MeasuresofAssociationratestandardization.pptVIP

Measures of Association rate standardization 白其卉 中研院生醫所 For lecture 2002/12/02 Association Index: measures of association -- Index of measured relationship of risk factor (RF) and disease (Dx) 表示危險因子與疾病間的相關程度之指標 Introduction Analytic epidemiology (epi) Cohort study (prospective) Fixed cohort Dynamic cohort Case-control study (retrospective) Major aims in analytic epi verify the relationship of RF Dx How do we describe risk its association on risk? Measures of Association Absolute risk Attribute risk Relative risk Risk ratios (RR) Odds ratios (OR) Risk Difference Absolute risk Magnitude of risk of a disease in a population Descriptive unit of magnitude of risk: Rate: incldence, prevalence, morbidity, mortality… Limitation: Absolute risk is not comparative. Absolute risk does not allow one to establish association between exposure and disease Incidence / incidence density Definition: 某段觀察時間內，單位時間中所有可能發生某特定事件的人發生該事件的率。 I：新病例數 P：觀察人數（有可能發生者才算） T：觀察期間 Cumulative incidence rate Definition: 某世代族群或某固定族群的人，經過某段觀察時間後，發生某事件﹙疾病﹚的人口佔該世代族群人口總數的百分比。 該事件﹙疾病﹚的發生情形，用以推估在族群中的任一人發生該事件或得該疾病的機率，也稱危險度﹙risk﹚。 當疾病或事件的發生機率很小時，累積發生率幾乎可等於發生率乘以年齡層距之總和。 2/（5-2/2） = 0.5 Relative Risk Definition: The ratio of the risk of disease in persons exposed compared to the risk of disease in persons unexposed Common formula of relative risk (RR) Interpretation of Relative Risk RR 1 - the risk of disease in the exposed group is greater than the risk in the unexposed group RR = 1 - the risk of disease is the same in the exposed and unexposed RR 1 - the risk of disease in the exposed group is less than the risk in the unexposed For Fixed Cohort In a prospective study, 8000 persons, including 3000 hypertensive and 5000 normtensive patients, were followed for 10 years. There were 84 and 87 CHD cases in hypertensive and normtensive persons, respectively. RR=? Answer: For Dyn