Researchers observed an “unexpected association” between longer sleep duration in early childhood and lower HDL cholesterol levels in later childhood, whereas the more comprehensive cardiometabolic risk score was not affected by sleep duration, according to findings published in Childhood Obesity.
“Secondary analyses of the individual [cardiometabolic risk] components and BMI z score yielded one association: Later childhood HDL was significantly associated with early childhood sleep duration; however, the relationship was in the unexpected direction,” Catherine S. Birken, MD, MSc, FRCPC, of the department of pediatrics at The Hospital for Sick Children in Toronto, and colleagues wrote. “This relationship remained significant in multivariable models after adjusting for maternal ethnicity, parental BMI, median income from postal code, child’s sex, birth weight, age difference between exposure and outcome, early childhood BMI z score, juice and [sugar-sweetened beverage] consumption, outdoor free play, bottle use in bed, time of blood collection and fasting hours.
In a prospective study, Birken and colleagues analyzed data from 597 healthy children participating in TARGet Kids!, a primary care practice-based research network in Canada. Children aged 0 to 6 years were recruited between December 2008 and February 2016, and followed at scheduled well visits at age 6 months or younger, 6 to 12 months and 18 months, and then annually from age 2 years (mean baseline age, 28 months; mean follow-up age, 55 months). Primary exposure was 24-hour sleep duration measured from age 1 to 3 years; parents completed a questionnaire that asked, “How many hours does your child usually spend sleeping in a 24-hour period?” Researchers used continuous cardiometabolic risk “cluster scores” combining components of adult metabolic syndrome to assess the risk level in the cohort; scores were quantified as the sum of z scores of waist circumference, systolic blood pressure, glucose, triglycerides and inverse HDL cholesterol. A lower cluster score indicates lower cardiometabolic risk. Secondary outcomes included examining sleep duration and individual cardiometabolic risk components and BMI z score. Researchers used linear regression analysis to assess the association between early childhood sleep duration and cardiometabolic risk in later childhood.
The average 24-hour sleep duration in early childhood was 11.8 hours, with 87% meeting or exceeding total sleep recommendations for their age, the researchers wrote. They found that 13% of children were below the recommended sleep range for age; 5% were above the recommended sleep range. Children meeting or exceeding the recommended sleep range tended to be older (P = .04), have less nighttime bottle use (P = .002) and to be born to European mothers vs. children below the recommended range. From age 12 to 36 months, 17% of children were overweight; 4% had obesity.
At follow-up, mean cardiometabolic risk cluster score was –0.22, ranging from –7.05 to 9.06; overall, researchers did not observe any association between early childhood sleep duration and the cardiometabolic risk cluster score in later childhood. However, shorter sleep duration was associated with higher HDL concentrations (adjusted beta = –0.028; 95% CI, –0.049 to –0.007). Results persisted after using age- and sex-standardized components of the cardiometabolic risk cluster score; all other components remained nonsignificant.
“Our findings suggest that sleep duration between 1 and 3 years of age is not associated with a [cardiometabolic risk] score [approximately] 2 years later; however, there may be a relationship with [cardiometabolic risk] in older childhood not captured in our analysis,” the researchers wrote. “Furthermore, sleep quality may be more important than sleep duration on cardiometabolic disease risk in young children. Further research is needed to confirm these findings in addition to the unexpected association between longer sleep duration and decreased HDL concentrations.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.