Excess Winter Deaths: Review of the evidence
Summary
The UK, in common with other European countries, experiences higher levels of mortality
in the winter than in the Summer. Studies have found that mortality increases as mean
daily temperatures fall (below 18 degrees) [1] and in England and Wales, the total excess
winter mortality is estimated to be around 30,000 per annum [2]. Mortality in England and
Wales however, increases more than in other European countries with colder climates
(suggesting that factors other than temperature also contribute). There is no clear cut
explanation for excess winter mortality. It would appear to be due to a variety of factors.
Consequently, the response needs to be similarly multi-faceted.
Background






Excess winter mortality is only be partially explained by circulating influenza viruses
[7]
The effects of cold temperatures are more gradual than those seen with heat.
Cardiovascular deaths occur on average, two days after a cold peak, deaths from
respiratory disease occurring on average 12 days after a cold peak[10]
The increase in winter deaths is mainly due to the breakdown of the cardiovascular
or respiratory system, respiratory disease in particular shows the largest seasonal
fluctuations [1].
Seasonal mortality mainly affects those aged over 65 [1]. Of all those aged over 65,
the group aged 85+ had the largest variation between summer and winter mortality
[1].
In Europe, it is the countries with (relatively) the mildest winters which report the
greatest excess deaths. This has been termed the, ‘paradox of excess winter
mortality’, because in milder climates, there should in theory, be less potential for
cold strain and cold related mortality, but in fact there is more [11]
A study looking at the contribution of flu-like illnesses between 1989 and 1999,
found that on average, there are 12,554 excess winter deaths (in England) due to
flu [6]. The study also found that those who died were not simply those who were
likely to die in the next few months anyway (there was no dip following the Winter)
and that hospital admissions increased for respiratory infections (rather than
cardiovascular conditions) particularly in those aged 75 or over [6]
The evidence: temperature


Regression analysis indicates that around 88% of the variation in numbers of
excess Winter deaths per annum in England and Wales can be accounted for by
three variables: mean Winter temperature, number of Winter deaths registered to
influenza and time (contribution to Winter deaths by about 500 per year). The same
study also found an inverse relationship with rainfall and wind, which could be
explained by a reduction in outdoor activities when it is raining or windy which
prevents outdoor cold stress [8].
A recent article published in the BMJ suggested that the majority of the seasonal
fluctuation in mortality is related to cold (rather than influenza) [12].
Produced by Sarah Kinsella, NHS Wirral Performance & Public Health Intelligence Team
September 2009
D:\533566280.doc





A report into excess Winter deaths by the South East Public Health Observatory
(SEPHO) notes that there has been more focus on indoor temperature than on
preventing outdoor exposure. The report does also acknowledge that outdoor
temperature alone does not explain all excess Winter mortality, but points out that
excess Winter mortality has been falling since 1977, a fact they put down to
increasing car ownership, which greatly reduces exposure to outdoor cold stress
[15]
Keatinge et al (an experienced and long-standing researcher in the field of Winter
deaths), argues that much excess winter mortality arises from ‘brief excursions
outdoors, rather than low indoor temperatures’. He argues that campaigns remain
overly fixated on indoor heating, when the cold stress experienced from minutes
spend at a windy bus stop can exceed anything experienced indoors [13]. This point
of view is supported by research linking poor access to public transport and excess
Winter mortality and Keatinge argues that the time has come to look at physical
measures such as adequate bus shelters and in some cases, heated waiting
rooms/seating [13].
The evidence is still unclear as to why Britain has higher rates of winter mortality
than other European countries who have colder winters however. Several studies
found that people from regions with warmer winters tended to have cooler homes
and took less preventative measures against the cold- e.g. wearing inadequate
clothing for example [3]
The highest seasonal variation in mortality in Europe occurs in Portugal (28% above
average), Spain (21% above average) and Ireland (also 21% above average). The
UK’s excess Winter mortality is around 18%, the same as Greece. Compare this to
the Scandinavian countries who have very severe Winters, but much lower variation
(e.g Finland, only 10% above average). This has been termed the, ‘paradox of
excess Winter mortality’, because in milder climates, there should in theory, be less
potential for cold strain and cold related mortality, but in fact there is more [11].
It has been proposed that countries with higher excess Winter mortality are those
with large concentrations of the population living near to the sea (such as the UK,
Portugal and Italy). This has lead some researchers to hypothesise that the
transmission of viruses is influenced by coastal climatic conditions and the ambient
temperatures of typical British Winters to encourage greater transmission of viruses
(which then impact on mortality amongst vulnerable people) [5]
Evidence: socio-economic factors



