Cold and Health
James Goodwin
Head of Research
Hippocrates 400BC
On airs, waters, and places
• Whoever wishes to investigate
medicine properly, should proceed
thus:
in the first place to consider the
seasons of the year, and what
effects each of them produces for
they are not at all alike, but differ
much from themselves in regard to
their changes.
• Secondly he must study the warm
and the cold winds, both those
which are common to every country
and those peculiar to a particular
locality …
Five Vital Questions
•
•
•
•
•
Why does health deteriorate in the winter?
Does age make a difference?
What is ‘Excess Winter Mortality’?
What are its causes?
Can we do anything about it?
(1) Why does health deteriorate in the winter?
Why does health deteriorate in
the winter
• Ill-health is associated with a number of
winter factors, notably reducing photoperiod and cold temperature
• We have tropical physiology
• Darkness is associated with emotional
responses and mental health
• Cold is associated with physical and
psychological responses
(2) Does age make a difference?
Does age make a difference?
• Vulnerability to cold increases with age:
– Declining immune system
– Lower physiological reserve
– Slower and less precise bodily responses,
particularly temperature control, respiratory
and cardio-vascular systems
• The change is progressive and variable
but real decrements start at about 75
years and accelerate thereafter
Cold Exposure and Physiological Responses I
Young subjects
(n=11)
Old subjects
(n=11)
Cold Exposure and Physiological Responses II
Young subjects
(n=11)
•
Old subjects
(n=11)
◦
a
e
r
Skin Temperature (Finger) in Young (n=9) and Elderly (n=9)
Subjects at 6 and 21C
2
o
m C
e
T
3
0
2
8
2
6
2
4
2
2
2
0
1
8
1
6
1
4
1
E
o
C 2
Y
E
2
0
4
0
6
0
%
C 2
f
f
2
0
o
Y
p
3
T
o
C
f
o
f
T
C
1
1
6
T
6
8
2
m
T
0
V
Oa
x
(3) What is ‘Excess Winter Mortality’?
Excess Winter Mortality
• EWM is the number of deaths occurring between 1st
December and 31st March less the number of deaths in the
rest of the year
• Since 1841 there have been approximately 3 million
avoidable deaths in the older population in the winter
• For every 1◦C reduction in the average ambient
temperature in the winter, there are 8,000 more deaths
(Curwen M 1997)
Ratio of observed to expected deaths
Mortality and temperature distribution
Frequency
distribution of
max.
temperatures
1.5
1.25
1
Gradient represents
strength of low
temperaturemortality relationship
.75
0
10
20
Maximum daily temperature C
30
Excess Winter Deaths
LONDON, 1986-96
400
DAILY DEATHS
300
200
100
0
01jan1986
01jan1988
01jan1990
01jan1992
01jan1994
01jan1996
Inside vs Outside Cold
• Few older people live in homes without central
heating but many restrict their use of it mainly on
grounds of cost (fuel poverty)
• Moving from a cold home to outside cold carries
significantly more risk to health than moving from a
warm home
• Relatively minor cold exposures in daily life are
sufficient to induce significant hypertension and
haemoconcentration
• Linear inverse relationship between activity
levels and indoor cold with increased outdoor
excursions in older people living in cold homes
Relative risk of death
Inside Cold
1.6
Coldest 25% of homes
1.4
1.2
Warmest 25% of homes
1
.8
1Jan
1Apr
1Jul
Date
1Oct
31Dec
Euro-winter Study
Notable Findings
• Percentage increases in all cause mortality per 1C (below
18C) are greater in warm than in cold regions (eg Athens
vs south Finland)
• High indices of cold related mortality are associated with
– high mean winter temperatures
– low living room temperatures
– limited bedroom heating
– low clothing protection
– physical activity
• Lag effects exist between onset of cold and death
(4) What are its causes?
Causes of Winter Death
• Less than 1% due to hypothermia
• Small number of deaths due to influenza, except in
epidemic years (eg winter ‘89/90)
• Respiratory illness (eg COPD, bronchitis) 12 day’ lag
effect’; deaths declining due to warmer homes
• Thrombotic illness (eg MI, stroke) 3-7 day ‘lag effect’;
deaths show little change over time and are related to
outdoor cold exposure
(5) Can we do anything about it?
Aderdeen,Scotland
0-8°C in January
Yakutsk ,Siberia
-26.6°C
All cause mortality
unaffected
Kuwait
8-18°C in January
1950/1951
1952/1953
1954/1955
1956/1957
1958/1959
1960/1961
1962/1963
1964/1965
1966/1967
1968/1969
1970/1971
1972/1973
1974/1975
1976/1977
1978/1979
1980/1981
1982/1983
1984/1985
1986/1987
1988/1989
1990/1991
1992/1993
1994/1995
1996/1997
1998/1999
2000/2001
2002/2003
2004/2005
2006/2007
2008/2009
50 Year Regression Data
Excess Winter Mortality 1950 - 2010
120,000
100,000
80,000
60,000
40,000
20,000
0
Summary of the Evidence - Cold
• Extremes of cold incur high rates of morbidity and
mortality in older people via respiratory and
thrombotic illness
• Respiratory mortality appears to be falling due to
warmer homes
•Indoor and outdoor cold are independent risk factors
• Predisposing factors appear to be:
– age (frailty, co-morbidity)
– home conditions
– high-risk behaviour
– social isolation
– limited access to health and social care
– social inequality
Public Health Advice
“We will not be bullied into good health by the likes of Mr
Chadwick”
The London Times, 1848