Sleep Promoting Effects of Lettuce (Lactuca sativa L.) Extracts in Korean Adults with Poor Sleep Quality: A Randomized, Double-Blind Placebo-Controlled Trial

<b>Background/Objectives</b> Lettuce is known to contain compounds that promote sleep. This study aims to evaluate the effects of lettuce extract on Korean adults experiencing poor sleep quality. <b>Methods</b> In this randomized, double-blind, placebo-controlled trial, participants aged 30-65 with poor sleep quality (Pittsburgh Sleep Quality Index (PSQI) > 5) were recruited. Over 4 weeks, participants took two capsules daily of either the test extract or placebo. Sleep quality and quantity were assessed using the PSQI, actigraphy and polysomnography, and analyzed using ANCOVA adjusting for baseline, age, and sex. <b>Results</b> The adjusted final PSQI scores showed greater improvement in the test group than in the placebo group for both the global scores (6.48 ± 0.63 vs. 7.41 ± 0.57, <i>p</i> = 0.0462). Regarding actigraphy measurements, the adjusted final means showed significant improvements in the test group compared to the placebo group for total sleep time (TST) (421.68 ± 13.29 vs. 386.57 ± 12.27 min, <i>p</i> = 0.0023) and sleep efficiency (SE) (83.90 ± 1.6 vs. 81.01 ± 1.50%, <i>p</i> = 0.0342). Polysomnography results also favored the test group, with higher adjusted final means TST (358.90 ± 19.75 vs. 322.11 ± 17.66 min, <i>p</i> = 0.0457) and SE (86.86 ± 3.31 vs. 79.60 ± 2.99%, <i>p</i> = 0.0182), and lower wake after sleep onset (39.26 ± 10.57 vs. 68.15 ± 9.60 min, <i>p</i> = 0.0042). <b>Conclusions</b> Heukharang extract may enhance sleep quality and quantity and is deemed safe, suggesting its potential as a functional food for improving sleep.