BACKGROUND:

Several lines of evidence provided the rationale for intervening in children. A large body of autopsy and pathologic evidence had accumulated showing that atherosclerosis, including fatty streaks, increased surface involvement, and advanced microscopic lesions, began in childhood. Blood cholesterol levels tracked from childhood to adulthood, with tracking correlations ranging from .6 to .8. Therefore, a high proportion of children with high levels of cholesterol have high levels as adults. Family clustering of risk factors had also been reported. Studies showed 2-3 times increased prevalence of coronary heart disease in adult relatives of children with high cholesterol compared to children with normal cholesterol, and 2.2 times increased prevalence in high cholesterol in children who had a parent or grandparent with premature coronary heart disease compared with children who did not have a family history of premature heart disease. Finally, there was high likelihood that environmental influences on coronary heart disease risk factors had their behavioral antecents in childhood. Thus, dietary habits which contributed toward elevated blood cholesterol levels were likely to have developed early in life, and it was hoped that behavioral change achieved during childhood was likely to persist into adulthood.

Although numerous studies had shown that dietary modification could lower blood cholesterol levels in adults, only a few studies had shown this effect in children, and none were long-term. Furthermore, the impact on long-term growth and development in children had not been studied. Concerns were raised about the safety of cholesterol-lowering diets in children, particularly during peak growing years. These concerns included possible deficits in growth and nutrient adequacy, and potential adverse psychological effects. This paucity of data was a potential barrier to active prevention measures. To fill this gap in knowledge, the DISC trial, a randomized, controlled clinical trial, tested the efficacy and safety of long-term dietary intervention for reduction of serum LDL-C levels in children during puberty.

DESIGN NARRATIVE:

In the feasibility study, children of both sexes, ages 8 to 10 at baseline starting in 1987, were randomized to either a control group or to a usual care group for whom more intensive dietary intervention for the child and the family was directed. The feasibility study lasted 16 months. The full-scale trial began in December 1988 with the randomization of a total of 663 children. At baseline, mean LDL-C levels, nutrient intakes, anthropometric measurements, nutritional biochemical levels, and psychosocial measures were similar in the two groups. The intervention group was assigned to a series of group and individual sessions to teach the children and their families to follow a diet containing 28 percent of calories as total fat, dietary cholesterol intake less than 75 mg/1000 kcal, and up to 9% of calories from polyunsaturated fat. The diets were designed to meet nutritional requirements of growing children. The usual care group was provided a packet of general dietary information only. The primary efficacy outcome was a difference in changes in LDL-C levels between the two groups at 36 months. Primary safety endpoints were change in height and serum ferritin levels. Secondary safety outcomes included serum zinc, retinol, albumin levels, red blood cell folate, ratio of LDL-C to high-density lipoprotein cholesterol, sexual maturation, cognitive development, and psychosocial assessments. Recruitment was completed in July 1990. Intervention and follow-up was extended until 1997 when the participants were on average 17 years old. Data analysis continued through January 1999.