TABLE 4.

Heritability estimates for BMI-z_5to10 and the residual phenotypes¹

	MZ and DZ twins	MZ and same-sex DZ twins	MZ twins and DZ twins and siblings2
BMI-z5to10	0.44 (0.04–0.94)	0.67 (0.09–1.43)	0.99 (0.61–1.40)
BMI-z5to103	0.48 (0.04–1.06)	0.97 (0.20–1.86)	1 (0.60–1.44)
BMI-zadj	0.47 (0.06–0.98)	0.82 (0.19–1.61)	1 (0.68–1.50)
BMI-zadjFEV	0.38 (−0.01–0.83)	0.54 (0.04–1.17)	1 (0.76–1.62)

¹All values are means; 95% CIs in parentheses. Confidence intervals on heritability were estimated by using a bootstrapping technique (33). BMI-z_adj, average BMI z score from 5 to 10 y of age adjusted for female sex, birth cohort, pancreatic insufficiency, and history of meconium ileus; BMI-z_adjFEV, average BMI z score from 5 to 10 y of age adjusted as for BMI-z_adj plus for FEVq_6to10; BMI-z_5to10, average BMI z score from 5 to 10 y of age; DZ, dizygous; MZ, monozygous.

²Same-sex DZ twins and siblings with <3 y of difference in age.

³After exclusion of pairs in whom one or both members of the pair had an average height z score from 5 to 10 y of age less than −1.96.