Multiple sleep latency tests during the constant routine.
Level 3 - non-randomized controlled study
Non-randomized laboratory physiological study comparing three distinct age cohorts under a constant routine protocol.
PubMed 1455121 · doi:10.1093/sleep/15.5.396
What was done
Researchers assessed whether the afternoon "post-lunch dip" in alertness reflects an endogenous sleep tendency rhythm rather than food intake. Sleep tendency was measured using the Multiple Sleep Latency Test (MSLT) at 2-hour intervals in 16 volunteers across three age groups (ages 10–12, 16–17, and 62–74 years). Testing took place during a constant routine protocol during which small meals were administered every hour to eliminate postprandial confounding.
What was found
The abstract reports directional and significance findings without numerical latency values: - Baseline scores showed no statistically significant Time of Day effect, though a trend for an afternoon dip was present in the eldest group. - During the constant routine, a statistically significant Time of Day effect was observed for the two older groups (adolescents and older adults), showing an increased midday sleep tendency. - No significant Time of Day effect was found for the prepubertal group (ages 10–12).
Why it matters
These results provide evidence that the midday dip in alertness is regulated by an endogenous circadian or maturational process rather than digestive somnolence from a large meal.
Limits
The overall sample size is very small (n = 16 divided across three age cohorts, averaging roughly 5 participants per group). The abstract omits numerical sleep latencies, effect sizes, and variance metrics. Key age groups (such as young and middle-aged adults) were not assessed.
Cited by
- context Humans are biologically crepuscular, experiencing higher alertness in the morning and evening and a physiological increase in sleep pressure after lunch.