Dietary counseling for patients with cardiovascular disease (CVD) improved diet quality over six months, but this did not translate into better sleep outcomes, according to a secondary analysis of a randomized controlled trial published in the Journal of Sleep Research.
The Study
Verkaar and colleagues conducted a secondary analysis of a six-month, two-arm, parallel randomized controlled trial (registered at clinicaltrials.gov, NCT05071092) among patients with established CVD recruited from two Dutch hospitals. The parent trial originally assessed the effects of dietary counseling on cardiovascular risk profiles (van Damme et al., Clinical Nutrition, 2025).
A total of 112 patients (mean age 68.9 years, 74% male, mean BMI 27.7 kg/m²) were included. Participants were randomly assigned 1:1 to receive dietary counseling (n=57) or usual care (n=55), stratified by hospital site. The study was not blinded.
Intervention and Outcomes
The intervention group received up to five hours of dietary counseling across seven sessions over six months, delivered by a dietitian. Counseling targeted the Dutch dietary guidelines: increasing vegetables, fruit, whole grains, legumes, nuts, dairy, fish, and tea, while reducing salt, red and processed meat, sugary drinks, and alcohol. The control group received usual care. No sleep-specific advice was provided to either group.
Diet quality was assessed using a food frequency questionnaire yielding a Dutch Healthy Diet Index score (range 0 to 160, higher scores indicate better adherence). Sleep outcomes were measured with the Pittsburgh Sleep Quality Index (PSQI) at baseline and six months. A PSQI score above 5 indicated poor sleep quality.
Key Findings
At baseline, 32% of participants had poor sleep quality (median PSQI 5.0, IQR 3.0 to 8.0). Most (87%) used no sleep medication.
Diet quality improved more in the intervention group (from 104.7 to 117.0) than in the control group (from 102.1 to 107.7). The adjusted mean difference was 7.7 points (95% CI 1.2 to 14.2), confirming successful dietary improvement.
However, this improvement did not produce corresponding sleep benefits. The intervention did not result in statistically significant changes in any sleep outcome. For overall PSQI score, the adjusted mean difference was 0.2 points (95% CI -0.6 to 1.0). Sleep duration changed by 9.0 minutes (95% CI -15.8 to 33.8), sleep onset latency by 3.8 minutes (95% CI -3.5 to 11.1), and sleep efficiency by -0.2 percentage points (95% CI -4.0 to 3.7). All confidence intervals crossed zero.
Sensitivity Analyses
Sensitivity analyses reinforced the primary finding. When restricted to participants with poor sleep at baseline, the PSQI difference was 0.1 points (95% CI -1.8 to 1.9). Per-protocol analyses limited to those who attended at least five sessions, or who improved diet quality by at least half a standard deviation, similarly showed no benefit.
Interpretation
The authors suggest two possible explanations. First, the improvements in diet quality, while statistically significant, may have been too modest to affect sleep physiology. Second, improving diet quality may simply not meaningfully affect sleep among patients with established CVD, at least over six months.
These results are notable because sleep problems affect roughly one in three CVD patients, and dietary interventions are frequently proposed as an accessible, low-risk strategy for improving sleep. This trial suggests that dietary counseling alone, without a sleep-specific component, is unlikely to improve sleep outcomes in this population, even when it successfully improves dietary adherence.
Strengths and Limitations
Strengths include the randomized design and validated instruments for diet and sleep. Limitations include the modest sample size, lack of blinding, reliance on self-reported sleep (rather than actigraphy or polysomnography), and the relatively short six-month follow-up. The cohort was predominantly older, male, and Dutch, which may limit generalizability.
Bottom Line
Six months of dietary counseling in patients with CVD improved diet quality but did not improve sleep quality, sleep duration, sleep onset latency, or sleep efficiency as measured by the PSQI. These findings suggest that improving diet alone, without targeted sleep interventions, may be insufficient to address sleep problems in this population.