It might be expected that there would be a link between cold exposure and
deprivation, but many studies fail to find a link between the two factors. In fact, it
was found in one study that people in the lowest socio-economic groups do not
necessarily live in cooler homes as housing association and local authority
dwellings tend to be well heated and well-insulated, whearas large owner-occupier
houses on the other hand, tend to be those which are harder to heat [9].
A study published in the BMJ recently concluded that socioeconomic factors were
not strongly associated with winter death in older people (in contrast to a recent
cross-European study detailed later in this report) [12].
Researchers have concluded that older age, female sex and a history of respiratory
illness confer more vulnerability (than deprivation) because deaths seem to be
widely distributed amongst older people generally rather than being heavily
concentrated amongst disadvantaged groups per se [12]. The authors also point out
that many other UK studies have also failed to find a socio-economic cause for
Winter mortality and suggest that because of this, fuel poverty relief alone may not
Produced by Sarah Kinsella, NHS Wirral Performance & Public Health Intelligence Team
September 2009
D:\533566280.doc




be enough to reach all those at risk because other (personal and behavioural)
characteristics are also important.
This assertion is also backed up by studies from Denmark which also failed to find
social gradients for Winter mortality (but do find it to be significantly associated with
being female, having respiratory disease and living alone) [14].
A Scottish study examining whether excess Winter deaths in Scotland were
correlated with the (Scottish) Index of Multiple Deprivation found a significant
positive correlation (p= 0.3, 95% CI) [4]
Socioeconomic factors were found to be associated with excess Winter mortality
across Europe, with those areas with the highest levels of income inequality (using
Gini co-effiecient and multiple deprivation scores) also having the largest variations
in seasonal mortality [11]. As mentioned above, although deprivation has been cited
as a factor in Scottish and pan-European studies, research carried out in England
has failed to find links.
Reliance on public transport however (feature of deprivation), is thought to increase
exposure to outdoor cold [9]
Evidence: vulnerable groups





Studies from Denmark (which failed to find social gradients for Winter mortality)
found it to be significantly associated with being female, having respiratory disease
and living alone [14].
The South East Public Health Observatory (SEPHO) report into excess Winter
Mortality notes that there is a significantly greater increase in excess Winter
mortality ratios for care home residents. As care home residents generally lead a
sheltered existence, protected from exposure to outdoor temperatures, damp
housing or difficulties with heating their homes, it might be expected that excess
Winter mortality would be low for this group, when in fact, the opposite is true
(another Winter mortality paradox). It is the case however, that people in care
homes are likely to be the very oldest older people, many will have pre-existing
conditions and they live in an enclosed space where infection can easily spread.
Greater excess mortality amongst this group may also reflect seasonal patterns in
care home use, for example, more patients being admitted to care homes shortly
before death in the winter period. Whatever the explanation (and there are many),
figures do demonstrate that the seasonal increase in mortality has a strong impact
on care home residents. The report notes that guidance for care homes has been
developed on dealing with heatwaves, and suggests that similar guidance for winter
might also be beneficial [15]
Instituting early prophylaxis with NI (neuraminidase inhibitor) anti-virals (such as
Tamiflu) amongst the very aged in residential and care home settings (because
influenza vaccination is less effective in this group than in the ‘healthy’ old). If
introduced, researchers have hypothesised that the spread of influenza could be
curtailed in institutional environments [5]
Vaccination of health care workers is important to limit spread of flu amongst
vulnerable patients in hospitals and other healthcare settings [5]
Results have shown that asthma patients without a written personal asthma action
plan are four times more likely to have to be admitted to hospital, due to an asthma
attack, than those who do. Currently only 16% of people with asthma in England
have a written personal asthma action plan [15].
Produced by Sarah Kinsella, NHS Wirral Performance & Public Health Intelligence Team
September 2009
D:\533566280.doc
Evidence: housing



Lack of central heating is associated with higher excess Winter mortality [8]
The large, cross-European study already referred to in this report found slightly less
robust relationships between energy efficiency levels and excess Winter deaths,
although they were still significant at the 5% level (cavity wall insulation, p=0.02,
double glazing p=0.02 and floor insulation p=0.03). The four countries with the
poorest standard of housing in this respect (Portugal, Greece, Ireland and the UK
all score highly for excess Winter deaths [11]. The authors suggest that their
findings support the theory that excess Winter mortality can be reduced through
socioeconomic progress (such as looking at poverty, income inequalities, fuel
poverty and deprivation) [11]
Standards of thermal insulation in housing have been linked as a potential
causative factor behind the ‘excess Winter mortality paradox’. A cross-European
study found that there is a relationship between GDP and excess Winter mortality,
with the four ‘cohesion’ countries’ [17] of the EU (Greece, Ireland, Spain and
Portugal) demonstrating the highest mortality (p<0.001) [11].
Evidence: personal and behavioural factors



One study suggests a protective effect for manual labour, which may explain the
fact that some of the lowest rates of excess winter mortality are amongst males in
social class V who are still working. This is also supported by a study from Russia,
which showed that as well as wearing layered, warm clothing when temperatures
fell, the local population increase their physical activity (and appear to experience
no increase in Winter mortality until temperatures fall below 0°, in Western Europe,
mortality starts to increase when temperatures fall below 18°). They concluded that
tackling fuel poverty alone is unlikely to produce wider health benefits as many
factors are involved in excess Winter mortality other than cold homes [15]
The recent cross-European study already mentioned found (perhaps surprisingly)
that lifestyle risk factors were not associated with excess Winter mortality (p=0.34),
unlike all year mortality rates [11].
Pre-seasonal vaccination has been shown to be effective in reducing the more
serious manifestations of influenza, as has vaccination of health care workers.
Campaigns to increase uptake of immunisation have been relatively successful
amongst target groups in the general population, but uptake amongst healthcare
workers remains poor [5]
Produced by Sarah Kinsella, NHS Wirral Performance & Public Health Intelligence Team
September 2009
D:\533566280.doc
Key Messages








