Light exposure during sleep impairs cardiometabolic function

Figures

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  Fig. 1.. Schematic of laboratory protocol. OGTT: oral glucose tolerance test.

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  Fig. 2.. HOMA-IR for room light (n = 10) and dim light (n = 10) conditions on Day 1 and Day 2. HOMA-IR was significantly higher on Day 2 compared to Day 1 in the room light condition versus the dim light condition. P values refer to the change from Day 1 to Day 2 between conditions (unpaired Student’s t test). The error bars represent SD.

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  Fig. 3.. Glucose and insulin measures from 2-h OGTT for room light (n = 10) and dim light conditions (n = 10) on Day 1 and Day 2. Within group changes in glucose levels (A and B) on Days 1 and 2 were similar between room light and dim light conditions while within group changes in insulin levels (C and D) were significantly higher on Day 2 after sleeping in room lighting in the room light condition compared to the dim light condition (General Linear Model: condition × day P = 0.034). Higher insulin levels on Day 2 in the room light condition were most pronounced at 20 and 30 min post ingestion of the glucose bolus. *P < 0.05. The error bars represent SD.

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  Fig. 4.. Early phase insulin response (30-min AUC) during the OGTT for room light (n = 10) and dim light (n = 10) conditions on Day 1 and Day 2. Insulin 30-min AUC and HOMA-IR were significantly higher on Day 2 compared to Day 1 in the room light condition versus the dim light condition. P values refer to the change from Day 1 to Day 2 between conditions (unpaired Student’s t test). The error bars represent SD.

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  Fig. 5.. Matsuda insulin sensitivity index for room light (n = 10) and dim light (n = 10) conditions on Day 1 and Day 2. Matsuda index (y-axis) was calculated as 10,000/square root of [fasting glucose × fasting insulin] × [mean glucose × mean insulin during OGTT]. Matsuda index was significantly lower on Day 2 compared to Day 1 in the room light condition versus the dim light condition. P values refer to the change from Day 1 to Day 2 between conditions (unpaired Student’s t test). The error bars represent SD.

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  Fig. 6.. (Top, A and B): HR during the sleep period for room light (n = 10) and dim light (n = 10) conditions on Night 1 and Night 2. (Lower, C and D): LF/HF derived from HRV analysis during the sleep period for room light (n = 10) and dim light (n = 10) conditions on Night 1 and Night 2. Beat-to-beat HR during the sleep period was averaged every 10 min across the sleep period, starting from the time at lights off. Change in HR from Night 1 to Night 2 was significantly larger in participants randomized to the room light condition (A) compared to those randomized to the dim light condition (B) (General Linear Model: condition × night P < 0.001). LF/HF was calculated on time windows with a stable signal of at least 5 min for the entire duration of the sleep period, starting from lights off. Change in LF/HF from Night 1 to Night 2 was significantly larger in participants randomized to the room light condition (C) compared to those randomized to the dim light condition (D) (General Linear Model: condition × night P < 0.019). The error bars represent SD.

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  Fig. 7.. Pairwise correlations between the change in LF/HF obtained from HRV and averaged across the sleep period (Night 1 to Night 2) and the change in the AUC of insulin at 30 min from OGTT (Day 1 to Day 2). A significant positive correlation between LF/HF change and the change in the AUC of insulin at 30 min was observed in participants randomized to the room light condition (A, n = 10), and not in those randomized to the dim light condition (B, n = 10). The dotted lines represent 95% CIs.