Sleep Extension Improves Alertness And Performance During And Following Subsequent Sleep Restriction

The study, authored by Tracy L. Rupp, PhD, of the Walter Reed Army Institute of Research, focused on 11 males and 13 females, who were randomly assigned to either an Extended (10 hours time in bed) or Habitual sleep group for one week followed by one baseline, seven sleep restriction (three hours time in bed), and five recovery nights (eight hours time in bed). Throughout baseline, restriction and recovery, volunteers were administered the Psychomotor Vigilance Task (PVT), Maintenance of Wakefulness Test (MWT), and Stanford Sleepiness Scale (SSS).

According to the results, sleep latency was longer for the Extended group on day one. During restriction, PVT performance and alertness declined in both groups, but declines were faster for the Habitual group. During recovery, Extended group PVT performance was restored to baseline after the first recovery night, although alertness scores remained low. For the Habitual group, PVT performance failed to recover, although SSS and MWT scores were restored to baseline after one to two nights of recovery sleep.

"The present study reveals that protective effects accrue from extending the duration of nightly sleep," said Dr. Rupp. "Specifically, the deficits in performance and alertness that result from subsequent sleep loss are minimized -- and the speed with which recovery from sleep loss is enhanced -- when 'extra' sleep has previously been obtained. These findings suggest that individual differences in resilience to sleep loss are at least partly a function of modifiable long-term sleep habits, rather than being an unmodifiable, trait-like characteristic of individuals. From a practical standpoint, this suggests that the benefits of sleep can effectively be 'banked' and later 'withdrawn' as needed to optimize alertness and performance during subsequent periods of sleep loss."

It is recommended that adults get between seven and eight hours of nightly sleep.