Project: Research project

Project Details


Self-Selection bias is a long-standing problem in Epidemiology. The
proposed research will apply new self-selection bias correction techniques
from econometrics to two epidemiological questions: (1) What is the effect
of excessive alcohol consumption on blood pressure? and (2) What is the
effect of schooling on blood pressure? While the suggested econometric
solutions have been widely used to address a variety of economic,
psychological, sociological and policy questions, the proposed study
appears to offer the first epidemiological applications. Data for both
applications will be drawn from the National Health and Nutrition
Examination Survey I, 1971-1975, (NHANES). (1) Excessive alcohol consumption and hypertension have been found to be
strongly correlated in a number of studies. The correlation is generally
thought to indicate that excessive alcohol use causes high blood pressure.
What statisticians refer to as the "constitutional or self-selection
hypotheses" (COSSH) may also explain the correlation, however. Heredity
may predispose individuals to high blood pressure and/or excessive alcohol
use. If hereditary factors cluster together in the same persons, we would
expect to observe a correlation between hypertension and excessive alcohol
use, but this correlation would not imply causation; it would only reflect
genetic clustering. The causation hypothesis is nevertheless difficult to
dismiss entirely. A handful of studies have provided evidence that, on
average, when excessive drinkers cut their consumption to zero for an
extended number of months their blood pressures fall. The real question
then is to determine what part of the observed correlation reflects the
causal relation and what part reflects unobserved genetic factors. (2) Studies have found an inverse relation between an individual's years
of schooling completed and blood pressure, other things equal.
Explanations for the correlation differ. Some have argued for a direct
effect whereby schooling enhances the "production of health." Others
assert that one or more "third variables" such as unobserved genetic or
personality factors affect both blood pressure and schooling the same
direction; this argument is essentially a self-selection explanation. The
second application will test if evidence from the NHANESI data provide more
support for the "production" of health argument or the self-selection
argument. If evidence for self-selection is obtained, policy
recommendations to increase funding on education to improve health are
Effective start/end date8/1/866/30/88


  • National Institutes of Health


  • Medicine(all)


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