Who can decide? Prevalence of mental incapacity for treatment decisions in medical and surgical hospital inpatients in Ireland.

Background: The prevalence of mental incapacity for treatment decisions among medical and surgical hospital inpatients is poorly understood or not known in many countries, including Ireland.
Aim: To assess the prevalence of mental incapacity in hospital inpatients in Ireland.
Design: Cross-sectional observational study of mental incapacity for treatment decisions.
Methods: We assessed mental capacity in 300 randomly selected hospital inpatients in 2 general hospitals in Dublin (urban) and Portlaoise (rural), in Ireland, using the MacArthur Competence Assessment Tool for Treatment (MacCAT-T).
Results: Mean MacCAT-T score was 14.80 (SD: 8.40) out of a possible maximum of 20 (with a higher score indicating greater mental capacity). Over one quarter of participants (27.7%; n = 83) lacked the mental capacity for treatment decisions; 1.7% (n = 5) had partial capacity and 70.7% (n = 212) had full capacity. Scores for each of the four sub-scales of the MacCAT-T were generally consistent across the four key areas of understanding, appreciation, reasoning and expressing a choice.
Conclusions: Mental incapacity for treatment decisions is common in medical and surgical hospital inpatients in Ireland. This issue both merits and requires greater attention in clinical practice, research and legislation.