Lower respiratory tract infection ( LRTI ) by 1 year ( relative risk [ RR ] , 3.00 ; 95 % CI , 1.58-5 .70 ) , childcare by 1 year ( RR , 1.51 ; 95 % CI , 1.02-2 .22 ) , and higher body mass index ( RR , 2.51 ; 95 % CI , 1.09-5 .81 ) were associated with increased risk of early transient wheeze , whereas breastfeeding was protective ( RR , 0.54 ; 95 % CI , 0.32-0 .90 ) .