Cognitive decline has been shown to result after hospital admission for a critical illness or an acute condition. But it has not been clear whether this is because the patients had symptoms of cognitive decline prior to the admission, or whether it is caused by being in hospital. In a new study, researchers at the University of Washington, Seattle, analyzed data from a study of older adults that involved cognitive testing. They also looked at data on hospitalizations in this group, to see if it was linked to cognitive decline. The study covered nearly 3,000 adults aged 65 or more who did not have dementia at the start of the study. 

During the follow up time of around six years, 1,287 participants were hospitalized for a non-critical illness and 41 participants for a critical illness. Among those who were never hospitalized, there were 146 cases of dementia. Among those with one or more hospitalizations for non-critical illness, there were 228 hospitalizations and there were five cases of dementia among those experiencing one or more critical illness hospitalizations during the study.

Those who were hospitalized for acute illness had lower cognitive scores than those not hospitalized during follow up. And those hospitalized for a non-critical illness had a 40% higher risk of dementia. The corresponding risk for those with a critical illness did not reach significance, maybe because of the smaller numbers in this group.

The researchers conclude that hospitalization is linked to cognitive decline, although the reason why is not clear. It may be that needing to be in hospital is a sign of cognitive decline that has not been diagnosed or that some factors linked to acute illness also make cognitive decline more likely. Some factors linked with hospitalization that may contribute to cognitive decline include: low oxygen levels in blood, delirium, inflammation and administration of medications like sedatives and analgesics. Therefore, we do not really know why admission to hospital carries a risk of cognitive decline among older people, but it is a question worth further exploration.

Source:

Ehlenback WJ et al Association between acute care and critical illness hospitalization and cognitive function in older adults Journal of the American Medical Association February 24 2010;303:763-770