Air temperature was associated with ambulance transports in Osaka area, Japan

doi:10.4236/health.2011.39092

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Vol.3, No.9, 545-548 (2011)

doi:10.4236/health.2011.39092

Health

Air temperature was associated with ambulance

transports in Osaka area, Japan

Nobuyuki Miyatake1*, Noriko Sakano1, Shoko Murakami1, Takeshi Suzue2, Takeshi Yoda2,

Akira Yoshioka2, Tomohiro Hirao2

1Department of Hygiene, Faculty of Medicine, Kagawa University, Kagawa, Japan;

*Corresponding Aut hor: [email protected]

2Department of Public Health, Faculty of Medicine, Kagawa University, Kagawa, Japan.

Received 4 July 2011; revised 1 August 2011; accepted 9 August 2011.

ABSTRACT

We investigated the link between ambulance

transports and meteorological parameters of

summer by using daily data in Osaka area, Ja-

pan. Daily observations for ambulance trans-

ports (from July 1 to September 30, 2009) were

obtained from Fire Department Service in Osaka.

Data of meteorological parameters in Osaka

area, Japan (from July 1 to September 30, 2009)

were also obtained from Japan Meteorological

Agency. Effect of meteorological parameters on

ambulance transports was analyzed. A total of

49,526 ambulance transports were observed

from July 1 to September 30, 2009 in Osaka,

Japan. Ambulance transports were significantly

correlated with mean air temperature (r = 0.298),

the highest air temperature (r = 0.347), the low-

est air temperature (r = 0.209) and daylight hour s

(r = 0.301). The higher air temperature was as-

sociated with higher ambulance transports of

summer in Osaka area, Japan.

Keywords: Ambulance Transports;

Air Temperature; Osaka Area; Daylight Hou rs

1. INTRODUCTION

Global warming has become public health challenge

in Japan. Global average temperatures are predicted to

increase between 1.4˚C and 5.8˚C by the end of this cen-

tury [1]. We have previously showed that estimated

changes in mean temperature was 1.6˚C for 50 years in

Osaka areas, Japan [2]. In addition, by using monthly

data, higher air temperature was associated with ambu-

lance transports in Takamatsu [3] and Okayama [4] areas,

Japan. Basu et al. also reported that th e relation between

elevated ambient air temperature and mortality in their

review [5]. However, the link between ambulance trans-

ports by using daily data and meteorological parameters

i.e. air temperature, humidity, atmospheric pressure and

daylight hours still remains to be investigated.

Therefore, we investigated the relationship between

ambulance transports of summer and meteorological

parameters by using daily data in Osaka area, Japan.

2. METHODS

2.1. Study Area

Osaka area is the second largest metropolitan area in

Japan and its population is abo ut 8.7 million . Osaka city

(2.6 million population, 220 km2) is located in the center

of the metropolitan area, and have been mostly urban-

ized for a long time in Japan. The Osaka plain is sur-

rounded by Hokusetsu and Rokko mountains to the north,

Ikoma mountain on the east side, Izumi Mountain in the

south, and Osaka Bay to the west.

2.2. Ambulance Dat a

Daily incidence data of ambulance transports was ob-

tained from Fire Department Service in Osaka from July

1 to September 30, 2009 [6].

2.3. Meteorological Parameters

Daily meteorological parameters in Osaka areas in

Japan for the required periods were obtained from Japan

Meteorological Agency [7]. The observation spots were

located at the central in the area. Daily meteorological

parameters i.e. mean atmospheric pressure (land surface)

(hPa), mean atmospheric pressure (sea surface) (hPa),

total precipitation (mm), mean air temperature (˚C), the

highest air temperature (˚C), the lowest air temperature

(˚C), mean humidity (%), the lowest humidity (%), mean

velocity of the wind (m/s) and daylight hours (hours)

N. Miyatake et al. / Health 3 (2011) 545-548

546

were used for analysis.

2.4. Statistical Analysis

Simple correlation analysis was used to test the sig-

nificance of the linear relationship among continuous

variables. p < 0.05 was considered to be statistically sig-

nificant.

3. RESULTS

Profiles of used daily data in Osaka area from July 1

to September 30, 2009 were summarized in Table 1. A

tota l of 49,526 ambul ance transports wer e observed from

July 1 to September 30, 2009 in Osaka area, Japan.

Mean ambulance transports was 538.3 ± 33.0/day, re-

spectively.

We investigated the relationship between ambulance

transports and meteorological parameters by simple cor-

relation analysis (Table 2). Ambulance transports were

significantly correlated with mean air temperature, the

highest air temperature (Figure 1), the lowest air tem-

perature and daylight hours. Correlation coefficient rate

Table 1. Profiles of used daily data in Osaka area from July 1 to September 30, 2009.

