Some effects of within-person variability in epidemiological studies

https://doi.org/10.1016/0021-9681(73)90013-1Get rights and content

Abstract

When individuals with high levels of a biological variable are given a treatment to lower these levels, it is important to be able to assess how much of any subsequent decrease is due to the treatment. The fact that individuals selected for their high levels on one occasion will (on average) show lower levels on subsequent occasions even in the absence of treatment is now recognized, and has been termed the ‘regression’ effect. The reverse is true for low levels.

This paper presents a method for predicting how much change can be expected from regression, and thus a means of estimating the treatment effect. The analysis is based on measures of within-person and between-person variability, the within-person source being responsible for the regression effect. The effect that within-person variability has on misclassification of people into high-risk groups, and a means of determining how many estimates of one individual's level are required for a given precision of classification, are also derived from the same analytical approach.

Examples are given using data on cholesterol levels following treatment with Clofibrate, caloric intake levels in a diet survey, and the relationship between the incidence of ischemic heart disease and systolic blood pressure level.

References (16)

There are more references available in the full text version of this article.

Cited by (181)

  • Symptom Variability and Early Symptom Regression in the MAPP Study: A Prospective Study of Urological Chronic Pelvic Pain Syndrome

    2016, Journal of Urology
    Citation Excerpt :

    We advocate for awareness of RTM and other causes of early symptom regression in the design and analysis of studies of UCPPS. Several strategies exist to deal with RTM in observational and interventional research.9 They include the use of placebo controlled, randomized trials or characterizing subjects during a pre-enrollment screening based on multiple measurements.11

  • Epidemiology and Consequences of Childhood Hypertension

    2008, Comprehensive Pediatric Nephrology: Text with CD-ROM
  • Epidemiology and Consequences of Childhood Hypertension

    2008, Comprehensive Pediatric Nephrology
View all citing articles on Scopus

Now at University of Southampton, Southampton, England.

View full text