J Irish Med Assoc 55:17-18 (July) 1964
The Influence of Water Hardness and Rainfall on the
Incidence of Cardiovascular and Cerebrovascular Mortality in
Ireland
Risteárd Mulcahy, M.D., M.R.C.P.(Lond.),
Cardiac Department and Dept. of Preventive Medicine, St.
Vincent’s Hospital, Dublin, 2.
SCHROEDER (1960a & 1960b) showed that there was a
significant negative correlation between hardness of water and
death rates from coronary heart disease and hypertensive heart
disease in 163 urban areas in the United States of America. There
was a less significant negative correlation with cerebrovascular
disease and generalised arteriosclerosis. In other words,
hardness of water seemed to have a protective action against
these conditions. This type of epidemiological study was
originally done by Kobayashi (1957) of Japan who showed
variations in death rates from specific causes in different areas
which correlated with certain geological features.
Morris, Crawford and Heady (1961) show negative correlations
between water hardness and (1) total cardiovascular mortality,
(2) deaths caused by vascular lesions of the central nervous
system, (3) deaths certified as "myocardial degeneration", and
(4) deaths in middle aged men caused by coronary heart.disease.
There appears to be a significantly higher death rate under these
four classifications in the soft water areas of England and
Wales.
The hardness of water of the 15 largest urban areas in the
Republic of Ireland was determined. These figures are shown in
Table I with population figures for these 15 areas. Figures for
annual average rainfall were also included in view of the
statement by Morris et al. (1962) that rainfall, softness of
water and cardiovascular mortality are highly associated.
Generally the greater the rainfall the softer the water supply.
The death rates for the period 1957-1961 inclusive for the
following causes were also obtained for these areas:
(1) arteriosclerotic heart disease (IDL 420).
(2) arteriosclerotic heart disease and "myocardial
degeneration" (IDL 420 and 422).
(3) total cardiovascular mortality (IDL 400-443).
(4) cerebrovascular mortality (IDL 331, 332, 334).
Table II shows the correlation of (1) hardness of water, and
(2) average annual rainfall with the death rates for the above
causes in all age groups and in the age group 35-64.
Results
None of these correlations approaches the level at which they
can be considered as differing significantly from zero. The
number of pairs of values, in each case, is only 15 and for so
few observations the estimated coefficients of correlation would
need to be outside the range of -0.514 to +0.514 to indicate a
significant deviation at the 5% level.
It is clear from these results that local geological and
climatic conditions do not appear to play an important part in
determining the incidence of cardiovascular disease in the
Republic of Ireland. This conclusion contradicts the findings
reported from Japan, the United States, and England and
Wales.
As in other countries there arc substantial variations in the
certified incidence of death from various causes in the different
cities and towns of Ireland. Table III illustrates this variation
in the average annual death rate (1957-1961) for arteriosclerotic
heart disease and "myocardial degeneration" (IDE 420 and 422) in
the 15 largest urban areas. Unlike the findings in England and
Wales, water hardness and rainfall do not appear to play part in
determining these wide variations.
Summary
The total hardness of water, average annual rainfall and death
rates from cardiovascular and cerebrovascular disease have been
determined for the 15 largest urban areas in the Republic of
Ireland.
Hardness of water and rainfall appear to play no part in
determining the incidence of death from these causes.
These conclusions contradict the recent findings reported from
Japan, the United States of America and Great Britain.
Acknowledgments
I am grateful to the Director of the Central Statistics
Office, Dr. Donal McCarthy, and to his staff for supplying most
of the information required for this study and for the analysis
of the results. I am also grateful to the Secretary of the
Department of Transport and Power for information on average
annual rainfall. I wish to thank the engineers in charge of the
Waterworks Departments of Dublin Corporation and Drogheda
Corporation for their assistance.
References
Kobayashi, J. (1957). Ber. Ohara Inst.,
11, 12.
Morris, J. N., Crawford, M. D. and Heady, J. A. (1961).
Lancet, 1, 860.
Morris, J. N., Crawford, M. D. and Heady, J. A. (1962),
Lancet, 2, 506.
Schroeder, H. A. (1960a) J. Amer. med. Assn.,
172, 1902.
Schroeder, H, A. (1960b) J. chron, Dis.,
12, 586.
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