The European Journal of Public Health Advance Access originally published online on July 13, 2005
The European Journal of Public Health 2005 15(5):494-497; doi:10.1093/eurpub/cki015
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Health Inequalities |
Association between chronic diseases and disability in elderly subjects with low and high income: the Leiden 85-plus Study
Annetje Bootsma-van der Wiel1, Anton J.M. de Craen1, Eric Van Exel1, Peter W. Macfarlane2, Jacobijn Gussekloo1 and Rudi G.J. Westendorp1
1 Department of Gerontology and Geriatrics, Leiden University Medical Center, The Netherlands
2 Department of Medical Cardiology, Royal Infirmary, Glasgow, UK
Correspondence: Dr Anton J.M. de Craen, Dept. of Gerontology and Geriatrics, Leiden University Medical Centre, C2-R-133, PO Box 9600, 2300 RC Leiden, The Netherlands, tel: +31-71-526-6640, fax: +31-71-524-8159, e-mail: craen{at}lumc.nl
Received January 9, 2004, accepted May 4, 2004
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Abstract |
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Background: Disability in activities of daily living (ADL) might be more prevalent among elderly with low income due to higher prevalence of chronic diseases and impairments, as well as stronger associations of these factors with ADL-disability. Methods: In the Leiden 85-plus Study, we defined disability as being unable to perform one or more basic ADL activities. Presence of chronic diseases was obtained from medical records, impairments were assessed with performance-tests. Results: Elderly with low income had higher prevalence of ADL-disability (23% versus 12%; odds ratio 2.0; 95% confidence interval 1.3–3.2), higher prevalence of impairments and equal prevalence of chronic diseases, except for dementia and co-morbidity. Associations of these factors with ADL-disability were not stronger. Conclusions: We conclude that ADL-disability is more prevalent in elderly with low income. Neither prevalence of chronic diseases nor the association with disability could explain this.
Keywords: chronic diseases, disability, elderly, income
Current income level is a good measure for previously experienced cumulative deprivation.1 Compared with subjects with high income, subjects with low income have more chronic diseases and more disabilities in daily life,2–4 and have a shorter life expectancy.5 Furthermore, diseased persons with low income tend to present disease at a later and more severe stage,6 and have less access to therapeutic interventions.7–9 All these studies were in carried out in populations under the age of 85 years.
In the oldest old, income-related differences are smaller and the income–mortality gradient is less steep than in the working-age population.10 On the other hand, the oldest old frequently have several diseases and disabilities, and income-related differences might thus have a high impact on the population level. In the Leiden 85-plus Study, a population-based study in the oldest old, we investigated income-related differences in chronic diseases and disability. We hypothesized that among elderly with low income: (i) disability in basic activities of daily living (ADL) is more prevalent; (ii) prevalence of chronic diseases is higher; and (iii) the association between chronic diseases and disability is stronger, compared with individuals with a high income.
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Methods |
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The Leiden 85-plus Study is a population-based follow-up study of 599 subjects aged 85 years. There were no selection criteria on the basis of health or demographic characteristics. Sampling procedure and non-response analysis has been published previously.11 All participants were visited at their place of residence, where face-to-face interviews and performance tests were conducted and an electrocardiogram (ECG) was recorded. The medical history of all participants was obtained from their general practitioner or treating nursing home physician. Data on medication use were obtained from pharmacies. Cognitive function was assessed with the Mini-Mental State Examination (MMSE).12 All subjects gave informed consent.
In case of a severe cognitive impairment, defined as an MMSE score below 19 points, informed consent and information on income, education and disabilities in daily activities were obtained from a guardian. The Medical Ethical Committee of the Leiden University Medical Center approved the study.
Income
We asked standardized yes/no questions about state pension, other pensions and additional income per month, followed by an open question about the net amount for each category. To make income level of couples equivalent to that of single living persons, we multiplied household income for those living together by 0.7.13 Thirteen subjects provided incomplete data on income.
