Table 4.  Characteristics of children in the original trial of types of infant formula who were enrolled into the follow up study, compared with reference group of breastfed children. Figures are means (SD) except where otherwise indicated Characteristics Formula fed children (n=147) Breast fed children (n=88) P value Age of mother (years) at follow up 34.4 (5.6) 35.9 (4.1) 0.031 Age of mother (years) at completion of education 18.2 (3.1) 18.9 (3.6) 0.111 Age of father (years) at follow up 36.0 (5.3) 39.2 (5.1)  0.0001 Age of father (years) at completion of education 17.8 (2.8) 19.5 (4.8) 0.003 No of mothers married or with partner/No of single mothers* 130/14 78/5 0.239 No of children in home  2.1 (1.0)  2.5 (1.2) 0.01 No of smokers in household  0.78 (0.75)  0.35 (0.60)  0.0001