Biomaterial Database

Methodological issues in cohort studies. II: Power calculations. 1988

G R Howe, and A M Chiarelli

NCIC Epidemiology Unit, University of Toronto, Ontario.

A simple model is described for estimating power in cohort studies, in which the exposure is treated as a polytomous variable, with a known distribution in the population from which the sample is drawn. The model then requires the specification of the expected number of deaths which will occur in the cohort, calculated from the population rates, the dose-response relationship, and the size of the cohort. The model also allows for misclassification of exposure, the rule rather than the exception in epidemiological studies. The model is applied to a proposed study of saturated fat intake and risk of death from colorectal cancer in a male cohort drawn from the general population. It is demonstrated that this approach leads to an optimization of the power estimates, and in particular that maximization of power can be achieved by using a relatively small number of categories, eg four. It is also demonstrated that the effect of misclassification is less extreme if a polytomous dose-response model is used for analysis as compared to the usual simple dichotomous exposure model.

UI	MeSH Term	Description	Entries
D008297	Male		Males
D008875	Middle Aged	An adult aged 45 - 64 years.	Middle Age
D008962	Models, Theoretical	Theoretical representations that simulate the behavior or activity of systems, processes, or phenomena. They include the use of mathematical equations, computers, and other electronic equipment.	Experimental Model,Experimental Models,Mathematical Model,Model, Experimental,Models (Theoretical),Models, Experimental,Models, Theoretic,Theoretical Study,Mathematical Models,Model (Theoretical),Model, Mathematical,Model, Theoretical,Models, Mathematical,Studies, Theoretical,Study, Theoretical,Theoretical Model,Theoretical Models,Theoretical Studies
D011336	Probability	The study of chance processes or the relative frequency characterizing a chance process.	Probabilities
D012004	Rectal Neoplasms	Tumors or cancer of the RECTUM.	Cancer of Rectum,Rectal Cancer,Rectal Tumors,Cancer of the Rectum,Neoplasms, Rectal,Rectum Cancer,Rectum Neoplasms,Cancer, Rectal,Cancer, Rectum,Neoplasm, Rectal,Neoplasm, Rectum,Rectal Cancers,Rectal Neoplasm,Rectal Tumor,Rectum Cancers,Rectum Neoplasm,Tumor, Rectal
D003110	Colonic Neoplasms	Tumors or cancer of the COLON.	Cancer of Colon,Colon Adenocarcinoma,Colon Cancer,Cancer of the Colon,Colon Neoplasms,Colonic Cancer,Neoplasms, Colonic,Adenocarcinoma, Colon,Adenocarcinomas, Colon,Cancer, Colon,Cancer, Colonic,Cancers, Colon,Cancers, Colonic,Colon Adenocarcinomas,Colon Cancers,Colon Neoplasm,Colonic Cancers,Colonic Neoplasm,Neoplasm, Colon,Neoplasm, Colonic,Neoplasms, Colon
D004041	Dietary Fats	Fats present in food, especially in animal products such as meat, meat products, butter, ghee. They are present in lower amounts in nuts, seeds, and avocados.	Fats, Dietary,Dietary Fat,Fat, Dietary
D004812	Epidemiologic Methods	Research techniques that focus on study designs and data gathering methods in human and animal populations.	Epidemiologic Method,Epidemiological Methods,Methods, Epidemiologic,Epidemiological Method,Method, Epidemiologic,Method, Epidemiological,Methods, Epidemiological
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000328	Adult	A person having attained full growth or maturity. Adults are of 19 through 44 years of age. For a person between 19 and 24 years of age, YOUNG ADULT is available.	Adults