Disability
Disability in basic ADL was measured using the Groningen Activity Restriction Scale (GARS).14 The GARS assesses restrictions in competence in carrying out ADL. We defined disability as being unable to do any one of the following nine basic ADL independently: walk inside, get up out of bed, get into and out of a chair, visit the toilet, wash hands and face, wash body, dress and undress, eat and drink, and make breakfast.15
Chronic diseases
Presence of chronic diseases was obtained from subjects' general practitioners by a semi-structured interview and inspection of medical records. We have previously demonstrated that this method yields highly reliable results.16 For subjects living in a nursing home, the nursing home physician provided the necessary information. In addition, data on medication use were obtained from pharmacies and coded according to the Anatomical Therapeutic Chemical (ATC) classification.17
Apart from the medical records, diabetes, Parkinson's disease and chronic obstructive lung disease were also considered present when specific diabetes medication (ATC code A10), anti-Parkinson drugs (ATC code N04) or anti-asthmatics (ATC code R03) were prescribed. Arthritis was considered present when the medical history was positive for rheumatoid arthritis, osteo-arthritis or polymyalgia rheumatica. Furthermore, an ECG was recorded and transmitted to a central ECG core laboratory where conventional interpretation was provided automatically together with Minnesota codes.18 Q-wave myocardial infarction was defined as Minnesota code 1-1, 1-2 or 1-3.18 Undiagnosed myocardial infarction was defined as the presence of a Q-wave myocardial infarction on the ECG that was unknown to the subject's general practitioner or nursing home physician.
Data analysis
Proportions were compared with 
2-square tests. Odds ratios (OR) with corresponding 95% confidence intervals (95% CI) were obtained from logistic regression. Differences in the association between diseases and disability in low and high income groups were reported as P-values for interaction.
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Results |
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The participants, all aged exactly 85 years, were categorized into two strata of income dichotomized around the median net monthly income of 756 Euros. There were significantly more women in the low income group [212/294 (72%) versus 175/292 (60%); OR 1.7; 95% CI 1.2–2.5]. Disability in ADL was present in 101 participants (17%). Subjects with low income had a two-fold increased risk of being ADL-disabled compared with those with high income (OR 2.2; 95% CI 1.4–3.5). Twenty-one per cent of women were ADL-disabled compared with 10% of men (OR 2.4; 95% CI 1.4–4.1). However, the associations between income and ADL-disability were similar in women (OR 2.2; 95% CI 1.3–3.7) and men (OR 1.7; 95% CI 0.7–4.3).
Prevalences of various chronic diseases were equal for subjects with low and high income, except for dementia (OR 2.4; 95% CI 1.3–4.3) and multi-morbidity (OR 1.9; 95% CI 1.2–2.9) (table 1). Within strata of income, prevalences were similar in men and women, except for diabetes, which was more prevalent in low-income women.
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In both strata of income, stroke, Parkinson's disease and dementia were strongly associated with disability (table 2). The association of dementia was significantly lower in those with low income (OR 6.4, 95% CI 3.2–13; versus OR 22.7, 95% CI 7.8–66.4; P for interaction 0.05). None of the remainder of the associations between chronic diseases and disability was significantly different in elderly with low income compared with those with high income. All associations of chronic diseases and disability were similar for women and men (data not shown).
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Since neither the prevalence nor the association of chronic diseases with disability explained the two-fold increase in disability in those with low income, we performed various additional analyses. First, we explored whether underdiagnosis of diseases in persons with low income might explain our findings. A total of 99 participants had suffered a Q-wave myocardial infarction based on Minnesota coding of their ECG; 72 of these were undiagnosed (72/99; 73%). In participants with low income, prevalence of undiagnosed myocardial infarction was significantly higher than in participants with high income (16% versus 10%; P = 0.05). Omitting Minnesota code 1-3 as diagnostic for myocardial infarction did not alter these results. Secondly, we excluded persons with severe cognitive impairment [92 participants (16%) with MMSE score <19], because cognition is highly associated with disability. The prevalence of chronic diseases (excluding dementia) and the associations with disability as shown in table 2 were not different. Thirdly, we repeated all analyses for those whose only income was a state pension (96 participants; 16%) compared with those with an additional income (491 participants; 84%). The prevalence of chronic diseases and their association with disability had a similar pattern.
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Discussion |
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Subjects with low income more often had two or more chronic diseases than subjects with high income. Moreover, multi-morbidity also tended to be related more strongly with disability in subjects with low income, although this study probably lacked the power to demonstrate this statistically. Hence, our findings are in line with others who found that elderly persons with low income have a higher burden of co-morbid conditions,9,19 and thus indicate that we adequately dichotomized our subjects in a low and a high income group.
Another explanation for the discrepancy between the prevalence of chronic diseases and disabilities in different income groups is underdiagnosis or unawareness of disease among those with low income. We showed that a clinical diagnosis of myocardial infarction was equally present among those with high and low income, but that the prevalence of undiagnosed Q-wave infarctions was higher in those with low income. This is in line with the finding that chronic diseases can be present in the oldest old without a firm clinical diagnosis,20,21 and that clinical diseases are diagnosed at a later stage in people from low income groups.6,7
Neither gender nor the definition of income accounted for our findings. Moreover, severe cognitive impairment and presence of dementia also could not explain the difference between subjects with low and high income. We found dementia to be more prevalent in those with low income; however, the association of dementia with disability was significantly lower in those with low income. We think that those with high income might better hide their incompetence and are thus diagnosed as having dementia at a later and more severe state.
