Loss of the ability to perform ADLs and mobility functions often leads to the loss of an older person’s ability to live independently.6
It was found that, in middle-aged subjects with arthritis, persistent difficulty in these tasks was substantially more likely to develop over 10 years of follow-up. The association between arthritis and functional difficulties was not explained after adjustment for other chronic conditions and other measures of baseline functioning. The majority of elderly people who lose the ability to independently perform ADL and mobility tasks first report difficulty with these tasks.8
Therefore, the results suggest that middle-aged people with symptomatic arthritis are at substantially higher risk for developing the common disabilities of later life at earlier ages and losing their independence at earlier ages.
Older people who become disabled generally follow one of two pathways.34,35
In the first pathway, generally referred to as the catastrophic pathway, disability develops suddenly. The most common causes of catastrophic disability are stroke and hip fracture. The second pathway, often referred to as the insidious pathway, is more common in elderly people. Elderly people who follow this pathway slowly accumulate functional deficits that, over time, become severe enough to result in the loss of independence. Generally, elderly people will first report difficulty in higher-level functional tasks such as walking long distances or doing heavy housework. This progresses to difficulty with more-basic functional tasks such as ALDs or walking short distances. Finally, the elderly person will lose the ability to perform these basic tasks without assistance and will become dependent on others.
Insidious disability, like most geriatric syndromes, is usually the result of multiple impairments that weaken the reserve capacity of an elderly person and lessen the ability to respond to stressors.36
In elderly people, arthritis, particularly osteoarthritis, is seldom the sole explanation for disability, but because it directly impairs the upper and lower extremity functions necessary for integrative tasks such as ADLs and mobility, it is not surprising that it is a frequent contributor to disability and an accelerator of its progression. Because arthritis is so common, even a modest effect on disability progression may have great public health effect.
Prior research has documented that arthritis is associated with disability in elderly people.13–17
In addition, short-term studies have demonstrated that older persons with arthritis are more likely to become disabled over a course of several years,18–21
although few studies have followed middle-aged subjects for long periods of time to examine whether they are at higher risk for developing the functional difficulties that lead to loss of independence in old age. Because of the decade-long follow-up of the current study, the results add to prior research by suggesting that arthritis significantly accelerates the development of the mobility and ADL difficulties that most commonly lead to loss of independence in elderly people.
In addition to the long follow-up, an important strength of this study was the ability to adjust for other determinants of disability such as other chronic conditions and baseline functional impairment. This decreases the likelihood that confounding factors explain the association between arthritis and later mobility and ADL difficulty, although several factors should be considered in interpreting the results.
First, the measure of arthritis was self-report of symptomatic arthritis. This measure is designed to capture the public health effect of symptomatic conditions bothersome enough to subjects to report symptoms to a physician or seek treatment. However, the self-report of arthritis does not necessarily correspond to the diagnostic criteria for rheumatological conditions. Although osteoarthritis is likely the most common etiology, given its high prevalence, the differential diagnosis of arthritis is quite broad. For example, other causes of arthritis include rheumatoid arthritis, gout, podiatric conditions, and nonspecific musculoskeletal conditions. These conditions may be highly variable in terms of their effect on functional difficulties, as well as the extent to which they can be remediated. Second, the measure of arthritis did not account for the severity of arthritis, and the effect of arthritis on task difficulty almost certainly varies with its severity. It is possible that this association is not linear and that there is a threshold at which more-severe arthritis results in functional difficulties. Third, it is likely that physical activity modulates the association between arthritis and functional difficulty. The measure of physical activity was probably not sensitive enough to test this hypothesis adequately. Finally, the outcome measure was persistent difficulty in mobility or ADLs rather than the need for assistance in these tasks, the traditional marker of loss of independent functioning in elderly people. As a result, an association between midlife arthritis and loss of independent functioning in later life has not been fully established, although the results make it highly likely that such an association exists. In noncatastrophic disability, difficulty in ADL and mobility function generally precedes dependence. Based on known trajectories of functioning in elderly people, it is unlikely that high rates of difficulty in functioning do not lead to high rates of dependence and loss of independence.8
In conclusion, it was found that middle-aged persons with arthritis were at higher risk for developing mobility and ADL difficulties that lead to loss of independence in late life. This finding highlights the need for efforts to develop treatments and interventions that prevent the disabling effect of arthritis.