ReviewAging with multimorbidity: A systematic review of the literature
Highlights
► Multimorbidity affects more than half of the elderly population. ► Prevalence increases in very old persons, women and people from lower social classes. ► Very little is known about risk factors for multimorbidity (i.e., genetical or biological factors). ► Disability, poor quality of life, high health care utilization are consequences of multimorbidity. ► Data are insufficient for evidence-based care of patients with multimorbidity.
Introduction
Thousands of persons turn 65 years of age every day (Cohen, 2003, Kinsella and Velkoff, 2005). Life expectancy has already exceeded age 75 in 57 countries (World Health Organization, WHO, 2010), and it is expected to continue to rise (Oeppen and Vaupel, 2002). In the world, the proportion of 60+ year-old people has gradually increased from 8.1% in 1960 to 10% in 2000. Despite the worldwide aging phenomenon, data regarding health and time trends in the health of the elderly are still inadequate. What is certain is that over the last century, chronic health problems have replaced infectious diseases as the dominant health care burden, and almost all chronic conditions are strongly related to aging. Only in the last few years many health care planners and governments have becoming aware of this phenomenon and population-based studies regarding age-related chronic diseases have been implemented.
The majority of the available studies have focused on specific illnesses or on the coexistence of a relatively small number of diseases, such as cardiovascular diseases, diabetes, and cancer, rather than on the whole range of chronic morbidity affecting older persons. Few studies have investigated how diseases distribute or co-occur in the same individual, and most of them have used different approaches to address this issue (Gijsen et al., 2001). Two terms “comorbidity” and “multimorbidity” have been mostly used (Yancik et al., 2007). The term comorbidity was introduced 1970 and refers to the combination of additional diseases beyond an index disorder (Feinstein, 1970). This definition implies that the main interest is on an index condition and the possible effects of other disorders on the prognosis of this disease. In contrast, multimorbidity is defined as any co-occurrence of diseases in the same person indicating a shift of interest from a given index condition to individuals who suffer from multiple diseases (Batstra et al., 2002).
Different operational definitions of chronic multimorbidity are detectable in the literature. Indeed, multimorbidity has been addressed from three major perspectives which have led to three major operational definitions:
- 1.
Number (commonly two or three) of concurrent diseases in the same individual. This definition, which has been used mostly in epidemiological studies, includes both individuals who may live relatively unaffected by multimorbidity with the help of medications and those who face severe functional loss.
- 2.
Cumulative indices evaluating both number and severity of the concurrent diseases. This definition is very suitable in clinical studies where the major aim is to identify persons at risk for negative health outcomes and might benefit from specific interventions. Most used indices are: the Charlson Comorbidity Index (Charlson et al., 1987), the Index of Co-Existent Diseases (ICED) (Greenfield et al., 1993), and the Cumulative Illness Rating Scale (CIRS) (Linn et al., 1968).
- 3.
The simultaneous presence of diseases/symptoms, cognitive and physical functional limitations. In order to estimates trends of prevalence rates of elderly people with complex health problems that imply care needs involving several providers of both medical care and social services, studies address multimorbidity taking into account not only the cumulative effect of concurrent diseases, but also relevant factors such as symptoms, cognitive and physical dysfunctions, and psychosocial problems.
Given the complexity and heterogeneity of the health status of the elderly and the age-related pathologies, no single operational criteria will serve all research and clinical purposes effectively (Valderas et al., 2009, Fratiglioni et al., 2010). However, the common denominator of all the definitions is given by concurrence of several chronic diseases whose severity can be graded or not with different methods. For that reason, in this review, we will focus only on chronic multimorbidity based on clinical diagnoses and defined as the co-occurrence of multiple diseases in the same individual. Specific aims of this study are to summarise the scientific evidence cumulated in the last 20 years concerning occurrence, causes and consequences of multimorbidity in older persons and to compare the most relevant studies concerning models and quality of care for persons with multimorbidity.
Section snippets
Methods
We used MEDLINE/Pubmed database from January the 1st 1990 through November the 1st 2010 to identify the relevant studies. Criteria for inclusion were: original articles, English language, human subjects, and the availability of an abstract in Pubmed. We used two search strategies. First, the keywords ‘multimorbidity’, ‘multi-morbidity’, ‘multimorbidity AND comorbidity’, ‘multi-morbidity AND comorbidity’, ‘multimorbidity AND co-morbidity’ were included as search criterion in all fields. Second,
Results
The final number of articles included in the present review was 41, two published between 1990 and 2000 and 39 between 2001 and 2010 (Fig. 1).
Methodological issues
Several methodological problems emerged during the evaluation of the selected articles. First, age structure of the study population and selection of different care settings can have a large impact on study results. Second, information on health status including disease ascertainment was collected in different ways across studies, which leads to great variability in measuring the outcome of interest. Current methods include interviews, self-reports, medical record reviews, administrative
Conclusions
The main findings of this review can be summarized as follows; Multimorbidity affects more than half of the elderly population with increasing prevalence in very old persons, women and people from lower social classes. Very little is known about risk factors for multimorbidity, such as genetic background, biological causes, life styles, or environmental factors, whereas major consequences of multimorbidity are functional impairment, poor quality of life and high health care utilization and
Funding
This study was funded by research grants from the Loo and Hans Osterman Foundation. The authors’ work was independent of the funders.
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