Original article
Sample size determination in case-control studies: The influence of the distribution of exposure

https://doi.org/10.1016/0021-9681(85)90044-XGet rights and content

Abstract

In the design of case-control studies, the determination of the required number of cases and controls is based on consideration of the strength of the relationship between the disease and exposure to the putative cause, the variability in exposure within the population under study, and the desired size and power of the statistical test. This paper derives sample size equations for studies with a continuous exposure which allow the investigator to specify the strength of the relationship between disease and exposure in terms of relative risk, etiologic fraction or the slope of an exposure response relationship. With these formulations it becomes apparent that the size of the sample increases with decreasing variability in exposure in the population under study, a finding not apparent in the use of conventional methods of sample size determination for continuous data. The ability of a case-control study to detect a significant association between disease and exposure therefore depends critically on the distribution of exposure which exists in the community to be studied. Implications of these findings for studies of diet and cancer are discussed.

References (22)

  • RM Kay et al.

    Multivariate analysis of diet and serum lipids in normal men

    Am J Clin Nutr

    (1980)
  • T Colton

    Statistics in Medicine

    (1974)
  • J Fleiss

    Statistical Methods for Rates and Proportions

    (1981)
  • M Jain et al.

    A case-control study of diet and colo-rectal cancer

    Int J Cancer

    (1980)
  • RL Phillips

    Role of life-style and dietary habits in risk of cancer among Seventh-day Adventists

    Cancer Res

    (1975)
  • J Higginson

    Etiological factors in gastrointestinal cancer in man

    J Natl Cancer Inst

    (1966)
  • B Modan et al.

    Low-fiber intake as an etiologic factor in cancer of the colon

    J Natl Cancer Inst

    (1975)
  • LG Dales et al.

    A case-control study of relationships of diet and other traits to colorectal cancer in American Blacks

    Am J Epid

    (1979)
  • S Graham et al.

    Diet in the epidemiology of cancer of the colon and rectum

    J Natl Cancer Inst

    (1978)
  • EL Wynder et al.

    Environmental factors of cancer of the colon and rectum. II. Japanese epidemiological data

    Cancer

    (1969)
  • W Haenszel et al.

    A case-control study of large bowel cancer in Japan

    J Natl Cancer Inst

    (1980)
  • Cited by (38)

    • Association of health and lifestyle factors with uterine fibroids among Saudi women: A case–control study

      2022, Journal of Taibah University Medical Sciences
      Citation Excerpt :

      The sample size was calculated with OpenEpi (Open Source Epidemiologic Statistics for Public Health Version 2.3.1) by using the methods of Kelsey et al. and Fleiss, with a continuity correction (see Supplementary file).19,20 Assuming a 95% confidence level (Zα), power (1-β) of 80% (Zβ), ratio of controls to cases: 1:1 (r), proportion of controls exposed to diabetes of 13.8% (P1),21 hypothetical proportion of cases exposed to diabetes of 24.25% (P2) and odds ratio of 2.0,22 we calculated necessary sample sizes of 239 cases and 239 controls. Cases were defined as women with a confirmed UF diagnosis identified by a radiologist through lower abdominal ultrasound examination or pelvic ultrasound.

    • Response

      1991, Journal of Clinical Epidemiology
    • Sample size determination in case-control studies

      1991, Journal of Clinical Epidemiology
    View all citing articles on Scopus

    Present address: Department of Preventive Medicine, University of Southern California, Los Angeles, CA 90007, U.S.A.

    View full text