Background Advance Directives (ADs) are instruments in trying to improve quality of end-of-life care. The stability of preferences concerning end-of-life care says something about the validity of ADs.

Aim Investigate the stability of end-of-life treatment preferences of people owning an AD over a 4,5-year period.

Methods A longitudinal cohort study with a population of people owning different types of ADs, consisting of members of Right to Die-NL (NVVE, n = 4279) and the Christian orientated Nederlandse Patiënten Vereniging (NPV, n = 1014), answered written questionnaires between 2005 and 2010. We used hypothetical scenarios about cancer and dementia to assess preferences for continuing or forgoing resuscitation, mechanical ventilation, artificial nutrition and hydration, and antibiotics. Using a multi-state model we analysed whether health status and life events influenced changes in preferences.

Results From the NPV 24–33% changed their preferences from forgoing to continuing treatment or the other way around for the different treatments and scenarios. The part from the NVVE that changed ranged from 2–24%.

A person’s own health, a change in the health or the death of a loved one were associated with a change in preferences.

Discussion Preferences concerning continuing or forgoing treatment at the end of life stay stable for a majority of people owning ADs. Higher percentages of instability in the NPV group might be related to their AD (a will to live statement) neither clearly in- or excluding forgoing treatment at the end of life.

Conclusion The high stability found supports validity of Ads; on-going communication about their content is recommended.