0171 Meal Inertia: The Impact of Eating Different Sized Meals on Vigilant Attention Throughout the Night

Abstract

Introduction: Shiftworkers eat during the night when sleep propensity is greatest and the body is not primed to digest food. It is unknown if attention is affected immediately after eating at night and whether, like sleep inertia, this effect is transient and dose‐dependent. This study investigated whether a meal, a snack or not eating, differentially impacted attention throughout the nightshift. Methods: Healthy males (n=19) and females (n=11) aged 18‐39 years (BMI 23.4 ± 2.3kg/m2) underwent four simulated nightshifts. Participants were randomly allocated to one of three conditions: meal (n=10; males:females, 5:5) or snack (n=10; 6:4), with 30% and 10% of 24h energy intake respectively consumed at 0030h, or no eating (n=10; 8:2), with no energy consumed during the night. Across conditions, total macronutrient intake and individual energy needs were maintained and constant each 24h. Participants completed a 3‐minute Psychomotor Vigilance Task immediately pre‐mealtime at 0030h and then 0, 30, 60, 120, 210 and 270 minutes post‐mealtime. Results: Mixed model analyses were conducted for the variables, reciprocal of the mean response time (mean RRT) and mean number of lapses (lapses defined as RT>;355ms). There was a significant interaction between condition and performance time for mean RRT (p=0.02) and mean lapses (p<0.001), such that attention was impaired immediately after the meal compared to the snack (mean RRT mean±SE: 4.4 ± 0.1 vs 4.6 ± 0.1 1/ms; mean lapses: 4.2 ± 0.9 vs 2.3 ± 0.8). This impairment lasted throughout the nightshift, with significant impairment after the meal compared to the snack 270 mins post‐mealtime SLEEP, Volume 41, Abstract Supplement, 2018 A68 (mean RRT: 3.5 ± 0.6 vs 5.2 ± 0.6 1/ms; mean lapses: 3.5 ± 0.1 vs 4.3 ± 0.1). No differences were found between the snack and no eating conditions. Conclusion: These results indicate an effect of 'meal inertia', whereby attention is impaired immediately after eating a meal, but not a snack, and this impairment lasts throughout the night. Reducing the size of the meal eaten during the shift may reduce performance impairments, and this has implications for those who eat at night and then immediately return to work.