Curtis C R, Erb H N, Kranz J M
J Dairy Sci. 1987 Feb;70(2):373-80. doi: 10.3168/jds.s0022-0302(87)80019-x.
Many dairy scientists are not familiar with epidemiologic study designs and measures. The various designs (cross-sectional, case-control, cohort) are reviewed with special reference to their strengths and weaknesses. Epidemiologic measures (incidence and prevalence rates, relative risk, odds ratio, attributable fraction, and population attributable fraction) are defined, and their validity in the contexts of the different study designs is discussed. Incidence rate (risk of disease) is the number of new cases of a disease divided by the population at risk during a specified time period. Prevalence rate is the frequency of both new and old cases in a population at a specified point or period in time divided by the average population during that same period. Both incidence and duration of disease contribute to prevalence. Odds ratios and relative risks are measures of association (how much disease the exposed group experienced relative to the nonexposed group) and are used to assess the relative importance of risk factors. Attributable fraction is the proportion of the incidence in the exposed group that can be attributed to the specific exposure. Population attributuable fraction is the expected reduction in incidence in the whole population if the specific exposure were prevented. The attributable fractions are useful in planning preventive and herd health programs.
许多乳品科学家并不熟悉流行病学研究设计和测量方法。本文回顾了各种设计（横断面研究、病例对照研究、队列研究），并特别提及了它们的优缺点。定义了流行病学测量方法（发病率、患病率、相对风险、比值比、归因分数和人群归因分数），并讨论了它们在不同研究设计背景下的有效性。发病率（疾病风险）是指在特定时间段内，新发病例数除以处于发病风险的人群数量。患病率是指在特定时间点或时间段内，某人群中新发和既往病例的频率除以同期平均人口数。疾病的发病率和病程都会影响患病率。比值比和相对风险是关联度的测量指标（暴露组相对于非暴露组经历了多少疾病），用于评估风险因素的相对重要性。归因分数是指暴露组发病率中可归因于特定暴露的比例。人群归因分数是指如果预防了特定暴露，整个人群发病率预期下降的比例。归因分数在规划预防和群体健康计划中很有用。
