Syntes: Crowley et al. (2024) — short sleep before or after learning lowers later memory by a small amount

Källa: Crowley, R., Alderman, E., Javadi, A.-H. & Tamminen, J. (2024). A systematic and meta-analytic review of the impact of sleep restriction on memory formation. Neuroscience & Biobehavioral Reviews 167, 105929. https://doi.org/10.1016/j.neubiorev.2024.105929

Verified content

• [full text] 125 effect sizes from 39 reports, 1,234 participants; restricted sleep (3–6.5 h) vs normal sleep (7–11 h). Overall memory impairment g = 0.29 (95% CI 0.13 to 0.44); 0.23 without outliers. No evidence of publication bias.
• [full text] Timing did not significantly moderate the effect (Q = 0.71, p = .40; without outliers p = .69): restriction before encoding g = 0.24 (CI 0.02 to 0.46; k = 43), 0.21 without outliers; after encoding g = 0.36 (CI 0.16 to 0.56; k = 72), 0.25 (CI 0.09 to 0.42) without outliers (Table 2).
• [full text] Number of restriction nights did not moderate the effect (β = −0.02, p = .57). Declarative memory g = 0.30 (CI 0.13 to 0.46; k = 100).
• [full text] Lo, Bennion & Chee 2016's post-encoding prose outcomes are coded in the direction of impairment (g = 0.09 to 0.41), though that study's own tests were not significant (Table 1).

Limits

• [full text] 60% of effect sizes restricted sleep for a single night, and only one for more than 7 nights; nearly all non-declarative effect sizes come from post-encoding studies; English-language reports only, mostly Western samples (section 4.7).
• [assessment] Most tests were within days, not weeks; the pooled after-encoding estimate mixes memory types and mostly single nights.

Why it is in the library

Applied 2026-11-01 (nightly attacks) against C21's second sentence ("short sleep after learning does not clearly increase forgetting"): across studies, restriction after encoding impairs memory about as much as restriction before it.

Added 2026-11-01 by the project. [full text] = read in the published article.