Demographic and Epidemiological Studies

J. Lederberg and W. Bodmer

Maternal Age and Birth Order are known to play an important role
in the incidence of chromosome anomalies which are in turn responsible
for some of the most severe forms of mental retardation. However
relatively little is known in detail about the demography of child
spacing in the overall population which is quite important in every new
survey of factors involved in chromosome anomaly. We are therefore continuing
our collaborative study with the United States Bureau of the Census to
establish the standard reference for this type of information from the 1960
Population Census.

In recent years there have been repeated claims of the epidemicity
of chromosome disease. The best known of these comes from the studies on
mongolism in Victoria by Collman and Stoller. Unfortunately these studies
have not been subjected to the rather difficult statistical analysis which
is appropriate for the analysis of clusters. Our computer simulations of
the Australian data fail to support the published claims of a statistically
significant clustering of cases it is therefore necessary to approach such
assertions that this is evidence for a viral etiology of the disease with
great caution. It should be emphasized that the statistical procedures
needed to authenticate non-random deviations in time series are still
controversial and this is one of the reasons it has been necessary to resort
to a computer simulation. In addition a scrutiny of the data of admissions to
the Pomona State Hospital failed to verify any similar clustering of cases
although it must be admitted that there are many possible points of inter-

ference as between the occurrence of the cases and their admission to the

hospital,

Most specific claims of association between nondisjunction and epidemics
of particular diseases have been made and we are following these up to the

extent that the available data permits.