Feasibility of Physical Fitness Measurements in Older Adults With Intellectual Disabilities Within Two Large Cohort Studies: The HA-ID and IDS-TILDA Study.

The two cohorts could not be combined or compared statistically because of legal restrictions, so the differences between them, including the puzzling finding that the older Dutch group did better, cannot be pinned on any one cause. The two studies ran the tests differently. IDS-TILDA tested balance on one side only and allowed two grip strength attempts; HA-ID tested both sides and allowed three attempts. HA-ID also lowered the step height for people who could not reach it and counted an adjusted test as a success, while IDS-TILDA called it unsuccessful. The samples differed in age by about ten years (average 61 versus 71) and in how many could walk independently, and mobility status was missing for about a third of the HA-ID sample (61 of 180). This measures only whether a test could be completed to protocol. It does not show that the tests measure fitness well in this population, and the paper reports no reference values for interpreting the scores. Almost everyone lived in a central or community-based setting; only 25 of the 260 Irish participants and 1 of the 180 Dutch participants lived independently or with family, so other living situations are barely represented.

HA-ID was funded by the Academic Collaborative Research Center Healthy Ageing and Intellectual Disabilities, a consortium of three Dutch care organisations for people with intellectual disabilities (Abrona, Amarant and Ipse de Bruggen) working with the Department of General Practice, Intellectual Disability Medicine Research at Erasmus MC, University Medical Center Rotterdam. The paper states that the three care organisations had no involvement in data processing, analysis or writing the manuscript. IDS-TILDA is funded by the Health Research Board and the Department of Health, and the paper states those funders do not have access to any of the data. The authors declare no conflicts of interest.

Do not read the lower completion in IDS-TILDA as proof that those participants were less fit or less able. The two datasets could not be combined or compared statistically, and the studies used different protocols, so the gap may be measurement rather than ability. Feasibility also only says whether a test could be completed, not whether the scores it produces are valid.