Adverse interaction effects of chronic and acute sleep deficits on spatial working memory but not on verbal working memory or declarative memory.

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The accumulation of chronic sleep deficits combined with acute sleep loss is common in shift workers and increases the risk of errors and accidents. We investigated single and combined effects of chronic and acute sleep loss and recovery sleep on working memory performance (N-back task) and on overnight declarative memory recall (paired-associate lists) in 36 healthy participants. After baseline measurements, the chronic sleep restriction group (n=21; mean [SD] age 26[4]years) underwent 5nights of sleep restriction (5-hr time in bed [TIB]), whereas the control group (n=15; mean [SD] age 28[6]years) had 8-hr TIB during those nights. Afterwards, both groups spent 1night with 8-hr TIB prior to acute sleep deprivation for 38hr, and a final recovery night (10-hr TIB). Chronic sleep restriction decreased spatial N-back performance compared to baseline (omissions: p = .001; sensitivity: p = .012), but not letter N-back performance or word-pair recall. Acute sleep deprivation impaired spatial N-back performance more in the chronic sleep restriction group than in the control group (interaction between group and time awake: p ≤ .02). No group differences during acute sleep loss appeared in letter N-back performance or word recall. It is concluded that chronic sleep loss, even when followed by a night of recovery sleep, increases the vulnerability to impairments in spatial working memory during subsequent acute sleep loss. Verbal working memory and declarative memory were not affected by restricted sleep.