Table 1.

Design heterogeneity in studies on the effects of natural light exposure on patients in the intensive care unit

Author (reference)	Design (N)	Sample size calculation	Delirium definition	Screening tool	Screen frequency (no./day)	ICU patient population	Delirium incidence or severity with NL exposure
Our study	Retrospective analysis of prospective study (181)	Yesa	DSM-IV-TR	CAM-ICU	3	Long stay medical and surgical with ARDS	Decreased
Arenson [6]	Retrospective (1010)	No	Not reported	CAM-ICU	3	Post-operative	No change
Estrup [5]	Retrospective (183)	No	Not reported	CAM-ICUb	2	Unspecified	No change
Kohn [7]	Retrospective (6631)	No	Not reported	Nonec	1	Medical ICU patients	No change
Smonig [1]	Prospective, observational (195)	Yesa	Not reported	ICDSCc	2	On MV of any etiology/duration	No changed
Zaal [8]	Prospective, before–after (130)	No	Not reported	CAM-ICU	1	Medical and surgical	No change

ARDS acute respiratory distress syndrome, CAM-ICU confusion assessment method for the ICU, DSM Diagnostic and Statistical Manual of Mental Disorders, ICDSC Intensive Care Delirium Screening Checklist, MV mechanical ventilation

^aTo achieve a power of power 80% to detect a decrease of delirium from 80 to 60% (two-sided test, alpha = 0.05), the necessary sample size is 180 patients [1] would be necessary

^bDelirium categorization included any patient treated with haloperidol, regardless of CAM-ICU screen

^cRequired a positive screen for at least 2 consecutive days to be considered positive

^dLess haloperidol administration; less hallucinations