Life expectancy is increasing in Ireland, but whether this has resulted in healthier life years among the elderly and its impact (if any) on hospital services is unknown. The purpose of the study was to use routinely available data to explore the relationship of age and indicators of clinical complexity in acute hospitals over ten years. The study included all in-patients aged 65+ years from the Hospital In-Patient Enquiry (HIPE) discharged between 2005 and 2014. Indicators of complexity included the Charlson index, overall length of stay (LOS), intensive care unit LOS and deaths in hospital, analysed by the major clinical classification software (CCS). Over the period, the number and rate of admissions increased, especially among those aged 85+. Indicators of patient complexity increased and LOS decreased. In-hospital mortality decreased from 5.9% to 4.7%. Hospitals appear to be managing the emergency care of the older and more complex patient more efficiently and with better outcomes.