Glucose control upon waking is unaffected by hourly sleep fragmentation during the night, but is impaired by morning caffeinated coffee

Abstract

Morning coffee is a common remedy following disrupted sleep yet each factor can independently impair glucose tolerance and insulin sensitivity in healthy adults. Remarkably, the combined effects of sleep fragmentation and coffee on glucose control upon waking per se have never been investigated. In a randomised cross-over design, 29 adults (Mean ± SD; age: 21 ± 1 years, BMI: 24.4 ± 3.3 kg·m-2) underwent three oral glucose tolerance tests (OGTT). One following a habitual night of sleep (Control; in bed, lights-off trying to sleep ~2300-0700 h) the others following a night of sleep fragmentation (as Control but waking hourly for 5 min), once with and once without morning coffee ~1 h after waking (~300 mg caffeine as black coffee 30 min prior to OGTT). Peak plasma glucose and insulin concentrations were unaffected by sleep quality but were higher following coffee consumption (Mean [normalised confidence interval] for Control, Fragmented, and Fragmented+Coffee, respectively; Glucose: 8.20 [7.93-8.47] mmol∙L-1versus 8.23 [7.96-8.50] mmol∙L-1versus 8.96 [8.70-9.22] mmol.L-1; Insulin: 265 [247-283] pmol∙L-1; and 235 [218-253] pmol∙L-1; and 310 [284-337] pmol∙L-1). Likewise, iAUC for plasma glucose was higher in the Fragmented+Coffee trial compared to Fragmented. Whilst sleep fragmentation did not alter glycaemic or insulinaemic responses to morning glucose ingestion, if a strong caffeinated coffee is consumed then a reduction in glucose tolerance can be expected.

Nutrient timing and metabolic regulation

“…Interestingly, based on the reasoning that a strong coffee is a common remedy following a night of broken sleep, we also investigated the effects of caffeine within the context of the above experimental model. Consistent with the established effects of caffeine on insulin sensitivity independent of sleep deprivation (Robertson et al 2015;Robertson et al 2018), consuming a cup of coffee following a night of sleep fragmentation resulted in a ∼50% higher glycaemic response and ∼15% higher insulinaemic response at breakfast than either a night of uninterrupted sleep or a matched sleep fragmentation protocol without caffeine prior to breakfast (Smith et al 2020). Further work is therefore needed to better understand whether the potential opportunity for nutritional intervention at night can be harnessed with minimal disruption of sleep patterns, circadian rhythms and next-day metabolic responses.…”

“…The latter refers to when sleep is intermittently disrupted by brief waking periods and has the potential to interrupt progression through the various stages of the sleep cycle even if total sleep duration is not substantially curtailed (Tasali et al 2008). We tested the effect of fragmented sleep in our recent work but found post-prandial glucose and insulin responses upon waking to be unaffected by having woken hourly throughout the prior 8-h sleep opportunity (Smith et al 2020). Interestingly, based on the reasoning that a strong coffee is a common remedy following a night of broken sleep, we also investigated the effects of caffeine within the context of the above experimental model.…”

“…We tested the effect of fragmented sleep in our recent work but found post‐prandial glucose and insulin responses upon waking to be unaffected by having woken hourly throughout the prior 8‐h sleep opportunity (Smith et al . 2020 ). Interestingly, based on the reasoning that a strong coffee is a common remedy following a night of broken sleep, we also investigated the effects of caffeine within the context of the above experimental model.…”

Changes in Insulin Sensitivity and Lipid Profile Markers Following Initial and Secondary Bouts of Multiple Eccentric Exercises

“…Plasma CK activity was analyzed spectrophotometrically by an automated clinical chemistry analyzer (Model 7080; Hitachi, Co. Ltd., Tokyo, Japan) using a commercially available test kit (e.g., Chou et al, 2018 ; Chen et al, 2019a , Chen et al, 2019b ; Kang et al, 2022 ). Serum glucose concentration was assayed by a Beckman Unicel DxC 600/800 Chemistry Analyzer (Beckman Coulter Inc., Fullerton, CA, United States of America) using a commercially available kit (GLUCm) (e.g., Smith et al, 2020 ; Tsai et al, 2021 ). Serum insulin concentration was analyzed by an immunoradiometric assay kit (INS-IRMA kit; Biosource, Nivelles, Belgium) using a gamma counter system (MIC Group, Inc., Ramsey, MN, United States of America) (e.g., Chen et al, 2017a ; Lee et al, 2018 ).…”

Changes in plasma C1q, apelin and adropin concentrations in older adults after descending and ascending stair walking intervention

“…For the OGTT, capillary blood samples were obtained from the fingertips of each participant using sterilised Softclix lancets (Roche Diabetes Care Ltd., Surrey England, UK) before and 30, 60, 90 and 120 min after consumption of a 75-g standard glucose drink, and blood glucose concentrations were measured with an analyser (Johnson & Johnson, Livingstone, Scotland, UK). The detailed procedures used for analyses of glucose, insulin, OGTT, HbA1c, HOMA, TG, TC, LDLC, and HDLC were described previously 7 , 63 – 65 .…”