- Design
- Systematic review and meta-analysis of randomised trials
- Population
- 10 RCTs, 2,827 people with diabetes
- Primary outcome
- Sleep quality and HbA1c
- Effect
- HbA1c MD −0.35% (95% CI −0.44 to −0.25), I² 94%; sleep quality MD −1.47 (−1.98 to −0.96)
A meta-analysis pooled ten randomised trials (2,827 participants from four countries) comparing cognitive behavioural therapy for sleep with usual care or health education in people with diabetes.
CBT improved sleep quality (mean difference −1.47 on sleep scales, 95% CI −1.98 to −0.96) and was associated with HbA1c 0.35 percentage points lower (95% CI −0.44 to −0.25). Insomnia severity also improved. BMI did not change. Heterogeneity was very high for every outcome except BMI (I² 88–94%).
The direction is consistent with what is known about short sleep and insulin resistance, and the intervention carries little harm. Asking about sleep is cheap; referral for CBT for insomnia, or a structured digital programme, is a reasonable addition for patients with poor sleep and persistent hyperglycaemia. It does not replace medication changes.
- Ask about sleep at diabetes reviews, especially when HbA1c is stuck despite treatment.
- Offer CBT for insomnia rather than hypnotics where poor sleep is the problem.
- Screen for obstructive sleep apnoea before attributing poor sleep to insomnia.
- Use sleep therapy alongside, not instead of, glucose-lowering treatment.
Why it matters
Sleep is rarely asked about in diabetes clinics, yet treating it was associated with an HbA1c change comparable to some add-on drugs.
Don't overread it
With I² above 85%, the trials disagreed widely — the pooled HbA1c effect is an average of very different results.
The statistics, in plain English
I² measures how much the trials disagree beyond chance; values above 75% are considered high, so the single pooled number hides a wide range. The HbA1c interval of −0.44 to −0.25 does not cross zero, so the average effect is unlikely to be chance, but individual results will vary.
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