Date Published: July 24, 2017
Publisher: Public Library of Science
Author(s): Chih-Cheng Lai, Chung-Han Ho, Chin-Ming Chen, Shyh-Ren Chiang, Chien-Ming Chao, Wei-Lun Liu, Yu-Chieh Lin, Jhi-Joung Wang, Kuo-Chen Cheng, Yu Ru Kou.
This retrospective, population-based cohort study aims to investigate the long-term risk of newly diagnosed dementia in patients discharged for acute respiratory failure that required mechanical ventilation (MV) and intensive care unit (ICU) admission. From the Taiwan National Health Insurance Research Database, first-time ICU patients using MV between June 1, 1998, and December 31, 2012, were enrolled, and they were followed-up until the earliest onset of one of our two endpoints: a new diagnosis of dementia (primary endpoint), or the end of the study. A total of 18,033 patients were enrolled and thirteen hundred eighty-seven patients had been newly diagnosed with dementia (mean onset: 3.2 years post-discharge). Patients ≥ 85 years old had the highest risk (multivariate analysis). Males had a lower risk than did females in both models (HR: 0.81, 95% CI: 0.72–0.9 in model 1; HR: 0.80, 95% CI: 0.72–0.89 in model 2). ICU stays > 5 days, hospital stays > 14 days, and more ICU readmissions were associated with a higher risk of developing dementia. In conclusion, the long-term risks of a subsequent diagnosis of dementia for acute respiratory failure with MV patients who survive to discharge increase with age and are higher in women than in men. Additionally, the longer the ICU or hospital stay is, and the more ICU readmissions a patient has, are both significantly associated with developing dementia.
Because of the increasing incidence of critical illnesses that require admission to the intensive care unit (ICU) and to the decreasing mortality rates of critically ill patients [1–3], the number of survivors of critical illness is rapidly rising. Although these survivors can recover from their acute illness, they can develop several long-term sequelae, e.g., deterioration of physical functions, post-traumatic stress disorder, depression, and cognitive impairments [4–7]. Several investigations [5, 8–13] have reported significant associations between the development of cognitive impairments, including dementia, and ICU admission, especially in elderly (≥ 65 years old) patients. However, the characteristics of ICU patients are heterogeneous and complex. In addition to the association between age, genetic factors, stroke, dyslipidemima, hypertension, diabetes mellitus, cardiovascular factors, smoking, kidney dysfunction, sepsis, and dementia were ever reported in general population and some critical ill patients [8,9,14–18], and we wondered whether this close relationship between dementia and admission to the ICU could be applied to all ICU patients.
During the study period, 18,033 patients were enrolled (mean follow-up: 8.1 years) (Table 1, Fig 2). There were 1387 patients with newly diagnosed dementia. The overall incidence of dementia was 9.83 per 1000 patient-years (1387 events for 141,121 person-years), and the mean onset of dementia was 3.2 years from ICU admission and MV (overall), and 1.8 years within the first five years of follow-up. Patients who subsequently developed dementia were more likely to be older, female, have had a longer hospital stay, have been readmitted to the ICU, have had more strokes, hypertension, arrhythmia, anxiety, depression, Parkinson’s disease, head injury, or epilepsy than were patients without dementia.
This is the first study that investigates (1) the long term risk of dementia in patients admitted to the ICU and put on MV, and (2) the effects of MV on the risk of dementia of specific groups of critically ill patients. Our most important finding is that of 18,033 patients admitted to the ICU and put on MV, those who survived to hospital discharge for at least 6 months, dementia was newly diagnosed in 1387 (141,121 person-years), and the overall incidence was 9.83 per 1000 person-years over the 8 years of follow-up. The mean onset of dementia was 3.2 years from ICU admission and MV. Guerra et al.  reported that the rate of newly diagnosed dementia in 10,348 patients admitted to the ICU was 15.0% (1648 patients), and the incidence was 73.6 per 1000 person-years over a 3-year follow-up (based on a random 2.5% sample of Medicare beneficiaries who received ICU care and survived to hospital discharge). In contrast to Guerra et al.  enrolled patients ≥ 66 years old, we enrolled patients ≥ 50 years old, and patients 50–64 years old comprised 35% of our study population. In addition, we enrolled only patients admitted to the ICU and put on MV, and all of our patients were Taiwanese. These differences might partially explain why our findings are different from other studies [4, 8, 9, 11] that enrolled primarily Caucasian patients admitted to the ICU but not put on MV. The present study specifically focused on Taiwanese patients admitted to the ICU and put on MV who survived to hospital discharge and then underwent a long-term follow-up.