The delirium index (DI) is a valid measure of delirium severity. We proposed to describe longitudinal patterns of severity scores in older long-term care (LTC) residents.

A prospective cohort study of 280 residents in seven LTC facilities in Montreal and Quebec City, Canada, was conducted. DI, Barthel Index, Mini-Mental State Examination, Charlson Comorbidity Index, Cornell Scale for Depression in Dementia, dementia assessment by an MD, and prevalent or incident probable delirium defined according to the Confusion Assessment Method were completed at baseline. The DI was also assessed weekly for 6 months. Demographic characteristics were abstracted from resident charts. Cluster analysis for longitudinal data was used to describe longitudinal patterns of DI scores.

During the 24 weeks following enrolment, 28 (10.0%) of 280 residents who had prevalent delirium and 76 (27.1%) who had incident delirium were included in our analysis. Average observation period was 18.3 weeks. Four basic types of time evolution patterns were discovered: Improvement, Worsening, Fluctuating, and Steady, including 22%, 18%, 25%, and 35%, of the residents, respectively. With the exception of the Worsening pattern, the average trajectory was stabilized at the 4th week or earlier. Poor baseline cognitive and physical function and greater severity of delirium predicted worse trajectories over 24 weeks.

The longitudinal patterns of DI scores found in LTC residents resemble those found in an earlier study of delirium in acute care (AC) settings. However, compared to AC patients, LTC residents have a smaller DI variability over time, a less frequent Improvement pattern, and more frequent Worsening and Fluctuating patterns.