Trouble in two or more everyday abilities was linked to higher dementia risk in older Taiwanese adults

Doctors usually look for dementia risk in memory tests. A team led from Chang Gung University in Taiwan asked whether a broader check-up of how well older people function day to day could also flag those more likely to develop dementia. In a national sample followed for nine years, people with problems in two or more basic abilities were diagnosed with dementia more often. The study is observational, so it shows a link, not a cause, and the authors describe the size of the link as mild.

The World Health Organization uses the term intrinsic capacity for the sum of a person's physical and mental abilities. It splits it into six areas, or "domains": thinking and memory (cognition), energy and nutrition (vitality), getting around (locomotion), seeing, hearing, and mood. The idea is that tracking these abilities, rather than single diseases, says more about how well someone will cope with ageing. Earlier studies had linked weak intrinsic capacity to frailty, disability and death, but few had looked at dementia.

What they did

• Who: 2,308 people aged 65 and over living at home, who took part in Taiwan's National Health Interview Survey in 2013. The original sample had 2,941 people; those who already had dementia or Parkinson's disease, had died in 2013, or had missing answers were left out.
• Measuring the six domains: thinking was checked with a standard short memory test (the Mini-Mental State Examination), with cut-offs adjusted for years of schooling. The other five were based on questions: poor appetite together with difficulty lifting 4.5 kg (vitality); difficulty walking 400 metres or climbing 10 steps without help (walking); difficulty seeing or hearing clearly even with glasses or a hearing aid; and a depression questionnaire (mood).
• Follow-up: new dementia diagnoses were taken from Taiwan's national health insurance records up to the end of 2022. Because people who die cannot later develop dementia, the team used a statistical method that treats death as a "competing" outcome. The results were adjusted for age, sex, education, marital status, smoking, high blood pressure, diabetes, stroke and heart disease.

What they found

• Problems were common. 28.4% of participants had a problem in one domain and 29.4% in two or more. Walking (31.1%), thinking (24.8%) and vision (23.0%) were the most frequent; vitality, as defined here, was rare (2.7%). Problems tended to come together: for every domain, most people with a problem there also had one in another domain.
• 358 people (15.5%) were diagnosed with dementia during the nine years.
• Two or more domains: higher risk. Compared with people with no problems, those with two or more had a 54% higher risk of a dementia diagnosis (subdistribution hazard ratio 1.54).
• One domain: no clear link. The estimate was 1.17, but it was not statistically significant.
• Checks held up. Leaving thinking out of the count, since it is the domain closest to dementia itself, gave a smaller but still higher risk (1.36). Ignoring diagnoses in the first two years, which might reflect dementia that was already starting, gave 1.63.

What to keep in mind

• Observational. The authors note that the design limits any causal reading. Early, unnoticed brain disease could cause both the everyday problems and the later dementia, although the two-year check argues somewhat against that.
• A mild link, no clear dose effect. The authors call the size of the association mild, and they did not find that each extra impaired domain added more risk step by step.
• Mostly self-reported. Apart from the memory test, all domains were based on people's own answers, which can be inaccurate.
• A healthier sample. The 449 people dropped for missing answers were older, less educated and in poorer health. So both how common the problems are and the strength of the link may be underestimated, and the authors advise care in generalising.
• Missing factors. The team had no data on APOE4, the best-known genetic risk factor for Alzheimer's disease, so it could not adjust for it. Dementia was identified from insurance claims, not by examining each person.
• Not yet a screening tool. The authors say more work is needed before recommending screening, for example to compare it with other dementia risk tools and to test whether helping people with several impaired abilities lowers their risk.

Why it matters

A short questionnaire about walking, seeing, hearing, mood and appetite, plus a quick memory test, is cheap and can be given in the community. This study suggests that older people who report problems in several of these areas at once may be a group worth watching for dementia. It also shows how common such multiple problems are: more than half of the participants with any impairment had more than one. Whether doing something about them changes dementia risk is the open question the authors want tested next.