.001
MDD3, % yes (95% confidence interval)	15.1	7.5	12.2	7.3
	(8.8-24.8)	(6.1-9.2)	(7.0-20.4)	(5.7-9.3)
	χ2=6.6; p<0.02		χ2 =2.48;p = 0.12

Table compares the scores on WHOQoL-Bref among persons with and without disability.

¹Activities of daily living, rated on the Katz scale.

²Instrumental activities of daily living, rated on the Nagi scale.

³Major depressive disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition

Unmet need for care among disabled elderly

Persons requiring outside assistance in the performance of any ADL or IADL but who had no person to provide such assistance was regarded as having unmet need for care. For this classification, only informal care provision was considered. Formal care provision for disabled elderly persons living in the community is not available in Nigeria. Of the 263 persons who were classified as having any disability, 52 (19.8 %) did not have a caregiver to help in areas of limitation. Of these 52 persons, 61.5% were women, 38.5% were men. There were no significant demographic or social differences between those with met and those with unmet need for care. Also, residence did not differentiate the groups. However, persons with unmet need for care were significantly more likely to have a DSM-IV 12-month major depressive disorder than those whose needs were met: 17. 8 % (95% CI 7.0 – 38.4) in the former and 6.2% (95% CI 3.3 – 11.3) in the latter (χ² = 5.5, df. 1; p < 0.03).

DISCUSSION

In this first large-scale study of disability in a sub-Saharan African elderly population, we have shown that about 1 in 10 of elderly persons have some level of disability in either activities of daily living or in instrumental activities of daily living as to require assistance. Comparison with other studies is handicapped by differences in criterion definition and by sample profile. Studies using a less restrictive definition of disability, for example, in which disability is based on any level of difficulty in the performance of daily tasks, will be expected to report higher prevalence of disability. Also, when samples exclude institutionalized elderly persons as many studies do, the profile of disability will also be different. Institutional care of the elderly is very rare in Nigeria and our sample span the entire range of functional limitations obtainable in the population rather than exclusive of grossly disabled persons that might reside in nursing homes. Given these caveats, our rates are much lower than the 47% reported as having at least one disability in the US²⁹ but comparable to levels reported among elderly persons in Brazil⁹. Females were more likely to have functional disability than males. Also, increasing age was associated with increasing rates of disability. Both of these variables are often associated with the occurrence of disability in the literature ³⁰.

Multivariate logistic analyses controlling for the effects of gender and age confirmed the salience of residence for the occurrence of functional disability. As found in a Brazilian study, ⁹ persons living in urban areas had an elevated risk to be functionally disabled. Our observation, suggesting a graded elevation in risk from urban through semi-urban to rural residence would tend to indicate that differences in lifestyle were a likely basis of the association between residence and disability. However, the possibility also exists that disabled elders might have moved to their children residing in urban areas. Unlike the Brazilian study, we found no association between functional disability on the one hand and economic status or educational level on the other hand.

Not unexpectedly, the presence of chronic pain and self-reported poor or very poor overall health were associated with functional disability. Our failure to find an elevated risk among those who reported having a chronic medical condition might reflect a reporting bias: poor access to medical service as well as a high level of illiteracy would limit the number of elderly persons who might be aware of having a medical condition. ³¹. We observed that severe malnutrition was associated with disability. In an earlier study in rural Malawi, Chilima and Ismail observed a relationship between undernutrition and handgrip strength, psychomotor speed and coordination, mobility and ability to carry out activities of daily living independently. ¹⁶ In a cross-sectional study, it is impossible to determine the direction of causality between these variables. Nevertheless, the findings highlight the vulnerability of elderly persons with disability.

The impact of functional limitation is not inconsiderable. Persons with disability had poorer quality of life in every domain of the WHOQoL-Bref than those with no disability. The decrement in quality of life is not only in the physical domain, but also in those of environment, social relationships, and psychological well-being. The impairment of their psychological health is further indicated by the rates of DSM-IV major depression among elderly persons with disability, with the difference reaching statistical significance in the group with limitations in the performance of activities of daily living.

The observation that 19% of elderly persons with disability and therefore in need of assistance were unable to access such help is striking. It raises very serious questions about the availability of care to elderly persons in this society undergoing rapid social and economic changes. Traditionally, elderly persons in need of care have relied on family members to provide such care in African societies ³². Our findings demonstrate the urgency of the need for developing countries to become more aware of the consequences of the growth in the populations of their elderly. The consequences include not just the inevitable rise in the numbers of elderly persons who will become dependent on others for their daily needs but also the decline, for economic reasons (internal migration, increase in women working outside the home, etc,), in the availability of family members able and willing to provide such needs. Policies aimed at supporting family members to fulfill such roles remain the most viable and possibly more likely to be culturally acceptable rather than those centered around institutional or formal care.

One limitation of our study is the cross-sectional design. Even though we have found associations, our design does not allow us to determine the direction of causality. Also, we are unable to determine the extent to which the disability we observed was stable. We did not obtain information about duration and we could not assert that some of the disabilities were not transient in nature. Nevertheless, our findings do provide important information about the functional status of elderly persons living in a Sub-Saharan African country undergoing social changes of potential consequence to both the occurrence of disability and availability of informal care for those in need.