Intensive care unit (ICU) patients are aging, and older age has been associated with higher mortality in ICU. As previous studies have reported that older age was also associated with less intensive treatment, we investigated the relationship between age, treatment intensity and mortality in medical ICU patients. Data were extracted from the administrative database of 18 medical ICUs. Patients with a unique medical ICU stay and a Simplified Acute Physiology Score II (without age-related points) >15 were included. Treatment intensity was described with a novel indicator, which is a four-group classification based upon the most frequent ICU procedures. The relationship between age, treatment intensity and hospital mortality was analyzed with the estimation of standardized mortality ratio in the four groups of treatment intensity. A total of 23,578 patients, including 3203 patients aged ≥80 years, were analyzed. Hospital mortality increased from 13 % for the younger patients (age < 40 years) to 38 % for the older patients (age ≥ 80 years), while Simplified Acute Physiology Score II (without age-related points) increased only from 36 (age < 40 years) to 43 (age ≥ 80). Hospital mortality increased with age in the four groups of treatment intensity. Standardized mortality ratio increased with age among the patients with less intensive treatment but was not associated with age among the patients with the highest treatment intensity. Our results support the fact that the increase in mortality with age among ICU patients is not related to an increase in severity. Using a new tool to estimate ICU treatment intensity, our study suggests that mortality of ICU patients increases with age whatever the treatment intensity is. Further investigations are required to determinate whether this increase in mortality among older ICU patients is related to undertreatment or to a lower efficiency of organ support treatment.

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