Dementia in older people with intellectual disability: symptoms of physical and mental illness, and levels of adaptive behaviour.
Dementia in older adults with ID shows up as more illness, more irritability, and lower daily skills—screen all three areas.
01Research in Context
What this study did
The team looked at the adults with intellectual disability who were 60 years or older.
Half had dementia, half did not.
They counted chronic illnesses, mood changes, and scores on the Vineland Adaptive Behavior Scales.
What they found
The dementia group had more illnesses like heart disease and diabetes.
They also showed more irritability, aggression, and lower daily-living skills.
In short, dementia in this population looks like more sickness plus more challenging behavior.
How this fits with other research
Meyer (1999) later found the same link: physical illness predicts dementia in older adults with ID.
Drijver et al. (2025) now gives us a stronger tool, the DIAB, to catch the adaptive loss the 1997 paper first showed.
Balboni et al. (2020) seems to disagree: in severe ID, higher adaptive skills went hand-in-hand with more problem behavior.
The difference is age and setting: the 1997 elders lived at home, while the 2020 sample were younger and institutionalized.
Why it matters
If your client with ID is over 60 and suddenly more irritable or ill, screen for dementia.
Use the new DIAB to track tiny drops in self-care.
Share the pattern with doctors so treatable illnesses are not missed.
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02At a glance
03Original abstract
Detailed data on health and functional ability of 101 people with intellectual disability over 50 years of age are presented. Using a combination of informant interviewing, observation and measurement of cognitive change over a 3-year period, 12 of these individuals were identified as suffering from dementia. Their data are compared to those of the non-dementia sufferers. The people suffering from dementia had a greater number of chronic physical health problems and chronic disability resulting from physical health problems. Their capacity for self-directed activity was lower. The subjects had a reduced capacity to enjoy things, and were more irritable and more prone to violence. However, the outlook is somewhat different from a strategic perspective. The population of people with intellectual disability shows considerable epidemiological changes across the lifespan because of the effects of differential survival. The interaction of these factors tends to mask the impact of dementia-related skill loss in this population.
Journal of intellectual disability research : JIDR, 1997 · doi:10.1111/j.1365-2788.1997.tb00677.x