Oversleeping, late bedtime detrimental in GDM

In pregnant women with gestational diabetes mellitus (GDM), prolonged sleep duration and late bedtime may adversely affect glycaemic control and increase the risk of hypoglycaemia, respectively, according to two studies.

Oversleeping

In the first study, analysis of continuous glucose monitoring (CGM) data showed that sleeping for more than 9 hours per day was associated with significantly impaired glycaemic profiles compared with a shorter sleep duration per day (<9 h/day). These included higher mean glucose levels (p=0.005), increased glucose variability (standard deviation: p<0.001; coefficient of variation: p=0.001; mean amplitude of glycaemic excursions: p=0.001), prolonged time above range (p=0.002), reduced time in range (p=0.003), and elevated glucose risk index (p=0.011). [ATTD-Asia 2025, abstract SOP034]

Functional data analysis indicated that those who were sleeping longer than 9 hours per day had markedly higher daytime glucose levels during a continuous 12.8-hour window, from 10:40 to 23:30, with increases ranging from 2.2 to 5.4 mg/dL.

A total of 282 pregnant women with GDM (mean gestational age 26 weeks) participated in the study. These women wore CGM for 14 days, with sleep data and baseline characteristics collected using a structured questionnaire.

Sleeping late

In the second study, late sleepers (those whose median sleep hour fell at or after 05:00) spent a significantly greater percentage of time below range (p<0.001) compared with early sleepers (those whose median sleep hour fell before 05:00). [Hui Z, et al, ATTD-Asia 2025]

Late sleepers also showed markedly higher low blood glucose index (p=0.002), greater glucose variability (coefficient of variation: p=0.017; mean of daily differences: p=0.005), and elevated glucose risk index (p=0.023).

In functional data analysis, glucose levels in late sleepers were significantly lower (−4.0 to –9.4 mg/dL) during a cumulative 7.3-h window (08:30–14:20; 19:50–21:20).

The analysis included 373 pregnant women with GDM (mean gestational age 26 weeks, 5.2 percent late sleepers) who completed sleep assessments via structured questionnaires and 14-day CGM. Sleep timing was defined as “early” or “late” based on a 5-AM midpoint.

Individualized interventions

The two studies applied functional data analyses that identified windows where sleep duration and sleep timing significantly influenced glucose variation, the authors noted.

Overall, the findings highlight the value of dynamic, individualized approaches to optimize glucose management in pregnancies complicated by GDM, they added.