Background: Patients treated in an intensive care unit (ICU) are seriously ill, have a high co‐morbidity, morbidity and mortality. ICUs are resource – demanding as they consume significant hospital resources for a minority of patients. The development of new medical procedures for critical care patients has over the years led to survival of larger numbers with more complex illnesses and extensive injuries. Improved survival rates lead to needs for outcome measures other than survival. The present study examines health‐related quality of life (HRQoL) and factors assumed to be important for the long term HRQoL for former ICU patients.

Methods: This is a multicenter cohort study of 980 adult patients admitted to one of three mixed medical‐surgical ICUs in Southern Sweden, during 2000 to 2004. The patients were studied at four different occasions after their critical illness: 6, 12, 24, and 36 months after discharge from the ICU and hospital. HRQoL was assessed by the EuroQol 5‐Dimensions (EQ‐5D) and Medical Outcome Short Form (SF‐36), sleep disturbances by the Basic Nordic Sleep questionnaire (BNSQ), and pre‐existing diseases was collected by self‐reported disease diagnosis. Data from a large public health survey (n=6093) of the county population were used as reference group.

Results: Compared with the age and sex adjusted general reference group the patients who had been in the ICU had significantly lower scores on EQ‐5D and in SF‐ 36 all eight dimensions. This was seen both for the general ICU patients as well as for the multiple trauma patients. Significant improvement over time was seen only in single and separate dimensions for the general ICU group, and for the multiple trauma group. Long term effects of ICU care on sleep patterns were found minor as 70 % reported an unchanged sleep pattern and only 9% reported worse sleep after the IC period. Pre‐existing diseases were found to be the factor that had the largest influence on HRQoL in both the short‐ and long term perspective for the general ICU patients as well as for the multiple trauma patients. It was also found to have negative impact on sleep. IC ‐related factors showed only a minor influence on HRQoL or sleep patterns after the ICU stay.

Conclusions: This multicenter study shows that pre‐existing diseases influence the HRQoL short‐ and long‐term after IC, and it must be accounted for when HRQoL and outcome after IC are studied. Approximately, 50% of the decline in HRQoL for the ICU patients could be explained by pre‐existing diseases. Future research needs to focus on the remaining factors of importance for the total HRQoL impairment for these patients.