P96
THE INFLUENCE OF WEATHER ON HOSPITAL ADMISSION RATES FOR ACUTE
KIDNEY INJURY AND URINE TRACT INFECTION
Darren Green1,2, Philip A Kalra1,2, James P Ritchie1,2
1
Institute of Population Health, University of Manchester, UK
2
Salford Royal Hospital, Manchester Academic Health Sciences Centre, UK
AIM: It is established that seasonal climate variation, particularly that of winter, is associated
with variation in hospital admission rates for respiratory and cardiovascular diseases. We
hypothesised that, in the case of renal tract illnesses, there would be higher rates of acute
admissions during hot or humid weather than during cold spells based on an assumed
association between higher temperatures and dehydration.
METHODS: The study included all non-elective adult acute medical admissions to a single
acute Trust (catchment area 220,000) that had a coded primary diagnosis of urinary tract
infection (UTI) or acute kidney injury (AKI) and occurred between 1st April 2012 and 31st
March 2013. AKI was defined as an acute elevation in serum creatinine being the main reason
for admission, not by a specified absolute or minimum percentage rise. AKI were excluded if
secondary to another acute illness such as sepsis. Concurrent weather data were collected from a
Meteorological Station 6.7 miles from the hospital. Weather data collected were temperature,
depth of rainfall, humidity, sea-level air pressure, and wind speed.
The end points were total admissions per day for each of AKI and UTI. Association of each
weather factor with number of admissions was made by multivariate linear regression analysis
including the mean value of all recorded weather parameters over the preceding 7 days.
RESULTS:
There were 193 AKI admissions (median admissions per day = 1, range 0 – 4)
and 704 UTI admissions (median per day = 3, range 0 – 10) over 365 days. Patients were aged
64±20 years, 45% of AKI admissions were male, and 39% of UTI were male). The 7 day mean
values for each weather parameter were: temperature 8.8 ± 5.1 oC; relative humidity 82.0 ± 7.9
%; sea level pressure 1010 ± 10 kPa; rainfall 17.2 ± 15.3 mm; wind speed 12.6 ± 5.9 km/hr.
On multivariate analysis there was a significant inverse association between temperature and the
number of both AKI and UTI admissions per day. There was a significant association between
humidity and AKI. No other weather parameters were significant. These data are summarised in
table 1.
Table 1. The multivariate association of weather with acute hospital admissions for AKI
and UTI.
UTI
AKI
β
SE
Sig.
β
SE
Sig.
o
Temperature ( C)
-0.249
0.019
<0.001
-0.129
0.010
0.018
Relative humidity (%)
-0.030
0.013
0.687
0.184
0.013
0.002
Sea-level air pressure (hPa)
0.000
0.011
0.997
0.086
0.007
0.171
Depth of rainfall (mm)
0.031
0.025
0.598
-0.067
0.006
0.261
Wind speed (km/hr)
0.033
0.018
0.574
0.050
0.009
0.400
When considered together, UTI and AKI admissions accounted for 3,927 days of bed
occupancy at this acute Trust. In the summer, there were 865 days of bed occupancy compared
to 1,247 days in the winter. This equates to a seasonal difference of 30 extra days of bed
occupancy per week in the winter.
CONCLUSION:
Contrary to the hypothesis, both UTI and AKI admissions were more
common in colder weather. The seasonal difference in admissions and bed occupancy is too
small to require pre-emptive winter strategic planning for these illnesses alone but indicate that
increases in acute renal tract disease contribute to winter bed pressures.