疾病的分布 (哈医大《流行病学》).ppt

What is Distribution of Disease☆ When  ☆ Where ☆ Who INTRODUCTION 疾病的分布是指疾病的人群现象 是描述疾病事件（发病、患病、死亡等） Time （时间） Place （空间） Person（人间） 在流行病学中简称“三间分布” Example You have been asked to investigate an event in which 2,220 people were exposed and 1,520 of them died. Your role as an epidemiologist is to ask questions about person, place and time. Example How do we ask questions?Surveys-of survivors--of other related persons Objectives 第一节疾病频率测量指标 第二节 疾病流行强度 第三节 疾病分布形式 Frequency of Disease Measurement Intensity of Epidemic Dimension distributions of disease 第一节 疾病频率测量指标 Directions: This chapter describes the basic measures of disease frequency used in epidemiologic research 发病频率测量指标 患病频率测量指标 死亡频率测量指标 预期寿命及相关指标 一、发病指标 发病率（incidence） 罹患率（attack rate） 续发率（secondary attack rate） 发病率（incidence） 定义 在一定期间内，一定人群中某病新发生的病例出现的频率。 Definition the rate of new cases of a disease in a specified population over a defined period Incidence rate Numerator New (incident) cases appearing during a time period (usually one year) Denominator Average population during the time period Midpoint population estimate Cases per 10X per year Example: 234 per 100,000 per year 罹患率（attack rate） 定义 在某一局限范围，短时间内的发病率。观察时间可以日、周、旬、月为单位。 Definition the proportion of a population affected by the disease during a prescribed, usually short, period of time. Incidence rate and attack rates An outbreak of hepatitis A in Ajloon from March 1 to march 14 2000 had an attack rate of 25 per 1000 The yearly incidence rate of hepatitis A . in Ajloon is 238 per 100,000 per year How do you compare these rates? Is their an outbreak?Incidence and attack rates compared 1. Adjust population to make rates comparable Divide 238 per 100,000 by 100 2.38 per 1000 per year 2. Adjust time period 2 weeks = 2/52 year 2.38 (2/52) = 0.11