Winter mortality

The purpose of the winter mortality measure is to compare the number of deaths that occurred in the winter period (December to March) with the average of the non winter periods (August to November and April to July). Winter mortality is not solely a reflection of temperature, but of other factors as well. These include respiratory diseases and pressure on services, which have been more intense than usual during and following the height of the pandemic. [1]

Excess winter deaths are defined as the difference between the number of deaths which occurred in winter (December to March) and the average number of deaths during the preceding four months (August to November) and the subsequent four months (April to July). The winter mortality index (WMI) is a measure expressed as a ratio of the difference in all cause mortality during winter months compared to the average in the non winter months. [2]

The terminology used to describe this indicator has changed to provide clearer explanation of what the analysis represents. The measures have been renamed to winter deaths compared to non winter deaths (previously excess winter deaths) and winter mortality index (WMI) (previously excess winter mortality index). There have been no methodology changes.

The winter mortality index (WMI) is a measure expressed as a ratio of the difference in all cause mortality during winter months (December to March) compared to the average in the non winter months (the preceding August to November and following April to July).

Key findings

• During the period August 2021 to July 2022, in the Lancashire-12 area an estimated 450 more deaths occurred in the winter period (December 2021 to March 2022) compared with the average of the non-winter periods; this is lower than the count of 1,080 deaths for the winter period of December 2020 to March 2021.
• In the Lancashire-12 area, the all-age WMI (10.0%) is similar to the England WMI (8.1%) (Aug-21 to July-22). 

1 ONS Statistical Bulletin: Winter mortality in England and Wales:2021 to 2022 (provisional) and 2020 to 2021 (final)

2 ONS: Winter mortality in England and Wales (QMI)

For county, district and unitary data please see below.

Page updated February 2024