Mean ± SD Minimum Maximum

Number of days 92

Mean atmospheric pressure (land surface) (hPa) 1000.2 ± 4.3 990.0 1010.2

Mean atmospheric pressure (sea surface) (hPa) 1009.6 ± 4.4 999.3 1019.9

Total precipitation (mm ) 2.8 ± 5.9 0.0 30.5

Mean air temperature (˚C) 26.6 ± 2.3 20.8 30.8

The highest air temperature (˚C) 31.1 ± 2.8 22.0 36.3

The lowest air temperature (˚C) 23.3 ± 2.5 17.8 27.7

Mean humidity (%) 65.4 ± 9.2 48.0 88.0

The lowest humidity (%) 47.7 ± 11.4 27.0 81.0

Mean velocity of the wind (m/s) 2.4 ± 0.6 1.4 4.7

Daylight hours (hours) 5.6 ± 3.9 0.0 12.3

Ambulance transport (number/day) 538.3 ± 33.0 454.0 616.0

Table 2. Simple correlation analysis between ambulance transports and meteorological pa-

rameters from July 1 to September 30, 2009.

r p

Mean atmospheric pressure (land surface) (hPa) 0.086 0.4165

Mean atmospheric pressure (sea surface) (hPa) 0.090 0.3927

Total precipitation (mm ) –0.085 0.4186

Mean air temperature (˚C） 0.298 0.0039

The highest air temperature (˚C) 0.347 0.0007

The lowest air temperature (˚C) 0.209 0.0461

Mean humidity (%) –0.076 0.4694

The lowest humidity (%) –0.161 0.1250

Mean velocity of the wind (m/s) 0.152 0.1480

Daylight hours (hours) 0.301 0.0035

N. Miyatake et al. / Health 3 (2011) 545-548

547547

˚C

Figure 1. Simple correlation analy sis between ambulance transports (/day) and the highest air

temperature (˚C) by using da ily data in Osaka ar ea, Japa n.

between the highest air temperature and ambulance

transports was the highest. However, other parameters

were not correlated with ambulance transports.

4. DISCUSSION

We firstly evaluated the link between ambulance

transports and meteorological parameters by using daily

data in Osaka area, Japan. The highest air temperature

was closely associated with ambulance transports.

Average subsurface temperature profiles in four Asian

cities (Tokyo, Osaka, Seoul and Bangkok) were com-

pared and analyzed to evaluate the effects of surface

warming [8]. The magnitude of surface warming was the

largest in Tokyo (2.8˚C), followed by Seoul, Osaka and

Bangkok. The combination of the heat island effect due

to urbanization and global warming on subsurface tem-

peratures also relates to global ground water quality is-

sues [9]. In addition, in some literatures, the link be-

tween high temperatures and heat-related diseases has

been reported. Bai et al. reported that the number of un-

usual deaths in the summer of 1994 in Osaka, Japan was

more compared to those of previous years [10]. Nakai et

al. also investigated heat-related deaths in Japan from

1968 through 1994 and heat-related deaths were most

prone to occur on days with a peak daily temperature

above 38 degrees C [11]. Th ey reported that incidence of

heat-related deaths showed and exponential dependence

on the number of hot days [11]. Qiu et al. reported that

an unusually hot spell in 1999 was followed by a high

mortality rate in Hokkaido, Japan [12]. Piver et al.

showed that heat stroke was associated with prolonged

exposures to higher air temperatures that usually occur

in the summer months of July and August in 1980-1995

in Tokyo [13]. In our previous study, higher air tem-

perature was closely associated with higher ambulance

transports in Takamatsu and Okayama city using

monthly data [3,4]. We also found that high air tem-

perature was associated with ambulance transports by

using daily data in Osaka area, Jap an in this study. Coef-

ficient rate between ambulance transports and the high-

est air temperature was the highest among parameters.

Furthermore, the slope of the regression line (change in

highest air temperature vs change in ambulance trans-

ports) in Osaka city was 4.125 (Figure 1). Accordingly,

we found that a 1˚C increase in highest air temperature

of summer in Osaka area, Japan, corresponded to a

4.125/day increase in ambulance transports in Osaka

area, Japan.

Potential limitations still remain in this study. First,

the link between ambulance transports and air tempera-

tures, which was noted in this study, may not apply for

the link among individuals. Second, we could not di-

rectly evaluate heat-related diseases or deaths. Therefore,

we could not accurately evaluate the link between am-

bulance transports and high air temperatures. Further

studies are required to prove such link.

N. Miyatake et al. / Health 3 (2011) 545-548

548

5. ACKNOWLEDGEMENTS

This research was supported in part by Research Grants from FU-

KUTAKE Science & Culture Foundation, Japan.

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