Excess functional disability among demented subjects? Findings from the Canadian Study of Health and Aging

Dementia has been recognized as the strongest determinant for developing functional disability. However, dementia patients typically present with concomitant illness, thereby making difficult a determination of the fraction of disability due to dementia. The objective of this study was to estimate the prevalence of functional disability among demented and nondemented people and to estimate the excess disability in demented subjects net of conditions independently associated with disability in older people, using data on nearly 2,900 subjects from the clinical examination of the 1991 Canadian Study of Health and Aging. Unadjusted specific disability prevalence (in bathing, dressing, grooming, toileting and stool and urinary incontinence) is considerably greater among demented subjects than among cognitively normal or cognitively impaired but not demented subjects. After adjustments, specific disability in demented subjects is somewhat reduced in comparison to nondemented and cognitively impaired but not demented subjects. Thus, even when one considers the influence of a history of physical illnesses that typically result in disability, the link between disability and dementia is only marginally attenuated.