RT Journal Article SR Electronic T1 Age in epidemiological analysis JF Journal of Epidemiology and Community Health JO J Epidemiol Community Health FD BMJ Publishing Group Ltd SP 397 OP 397 DO 10.1136/jech.57.6.397 VO 57 IS 6 A1 S A Reijneveld YR 2003 UL http://jech.bmj.com/content/57/6/397.abstract AB