ADL disability is an age-related condition that leads to poor quality of life, increased health-related care costs, and increased mortality. The proportion of older adults are increasing worldwide, and it is therefore important both for society and the individual that research provide us with information about the process leading to ADL disability and how to identify persons at risk. The most effective design for following the aging process is found in population-based studies that include all older persons, both those living at home and those in residential care. This thesis uses data from three population based studies: the Kungsholmen Project (KP), the Nordanstig Project (NP) and the SNAC-N study. The aims of the thesis was to examine temporal changes in physical functioning in older adults, to identify underlying development of new disability and functional decline, as well as to explore geographical variation in physical functioning between urban and rural elderly habitats. We also wanted to describe the amount of informal and formal care in relation to levels of ADL disability. The ultimate aim was to identify factors suitable for prevention.
Study I: We I compared two populations of older adults, 75 years and older (the KP and the NP) from different living areas (urban and rural) and found differences in ADL disability, morbidity and disease patterns. The most common health problem in both areas was cardiovascular diseases (39.9% in the urban area and 45.2% in the rural area). There were great differences, urban vs rural, in the prevalence of stroke (7.4% vs 14.0%), diabetes mellitus (6.3% vs 16.1%), and Parkinson’s disease (1.0% vs 3.7%). Having two or more diseases vs. no disease was more common in the rural area than in the urban area, odds ratio (OR) = 1.9, 95% confidence interval (CI) = 1.4-2.4. Living area differences (urban vs rural) were found in population attributable risk (PAR) for disability due to stroke (5.6 vs 32.2), diabetes mellitus (1.2 vs 6.1), fractures (1.4 vs 10.7), and hearing impairment (8.7 vs 22.0).
Study II: Data were gathered from a population-based study of adults 60 years and older, the SNAC-Nordanstig (SNAC-N), and the study explored the association between ADL disability, muscle strength, disease severity and mortality. Upper and lower muscle strength decreased with increasing age, with a tendency for lower performance in women than in men. A significant association was found between ADL disability and having reduced lower muscle strength. Having an increased number of diseases increased the risk of being ADL disabled. Diseases with the greatest impact on ADL disability were musculoskeletal diseases, hypertension and dementia. ADL disability and being unable to perform the gait speed test were factors that increased the risk of death. Inability to perform the chair stand test or weaker grip strength increased the risk of death for men.
Study III: Data from two populations, 78 years and older, the NP (1995-1998) and the SNAC-N study (2001-2003), were used to study time trends in the prevalence of ADL disability and survival, comparing two cohorts. The prevalence of ADL disability was stable from 1995-1998 to 2001-2002 for men, while women became more disabled in ADL over the time period, (OR 2.36; CI 1.12-4.94). No significant difference was found in survival time between the cohorts in either ADL-disabled or non-disabled persons. There was a tendency for increased survival for non-disabled persons in the SNAC-N study compared with the NP, although it was not significant; this was particularly true for women. In general, women survived longer than men did regardless of whether they were ADL disabled or not.
Study IV: The aims were to examine the incidence of ADL disability, to explore whether being physically active earlier in life is a significant predictor of being disability free at follow-up, and to describe the amount of informal and formal care received in relation to ADL disability. Data were gathered from persons 78 years and older in the SNAC-N study. The incidence rates for men were almost the same in the age group 78-81 compared with the age group 84 years and older, 42.3 vs. 42.5/1000 person-years. For women the incidence rate for ADL disability increased significantly from the age group 78-81 to the age group 84 years and older, 20.8 vs. 118.3/1000 person-years. In the age group 78-81 years, being physically active earlier (aOR 6.2) and during the past 12 months before the baseline examination (aOR 2.9) were both significant preventive factors for ADL disability. The amount of both informal and formal care increased with the number of ADL activities the persons were dependent on and the amount of informal care was greater than the amount of formal care.
Conclusions: This thesis shows an increase in ADL disability due to increased age, and that women are more ADL disabled than men, but also shows how diseases affect ADL disability. The diseases that negatively affect ADL are often due to unhealthy lifestyle, e.g. physical inactivity, obesity and smoking, etc. The results show the importance of prevention of the factors that cause ADL disability, preferably already in midlife. The amount of both informal and formal care increased significantly with the number of ADL activities the persons required help with. Regarding prevention of becoming ADL disabled, it is of importance to find ways to postpone the onset of ADL disability so that we can live longer without disability.
Key words: ADL disability, informal and formal care, morbidity, mortality, older