A chill wind

(Nov 27, 2015)

In a previous blogs I have looked at seasonal fluctuations in mortality, usually with lower mortality in summer and higher mortality in winter.  The subject of excess winter deaths is back in the news, as the UK experienced heavy mortality in the winter of 2014/15, as demonstrated in Figure 1.

Figure 1. Excess winter deaths in England & Wales. Source: ONS.

Excess mortality in England & Wales

Figure 1 shows some important features, but some are less immediately obvious than others.  The most obvious feature is that the winter of 2014/15 is indeed the worst for excess winter deaths for fifteen years.  Another obvious feature of Figure 1 is that it is the elderly who bear the overwhelming brunt of excess winter mortality.  However, there is an easily…

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Tags: season, influenza, winter, frailty, mortality plasticity

Winter mortality

(Jan 29, 2009)

In previous posts we looked at seasonal fluctuations in mortality.  Since the UK is about to experience some particularly cold weather again, we will look at winter mortality in more detail.

The Office for National Statistics in England and Wales produces statistics comparing the mortality of three winter months with three summer ones.  These statistics take the form of excess numbers of deaths in winter, as shown in the graph below:

Excess winter mortality

As can be seen in the above graph, it is the elderly who bear the brunt of excess winter mortality.  There are a number of reasons for this, of which one of the best known is influenza, which is particularly infectious during winter months.  Influenza can kill directly, but it often…

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Tags: season, influenza, winter

Seasonal patterns in mortality

(Aug 17, 2008)

During an analysis of a large annuity portfolio we took some time out to look at the pattern of mortality by season as well as the overall time trend. We fitted a model for age, gender and season, where the definition of season is that used by the ONS: each season covers three months, and where winter covers December, January and February. The results are shown below, where the mortality index has a value of 100 in January 1998.

Seasonal patterns and time trend for mortality

The chart shows a number of interesting features. Most obviously, there is a strong downward trend, reflecting the ongoing significant improvements in annuitant mortality in the United Kingdom.

The next feature is the strong cyclic intra-year patter: high mortality in winter months, followed…

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Tags: mortality, annuities, season, time-trend

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