Note that more than 90% of records had valid data for the smoking status at initial assessment data item, across all health boards, in all years.
Roedd data dilys i’w gael ar gyfer mwy na 90% o’r cofnodion mewn perthynas â statws smygu yn yr asesiad cychwynnol, a hynny ar draws yr holl fyrddau iechyd ac ym mhob blwyddyn.