August 7th, 2012
Survey Finds Significant Drop in Cholesterol Levels in Youths
New data from the National Health and Nutrition Examination Survey (NHANES), published in JAMA, show significant and perhaps surprising improvements over the last 20 years in the lipid profile of youths aged 6-19 years. Among the key lipid parameters measured by the survey from 1988-1994 to 2007-2010:
- Total cholesterol decreased from 165 mg/dL to 160 mg/dL (p<0.001)
- Prevalence of elevated total cholesterol declined from 11.3% to 8.1% (p<0.002)
- HDL increased from 50.5 mg/dL to 52.2 mg/dL (p<0.001)
- Non-HDL decreased from 115 mg/dL to 107 mg/dL (p<0.001)
“Generally,” the authors report, “the sex-, age-, and race/ethnicity-specific trends for TC, HDL-C, and non– HDL-C were similar in direction to the overall trends and consistent with a favorable trend, although for each group, the magnitude was not the same and the trend was not always significant.”
The change over time in lipids in youths was paralleled by similar changes in adults, according to the investigators. They also note that the improvement in lipids occurred “despite an increase in obesity prevalence during the study period.”
The changes recorded in the survey are “clinically meaningful” and a “cause for optimism,” writes Sarah de Ferranti in an accompanying editorial. “But,” she asks, in the face of the increase in obesity, the decline in exercise, and other adverse trends, “why would childhood cholesterol improve?” She briefly considers several possible explanations for the improvement, including improved interventions and healthier lifestyles, but then finds “a more plausible explanation” to be “dietary shifts at a population level”:
Dietary intake of fat has declined over the past several decades and some studies suggest substitution of carbohydrates for dietary fat, particularly poor quality carbohydrates, might both promote obesity and explain some of the lipid changes reported [here].
Another less concerning cause may be the reduction in the use of trans fats over the study period, she writes.