October 1, 2012 (Toronto, Ontario) — The relationship between poor sleep and cardiovascular risk seems to start in adolescence, according to the results of a new study [1].
The study, published online in CMAJ on October 1, 2012, found that healthy adolescents who had higher levels of sleep disturbances were also more likely to have cardiovascular risk factors.
Senior author Dr Brian McCrindle (Hospital for Sick Children, Toronto, ON) commented to heartwire : "As this is a cross-sectional study, we can't say the association is causal. We would need a longitudinal study to answer that question. But from the literature it does seem likely that there may be some causality here."
He added: 'The whole field of cardiovascular risk in children and adolescents is not really a high priority, but this needs to change. We know the process of atherosclerosis starts in youth."
Bad Sleep Is a Health Issue
McCrindle recommended that parents and clinicians pay more attention to good sleep practices, as there is mounting evidence that this is a health issue. He suggested several interventions that might improve sleep patterns, including strict bedtimes, lack of media use before bed, and restricting caffeinated beverages. "The bedroom itself should be a place to sleep and not be a place of stimulation, full of televisions, computers, and game consoles."
Noting that this study addressed only cardiovascular risk factors, McCrindle pointed out that there is a whole series of literature on the effects of bad sleep patterns on school performance. "Teenagers get into a vicious circle of not sleeping well and so hype themselves up on caffeinated beverages, which worsens their sleep the next night, etc."
For the study, 4104 individuals 14 to 15 years of age underwent health screening, which included several cardiovascular risk factors and questions on diet. They were also given an extensive sleep questionnaire based on the Pittsburgh Sleep Quality Index.
In total, 19% of participants reported their sleep quality as fairly bad or very bad on weeknights, and 10% reported it as fairly bad or very bad on weekends.
Diet and Exercise Involved
Students who consumed more fried foods, soft drinks, sweets, and caffeinated drinks; exercised less; and had more screen time had higher sleep-disturbance scores.
After correction for other factors, a higher sleep-disturbance score was associated with a higher cholesterol level, higher body-mass index (BMI), larger waist size, higher blood pressure, and increased risk of hypertension.
Odds Ratios for High CV Risk Factors for Adolescents in Top Tertile of Sleep Disturbance Scores (vs Bottom Tertile)
| Risk factor | Odds ratio (95% CI) | p |
| High CV risk* | 1.43 (1.16–1.77) | <0.001 |
| Hypertension | 1.44 (1.02–2.05) | 0.05 |
| Raised non-HDL cholesterol | 1.28 (1.0–1.64) | 0.05 |
*High cardiovascular risk defined as non-HDL cholesterol >3.10 mmol/L; blood pressure >90th percentile, or BMI >85th percentile
Shorter sleep duration was also associated with higher BMI and waist size but not increased cholesterol levels or blood pressure.
McCrindle noted that current recommendations for adolescents advise nine hours sleep per night. Individuals in this study were getting an average of 7.9 hours on weekdays and 9.4 hours on weekends. "But the literature is starting to suggest that the benefits of sleep aren't something that can be caught up at weekends," he added.
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