We conclude that among the oldest old, income-related differences in disability are still present. Clinically diagnosed chronic diseases could not explain the income-related difference in disability in the oldest old. Multi-morbidity and undiagnosed disease are possible explanations.
Key points
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Acknowledgments |
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We thank Perla J. Marang-van de Mheen for critical reading earlier versions of the manuscript. This study was partly funded by the Dutch Ministry of Health, Welfare and Sport.
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References |
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1 Wilkinson RG. Income inequality summarises the health burden of individual relative deprivation. BMJ 1997;314:1727.
2 Eachus J, Williams M, Chan P, et al. Deprivation and cause specific morbidity: evidence from the Somerset and Avon survey of health. BMJ 1996;312:287–92.
3 Kaplan GA. Maintenance of functioning in the elderly. Ann Epidemiol 1992;2:823–34.[Medline]
4 Mackenbach JP, Kunst AE, Cavelaars AE, et al. Socioeconomic inequalities in morbidity and mortality in western Europe. The EU Working Group on Socioeconomic Inequalities in Health. Lancet 1997;349:1655–9.[CrossRef][ISI][Medline]
5 Mackenbach JP. Income inequality and population health. BMJ 2002;324:1–2.
6 Fraser S, Bunce C, Wormald R, et al. Deprivation and late presentation of glaucoma: case–control study. BMJ 2001;322:639–43.
7 Latour-Perez J, Gutierrez-Vicen T, Lopez-Camps V, et al. Socioeconomic status and severity of illness on admission in acute myocardial infarction patients. Soc Sci Med 1996;43:1025–9.[CrossRef][ISI][Medline]
8 Alter DA, Naylor CD, Austin P, et al. Effects of socioeconomic status on access to invasive cardiac procedures and on mortality after acute myocardial infarction. N Engl J Med 1999;341:1359–67.
9 Philbin EF, McCullough PA, DiSalvo TG, et al. Underuse of invasive procedures among Medicaid patients with acute myocardial infarction. Am J Public Health 2001; 91:1082–8.[Abstract]
10 Backlund E, Sorlie PD, Johnson NJ. The shape of the relationship between income and mortality in the United States. Evidence from the National Longitudinal Mortality Study. Ann Epidemiol 1996;6:12–20.[CrossRef][ISI][Medline]
11 Bootsma-van der Wiel A, van Exel E, de Craen AJM, et al. A high response is not essential to prevent selection bias: results from the Leiden 85-plus Study. J Clin Epidemiol 2002;55:1119–25.[CrossRef][ISI][Medline]
12 Tombaugh TN, McIntyre NJ. The Mini-Mental State Examination: a comprehensive review. J Am Geriatr Soc 1992;40:922–35.[ISI][Medline]
13 van Rossum CT, van de MH, Witteman JC, et al. Socioeconomic status and aortic atherosclerosis in Dutch elderly people: the Rotterdam Study. Am J Epidemiol 1999;150:142–8.
14 Kempen GI, Miedema I, Ormel J, et al. The assessment of disability with the Groningen Activity Restriction Scale. Conceptual framework and psychometric properties. Soc Sci Med 1996;43:1601–10.[CrossRef][ISI][Medline]
15 Bootsma-van der Wiel A, Gussekloo J, de Craen AJM, et al. Disability in the oldest old: "can do" or "do do"? J Am Geriatr Soc 2001;49:909–14.[CrossRef][ISI][Medline]
16 Lagaay AM, van der Meij JC, Hijmans W. Validation of medical history taking as part of a population based survey in subjects aged 85 and over. BMJ 1992;304:1091–2.[ISI][Medline]
17 Guidelines for ATC Classification and DDD Assignment. Oslo, Norway: World Health Organization Collaborating Centre for Drug Statistics Methodology, 1996.
18 Macfarlane PW, Latif S. Automated serial ECG comparison based on the Minnesota code. J Electrocardiol 1996; 29 Suppl:29–34.
19 Turi ZG, Stone PH, Muller JE, et al. Implications for acute intervention related to time of hospital arrival in acute myocardial infarction. Am J Cardiol 1986;58:203–9.[CrossRef][ISI][Medline]
20 Hogan DB, Ebly EM, Fung TS. Disease, disability, and age in cognitively intact seniors: results from the Canadian Study of Health and Aging. J Gerontol A Biol Sci Med Sci 1999;54:M77–82.[Abstract]
21 Bloem BR, Gussekloo J, Lagaay AM, et al. Idiopathic senile gait disorders are signs of subclinical disease. J Am Geriatr Soc 2000;48:1098–101.[ISI][Medline]
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