Interpreting excess mortality in a prevention trial for older adults

Abstract

Background: In a randomized trial evaluating preventive services for older adults excess mortality was observed in the treatment group. We examined four explanations: unbalance of baseline characteristics, unintended effects of the intervention, consequence of an autonomy intervention (including increased number of living wills in the treatment group), and chance. We focus here on the effects of the autonomy intervention.

Methods: Preparation of living wills in the treatment and control groups was compared both at baseline and follow-up. A linear predictor of mortality was used to identify participants at high risk of dying. Charts of these 200 participants were reviewed for evidence of serious medical events and resuscitation decisions. Rates of life-sustaining treatment were compared between treatment and controls using logistic regression.

Results: More living wills (65%) were noted for the treatment group than control group (47%) at follow-up. Thirty-six per cent of participants were identified as having a serious medical event; of these, participants in the treatment group were over twice as likely not to receive life-sustaining treatment.

Conclusions: Advance directives contributed to excess deaths, indicating the success of the autonomy intervention.