As the first and only manifestation of ischemic heart disease, sudden unexpected cardiac death (SUCD) is a serious clinical and epidemiological concern. Prospective population studies permit the identification of risk factors for SUCD. Knowledge of the short-and long-term risks for SUCD are key to understanding the basis of any intervention. The present paper explores the effect of time since the detection of factors on the risk for SUCD. The Manitoba Follow-Up Study is a longitudinal, prospective study of 3983 originally healthy young men who have been followed with routine medical examinations since 1948. During 56 years of follow-up, SUCD occurred in 171 men. This analysis examined 21 possible risk factors for SUCD, including clinical findings, social variables and electrocardiographic abnormalities. Time-dependent covariate Cox proportional hazard models were used to estimate age-adjusted relative risks for SUCD. In multivariate models, the relative risk of SUCD was estimated as a function of time since the documentation of each risk factor. Excess alcohol consumption and T wave changes were associated with a high short-term risk for SUCD. Arterial hypertension and ST/T changes had sustained excess risk over both the short and long term. Newly developed left bundle branch block was a highly significant short-term risk that diminished with time. These findings add new information for the clinical management of risk factors. The identification of time since the detection of these risk factors is an important consideration to reduce SUCD.