I have already published my paper “A Study of Factors Influencing the Morbidity Rate of Typhoid Fever in Japan from the Standpoint of Vital Statistics. ” In the present communication I attempted an inquiry into the relationship between the morbidity rate of dysentery (including Ekiri) and factors of vital statistics affecting it according to geographical districts. In this study I adopted again the method of partial correlation, in the same way as in the previous rep DA. The factors taken into consideration, and their notations, are given below;
y=Morbidity rate of dysentery
=log (Number of cases of dysentery / Population 100, 000)
d=Density of population=log (Population / Area of Land in km
2)
s=Sex ratio of pupulation=Numbar of male to 100 female
a=Mean temperature (chiefly at the site of a pref ctural office; if not, in the neighbourhood of it)
b=Distributioa of wealth
= Amount of postal savings/ Population
c=Urbanlzation=log (Ponulation in cities / Total pupulation 1, 000)
g=Prevalence of education= Number of graduates of girls/ Female Population and training schools
h=Age composition of population
= Population over 60 years of age / Total Population
f=Number of persons per family= Population/ Number of families
p=Population
The data appointed are those of the year 1930, when the latest national census was taken.
1.
Density of population (d) and morbidity rate of dysentery (y).
It is not unreasonable to presume that the denser the population the morbidity rate of infectious diseases may be. As I expected, I found a posive, significant correlation between d and y,
If the infuence of other factors is eliminated, however, the above turns out to be aninsignificant coeffieient,
This shows that the density of population itself is not responsible for the increase in the morbidity rate c f dysentery. The original correlation of the first order between y and d must be accordingly interpreted as due to the other factors. Among such factors mean temperature (a) is important. The dense: the population, the higher is the mean temperature, and the mean temperature is a factor which iufluences greately the morbidity rat 2 of dysentery.
Thus we see that the coefficient of the first order comes out as significant.
2.
Number of persons per family (f) and morbidity rate of dysenteiy (y).
If the correlation between y and f are computed, the following coeffi -cient is obtained, which shows that prefectures having a larger number of persons per family have a lower morbidity rate.
This is a result quite contrary to our expectation. This original co ffiient must be due to the fact that districts having a larger number c of persons per family have a lower mean temperature and a smaller age composition over 60 years of age, while a and h are the factors which increase greatly the morbidity rate of dysentery. So we see the correlation coeffcient between f and y are negative. If the other factors are held constant, the coefficient of net correlation becomes positive and significant
It means that the number of persons per family is an important factor influencing the morbidity rate of dysentery.
3.
Urbanization (c) and the morgidity rate of dysentery (y).
I have not been able to find out any reliable survey about the distribution of dysentery in the urban and rural districts. Anyway we obtain from computation,
which is not significant, but yet positive. The influence of other factors being eliminated, we obtain the coeffcient,
That is to say, in Japan urbanization itself exerts no great influence upon the morbidity rate.
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