CONCURRENCE OF MONTHLY VARIATIONS OF MORTALITY RELATED TO UNDERLYING CAUSE IN EUROPE

Study objective - The study aimed to examine the concurrence in the va riation of monthly numbers of deaths in summer and winter from the fou r main underlying causes - respiratory, circulatory, neoplastic, and a ll others - in four countries. In particular, the hypothesis that most non-respiratory concurrent deaths are miscoded respiratory deaths and that a large proportion of the winter mortality currently attributed to circulatory disorders should be attributed to respiratory causes wa s considered. Design - Mortality data were analysed graphically in rel ation to cause. Each of the four series of monthly data underwent time series analysis to remove autocorrelation, seasonality, and secular t rends. Associations between paired causes of death and between multipl e series (using Kendall's coefficient of concordance) were then examin ed after modelling. Setting - Monthly deaths (65 years and over) relat ed to underlying cause were examined for England and Wales (nine years ), The Netherlands (nine years), Denmark (10 years), and Portugal (10 years - all ages). Weekly data for England and Wales (51 weeks) were a lso analysed. Main results - All combinations of monthly deaths relate d to underlying cause were strongly associated in all four countries. This concurrence was evident down to the lowest monthly values so that all seasonally related deaths above the minimum monthly value can be used as an estimate of the ''concurrent'' proportion. Associations inv olving deaths from neoplasm were weakest. Concurrence was evident even on a weekly analysis (England and Wales). Concurrent deaths in Englan d and Wales accounted for 31.1% of respiratory, 16.0% of circulatory, 3.5% of neoplastic, 14.1% of deaths from other causes, and 14.2% for a ll deaths combined. The equivalent percentages for concurrent deaths f rom all causes were 8.4% in the Netherlands, 9.3% in Denmark, and 16.8 % in Portugal. Conclusions - Concurrence, which was present in each of the underlying causal groups in each of the four national data sets e xamined, suggests a common cause separate from the underlying cause th at has been used in the presentation of mortality statistics. If the p erson concerned had not died at that time, as a result of this cause, he would not have died from the recorded underlying cause. Most of the se non-respiratory concurrent deaths are miscoded. As a consequence, a large proportion of winter mortality currently attributed to circulat ory disorders should be attributed to other causes, probably respirato ry. More intensive research into the contribution made by acute respir atory diseases is proposed. The proportion of concurrent deaths varied in the four countries thereby limiting the validity of simple compari sons of national morality statistics.