Correspondence: Dr Rowan Harwood, B Floor South Block, Queens Medical Centre, Nottingham NG7 2UH, UK. E-mail: rowan.harwood{at}mail.qmcuh-tr.trent.nhs.uk
Chronic and disabling diseases cannot be described adequately by diagnosis alone. The WHO published a classification of the consequences of disease over 20 years ago, which has recently been revised as the International Classification of Functioning, Disability and Health.1,2 This retains three fundamental levels of assessmentthe body level (anatomical or physiological problems; impairments), person level (activity limitations), and the person in context level (participation restrictions). Elderly people often have multiple pathologies and reduced physiological reserve, and experience a restrictive environment. Multi-level assessment across physical, psychological, and social domains is therefore particularly necessary, and forms the basis for comprehensive geriatric assessment.3
For the health services researcher multi-level classification indicates where interventions operate and suggests how they can be evaluated. Examples include prevention or cure of pathologies (e.g. polio, tuberculosis, stroke, or hip fracture), reversal of impairment (e.g. cataract surgery, arthroplasty, drugs for pain or heart failure), remediation of activity limitation (gait and balance training, continence promotion), or promoting participation (social and environmental modifications). Interventions at the more biological levels should give improvements at the functional and social levels. If they do not do this, the intervention is ineffective, a complication has arisen, or a rehabilitation opportunity has been missed.
Multi-dimensional health assessment is also valuable for public health and policy. The health economists holy grail of a single quantified health index remains elusive, not least because of the difficulty of the cognitive tasks involved in weighing-up and trading-off different aspects of health experience, and between-person variation in values and expectations. Instead the impact of disease and effect of therapies can be examined on a battery of appropriate measures. Many national surveys of disability prevalence have been performed, mainly in developed countries. Disabling diseases are not the preserve of the developed world, however. The natural history of human immunodeficiency virus infection is one of debility and disability before death. Many tropical infections (such as filariasis or river blindness) are predominantly disabling rather than killing. Trauma also represents a disproportionate burden on developing countries. Estimates from the WHO Global Burden of Disease project suggest that the prevalence of dependency (reliance on daily help from another person) is greatest in Sub-Saharan Africa, and in the rest of the developing world is about the same as in established market economies.4
The paper from India by Joshi and colleagues5 reminds us about demographic transition (India has a growing elderly population) and epidemiological transition (an increasing predominance of chronic disease). They find that problems such as chronic obstructive pulmonary disease, osteoarthritis, cataracts, neurological disorders, and dental problems are important determinants of health status in elderly Indians. The prevalence of many of these problems is remarkably similar to those in elderly Western populations, with a few exceptions (dementia, ischaemic heart disease, and osteoporotic fractures were not reported, whilst clinically diagnosed anaemia was very common).
Disability is strongly associated with age. Disability comes in degrees, and a key threshold is the requirement for frequent help from other people, beyond what would be expected by virtue of family or social ties (i.e. dependency). Over half the elderly Indians studied by Joshi et al. had this level of disability. On simple demographic grounds alone, the prevalence of dependency in India is likely to more than double over the next 50 years, and will increase as much as four- or fivefold elsewhere in the world.4 The major exception to this trend is in the developed countries, where most of the change has already occurred, and only relatively small further changes will be seen, but where most of the discussion of the phenomenon is centred.
At the same time the younger population is either declining or not increasing at a commensurate rate. This increases the so-called dependency ratiothe ratio of dependent people to workers. This will be seen in an extreme form in Eastern Europe, with very low fertility compounded by migration, but similar trends are also evident in Western Europe and Japan, China, and India.
There are numerous issues:
Difficulties in measuring important impairments, activity limitations, and other quality of life dimensions are reflected in the large numbers of scales available. Disability is a continuum, and setting thresholds for prevalence measurement is arbitrary. Standardization for surveys repeated over time and across countries is challenging.
Is disability an attribute of the individual afflicted, or the result of barriers raised by an unsympathetic society? The International Classification of Functioning, Disability and Health2 recognizes this dichotomy, and includes a section on contextual factors. Responses to disability must be both medical and societal.
Increasing dependency has important implications for gender equality. Women predominantly adopt caring rolesand consequently suffer a burden of physical and psychological ill-health, lost employment and social opportunities, and pension rights.
The increasing prevalence of dependency is taxing the health and social welfare systems of many economies, in terms of provision of services and funding pensions. The developing world faces the need for considerable extra infrastructure at the same time as increased expectations for education and leisure opportunities for younger people. Lower fertility means fewer young people to finance and service dependent people. This is the down-side of fertility control, necessary though that is in its own right. That only 64% of urban, and 22% of rural, Indians had sought medical treatment emphasizes the gap in current services, which must develop if unnecessary disability is to be averted.
Much disability is avoidableby preventing disabling diseases, medical and surgical interventions, and rehabilitation. To limit the social, economic, and humanitarian impact of population changes, the disability-avoidance agenda must be addressed in parallel with that of fertility control. In addition, non-professional (or informal) care-giving structures must be identified and supported, lest small shifts in levels of such support overwhelm statutory and professional services.
Researching health status and the impact of chronic disease is a relatively young science. Unfortunately, it has to compete for funds and minds with vibrant and productive laboratory sciences. Young science needs simple, descriptive research, and encouragement for researchers to move on to more substantial projects, a fact not always recognized by funding bodies and journals.
The developing world can learn from the experiences of the developed world, but this can only go so far. Empirical data on the health status of elderly people from around the world is needed also.
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2 World Health Organization. ICF. International Classification of Functioning, Disability and Health. Geneva: WHO, 2001. Also at: http://www3.who.int/icf/onlinebrowser/icf.cfm (accessed 20 July 2003).
3 American Geriatrics Society. Comprehensive Geriatric Assessment Position Paper. At: http://www.americangeriatrics.org/products/positionpapers/cga.shtml (accessed 20 July 2003).
4 Current and Future Caregiver Needs for People with Disabling Conditions. Long-term care series report. Geneva, WHO, 2002. Also at: http://www.who.int/ncd/long_term_care/long_term_care_publications.htm and http://www.who.int/ncd/long_term_care/country_profiles.htm (accessed 20 July 2003).
5 Joshi K, Kumar R, Avasthi A. Morbidity profile and its relationship with disability and psychological distress among elderly people in Northern India. Int J Epidemiol 2003;32:97887.