London's Pulse: Medical Officer of Health reports 1848-1972
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Hints from the Health Department. Leaflet from the archive of the Society of Medical Officers of Health. Credit: Wellcome Collection, London
London County Council 1956
[Report of the Medical Officer of Health for London County Council]
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Table v—
| All causes | Bronchitis | Other respiratory | Lung cancer | Other cancer | Cardiovascular | ||
|---|---|---|---|---|---|---|---|
| (a) | (b) | (c) | (d) | (e) | (f) | ||
| (1) Percentage in Social classes IV and V | M | 0.485 | 0.453 | 0.556 | 0.707 | 0.442 | 0.572 |
| F | 0.547 | 0.480 | 0.265 | —0.025 | 0.641 | 0.474 | |
| (2) Percentage born in London | M | 0.532 | 0.828 | 0.193 | 0.710 | 0.398 | 0.681 |
| F | 0.707 | 0.848 | 0.252 | —0.144 | 0.736 | 0.738 | |
| (3) Index of smoke | M | 0.645 | 0.680 | 0.169 | 0.511 | 0.368 | 0.632 |
| F | 0.688 | 0.715 | 0.271 | —0.076 | 0.668 | 0.845 | |
| (4) Index of sulphur dioxide | M | 0.514 | 0.037 | 0.579 | 0.274 | 0.193 | 0.477 |
| F | 0.334 | 0.408 | 0.903 | 0.249 | 0.153 | ||
All coefficients positive unless preceded by a minus sign.
5 per cent, level of significance with 8 pairs of variables r = 0.707
With only eight pairs of variables the value of the correlation coefficient has to be
high (0.707) to reach a 5 per cent, level of significance. In only comparatively few
instances do the values in the above table reach this level, they are:—
Per cent. in social classes IV and V and lung cancer—males.
Per cent. born in London and all causes—females.
Per cent. born in London and bronchitis—males.
Per cent. born in London and bronchitis—females.
Per cent. born in London and lung cancer—males.
Per cent. bom in London and other cancer—females.
Per cent. born in London and cardio-vascular diseases—females.
Index of smoke and bronchitis—females.
Index of smoke and cardio-vascular causes—females.
Index of sulphur dioxide and lung cancer—females.
While these numerical expressions of association do not necessarily represent a causal
relationship nevertheless it is worthy of comment that the percentage born in London
is mentioned six times (counting each sex separately), index of smoke twice, index of
sulphur dioxide once and percentage in social classes IV and V once. The obvious
implication is that percentage born in London, as representing duration of life spent in
London, has more bearing on mortality than any of the other indices listed.
It will be appreciated that the various factors do not operate in isolation. Hewitt
(1956) combined the index of sulphur dioxide with the percentage born in London
to arrive at a composite index for the measurement of the degree of the atmospheric
pollution and duration of exposure thereto, and found a significant correlation between
deaths from all causes, respiratory causes, bronchitis, cancer of the lung and heart
disease in the nine health divisions of London. A similar approach has been made with
the data in this investigation by combining the percentage born in London with each
of smoke and sulphur dioxide in relation to bronchitis. Bronchitis was chosen because,
as can be seen from Table V, there is a significant correlation with the percentage London
born of either sex, a reasonable correlation with smoke and virtually none with sulphur
dioxide. The results are as shown below:—
Bronchitis and percentage born in London X smoke
males r = +0.824.
females r = + 0.836.
Bronchitis and percentage bom in London x sulphur dioxide
males r = + 0.818.
females r = + 0.800.