effects of the el nino phenomenon and ambient temperature on hospital admissions for diarrheal...
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Effects of the El Nino phenomenon and ambient temperature on hospital admissions for diarrheal disease
The Lancet Feb. 5, 2000
William Checkley, Leonardo Epstein, Robert H Gilman, Dante Figueroa, Rosa I Cama,
Jonathan Patz, & Robert E Black
What is El Niño?
West trade winds keep the warm waters of the central Pacific Ocean in place
Normal conditions
El Niño conditions
West trade winds weaken and the warm waters of the central Pacific Ocean move towards the equatorial Pacific until they reach the South American coast
• El Niño is associated with dengue, malaria, and cholera.
• Now, researchers have found that El Niño increases hospital admissions for diarrheal disease by 200%.
Public Health Significance I
• Researchers estimate that diarrheal disease admissions increased by more than 8% with every 1 degree C. rise in temperature;
• There could be an increase of cases in the millions in diarrheal disease cases worldwide with each degree of increase in ambient temperature due to global warming.
Public Health Significance II
• Whether the 1997-1998 El Niño episode had an effect on hospital admissions for diarrheal disease.
• The relationship between weather variability and diarrheal diseases.
The study examined
• Daily admissions to the Oral Rehydration Unit (ORU) of the Instituto Nacional del Niño, Lima, Peru – from January 1,1993 to Nov 15, 1998.
• Over 57,000 diarrheal admissions during the study period.
• Information on each child at the time of admission included: age (all children < 10), weight and height (nutritional status), and severity status.
Methods
• Daily mean ambient temperature and relative humidity in Lima (Jan 1993 to Nov 1998) obtained from SENAMHI.
• Definitions: El Niño period as January 1, 1997 to August 31, 1998. Extension of the global ENSO definition to account for local differences in weather.
Methods
Dia
r rhe
al a
dmis
s ion
s
20
40
60
Tem
pera
tur e
(C
els i
us)
16
18
20
22
24
26
Rel
ativ
e H
umi d
ity (
%)
60
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90
1993 1994 1995 1996 1997 1998J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N
1993 1994 1995 1996 1997 1998
Age
at a
d mis
s sio
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onth
s )
+ + ++
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1015
2025
3 03 5
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for-
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-1.0
-0.5
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0 .5
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rag e
he i
g ht-
for-
age
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0 .2
J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N
Monthly measurements
El Niño period
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+ Observed admissions
++
Expected admissions had El Niño not occurred
Onset of El Niño
b(t) =
k Nk (t - 1461)+
k = 1
r + 1
a(t) =
0 ++
i sini = 1
n
j cos
j = 1
m
2 fi t
1461(
2 gj t
1461(
i.e., b(t) is zero until the onset of El Niño
Expected admissions had El Niño not occurred
Expected (estimated) admissions during the El Niño
•Loss of periodic, pre-El Niño pattern and significant increase above normal during El Niño (p < 0.001);
•Observed temperature was consistently higher than normal. On several days it was > 5 oC above normal;
•Decline in excess temperature began around June 1998; lower than normal by September 1998.
RESULTS
Effects of El Niño on ambient temperature in Lima
Am
bie
nt
Tem
pe
rat u
r e
( Ce
lsi u
s)1
41
61
82
02
22
42
62
8
Daily measurements
Ob
ser v
ed
- E
xpe
cte
d
Tem
pe
rat u
re
-20
24
6
J F M A M J J A S O N D J F M A M J J A S O N1997 1998
Expected + Observed
During El Niño, diarrheal admissions also lost their periodic, pre-El Niño pattern and increased significantly above normal (p < 0.001);
Observed admissions were uniformly larger than expected. In the winter, daily admissions increased up to 200 percent above expected;
6,225 admissions were attributable to El Niño and cost the ORU $ 277,000.
RESULTS
Effects of El Niño on ambient temperature in Lima
Dai
ly a
dmis
sion
s f o
r di
arrh
ea0
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Daily measurements
Rel
ativ
e r is
k of
dia
r rhe
al
adm
issi
ons
duri n
g E
l Ni ñ
o0 .
51 .
01 .
52 .
02 .
5
J1997
F M A M J J A S O N D J1998
F M A M J J A S
Expected + Observed
Daily measurements
Dai
ly a
d mi s
s io n
s fo
r d i
a rrh
e a
020
4060
O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N
1996 19981997
Expected admissions assuming no El Niño effect
Expected admissions during El Niño
TO
TE
log
pre-El Niño period El Niño period
-0.2 -0.1 0.0 0.1 0.2 0.3
-1.5
-1.0
-0.5
0 .0
0 .5
1 .0
1 .5
-0.2 -0.1 0.0 0.1 0.2 0.3
CO
CE
log = excess increase in admissionsTO
TE
log = excess increase in temperature
CO
CE
log
• El Nino increased diarrheal admissions, especially during the winter when admissions increased by 200 percent;
• An increase of 8% in admissions per 1 degree C increase suggests that global warming is likely to have a strong effect on diarrheal diseases – increasing cases by millions worldwide per degree temperature increase, and
• Early warning of future El Nino episodes can help us better treat and prevent cases of diarrheal illness.
Key Points