Time of day affects episodic memory in older adults.

The neuropsychological test scores of 2030 cognitively normal older adults were examined to evaluate performance patterns as they related to time of day (TOD) at which testing was initiated. Multiple regression analyses were used to examine the association of TOD with scores on seven neuropsychological tests used in the clinical evaluation of dementia. Episodic memory performance was significantly related to TOD, while memory span and verbal fluency were not. Best performance occurred during early morning hours and late afternoon; worst performance occurred mid-day (i.e., noon). These findings may have implications for clinical assessment, the design of research on dementia, and the daily functioning of older adults.