Evidence on this topic suggests many different interventions may be beneficial, but
stops short of quantifying what level of reduction in mortality might be expected by
introducing various interventions. Risk reductions for example, are not calculated.
Measures to reduce both indoor and outdoor cold stress are necessary to reduce
levels of winter mortality. Warning people about outdoor cold exposure and
protective measures is as important as messages about keeping their home
adequately heated.
Measures should concentrate on vulnerable people (those living in care homes,
those aged over 65, those with respiratory or cardiovascular conditions, older
women, people reliant on public transport, sedentary people and older people who
live alone)
Early use anti-virals amongst the very aged in residential and care home settings
could limit the spread of influenza in institutional environments and therefore reduce
mortality [5]
Pre-seasonal vaccination (of the general population) has been shown to be
effective in reducing the more serious manifestations of influenza. The proportion of
health care workers vaccinated should be increased to limit spread of flu to
vulnerable patients in hospitals and other healthcare settings [5]
Guidance for care homes has been developed on dealing with heatwaves, similar
guidance for winter may be beneficial [11]
The introduction of asthma plans for affected patients may reduce admissions for
the condition [16]
The possibility of introducing heated waiting rooms/seating, wind-proof bus shelters
and similar could be investigated, especially in areas populated by high numbers of
older people who are reliant on public transport
References
1. Johnson H & Griffiths C. Estimating excess Winter mortality in England and Wales.
Office for National Statistics. Winter 2003.
2. Hughes, S., Bellis, M., A., Bird, W., Ashton, J. R., 2004. Weather forecasting as a
public health tool. Centre for Public Health. Available at:
http://www.cph.org.uk/showPublication.aspx?pubid=151
3. Pattenden, S et al. Mortality and temperature in Sofia and London. J Epidemiology
and Community Health 2003;57:628-633
4. Howieson SG & Hogan M. Multiple Deprivation and excess Winter deaths in
Scotland. Journal of the Royal Society of Health. January 2005, Vol 125 (1); 18-22.
5. A Winters Tale: coming to terms with Winter respiratory illness. Health Protection
Agency. 2003
6. Fleming, DM. The contribution of influenza to combined acute respiratory infections,
hospital admissions and deaths in Winter. Commun Dis Public Health; 3:32-38
7. Ballester F et al. Weather, climate and public health. J Epidemiol Community Health
2003;57:759-760
8. Aylin P et al. Temperature, housing, deprivation and their relationship to excess
Winter mortality in Great Briatin, 1986-1996. Interntational Journal of Epidemiology
2001; 30:1100-1108
9. Hajat S et al. Heat-related and cold related deaths in England & Wales: who is at
risk? Occup Environ Med 2007; 64: 93-100
10. Hughes S et al. Weather forecasting as public health tool. Centre for Public Health.
Liverpool John Moores University 2004
Produced by Sarah Kinsella, NHS Wirral Performance & Public Health Intelligence Team
September 2009
D:\533566280.doc
11. Healy JD. Excess Winter mortality in Europe: a cross country anaylsis identifying
key risk factors. J Epidemiol Community Health 2003;57:784-789
12. Wilkinson et al. Vulnerability to Winter mortality in elderly people in Britain:
population based study. BMJ online. Doi 10.1136/bmj.38167.589907.55
13. Keatinge W. Winter deaths: warm housing is not enough. BMJ 2001;323:166 (July)
14. Rau R. Winter mortality in elderly people in Britain. BMJ 2004;329:976-077 (23 Oct)
15. Dinsdale H et al. Technical Report: Excess Winter Mortality. South East public
Health Observatory. February 2006. ISBN 0-9542971-5-6
16. Asthma UK ref
17. The four cohesion countries (in 2002) were defined as having a GDP per head
which was 90% lower than the EU average, large parts of their territory defined as a
‘less favoured region’, a traditional manufacturing structure, low productivity and a
reliance on agriculture for employment
Appendix 1
Table : Deaths in people aged ≥65 by any cause occurring between 1 Aug 1986 and 31
July 1996 (excluding 1989/90 ‘flu epidemic year) in Great Britain and odds of death in
Winter, by age band [8]
Cause
All causes
CHD
Stroke
Respiratory disease
OR
1.127
1.145
1.119
1.485
65-74
95% CI
1.114-1.139
1.120-1.1170
1.084-1.156
1.441-1.530
OR
1.180
1.179
1.153
1.506
75-84
95% CI
1.167-1.193
1.154-1.204
1.118-1.189
1.463-1.550
OR
1.252
1.217
1.178
1.577
85+
95% CI
1.238-1.267
1.191-1.245
1.142-1.216
1.532-1.623
Produced by Sarah Kinsella, NHS Wirral Performance & Public Health Intelligence Team
September 2009
D:\533566280.doc