Integration of an Objective Cognitive Assessment Into a Prognostic Index for 5-Year Mortality Prediction

Prognostic indices rarely include cognition. We determined if a comprehensive cognitive screen or brief individual items were associated with improved mortality predictions of a widely used prognostic index.

The National Social Life Health and Aging Project Wave 2, a nationally representative, cross-sectional, in-home survey conducted in 2010 to 2011 on 3,199 community-dwelling adults aged 60 to 99 years.

Cognition was measured using a Survey-Adapted Montreal Cognitive Assessment (MoCA-SA) grouped into three screened categories: screen normal (≥24 points), screen positive for mild cognitive impairment (18-23 points), and screen positive for dementia (<18 points). Single-item cognitive measures included clock-draw and five-word delayed recall. We constructed a modified Lee Prognostic Index (range = 0-18 points) based on age, behavior, function, and comorbidities shown to predict long-term mortality. We used logistic regression and the fraction of new information provided to determine if each cognitive measure improved the Lee index's 5-year mortality prediction.

The sample was 54% female and had a mean age of 72 years, MoCA-SA score of 22 (SD = 4.5), and Lee index of 7 (SD = 3). Regression analysis indicated the MoCA-SA modestly improved the Lee index's mortality prediction (P < .001; fraction of new information provided = 0.06); for low Lee index scores (<4 points), the absolute mortality rate difference was 7% by cognitive status; and for higher Lee index scores (4-7 points or 8-12 points), the absolute mortality rate difference was 15% by cognitive status. The clock-draw and delayed-recall items added similar value to mortality predictions as the longer MoCA-SA. Cognition had the third highest fraction of new information of all 13 Lee index items.

Incorporating a brief measure of cognition into a modified Lee index, even with single items, resulted in more accurate 5-year mortality risk predictions. Cognition should be included in prognostic calculators in older adults given its independent association with mortality risk. J Am Geriatr Soc 68:1796-1802, 2020.