Higher Temperatures Were Closely Associated with Higher Ambulance Transports in Takamatsu Area, Japan

doi:10.4236/jep.2011.21007

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Journal of Environmental Protection, 2011, 2, 72-75

doi:10.4236/jep.2011.21007 Published Online March 2011 (http://www.SciRP.org/journal/jep)

Higher Temperatures Were Closely Associated

with Higher Ambulance Transports in Takamatsu

Area, Japan

Nobuyuki Miyatake1, Masaki Nakao2, Noriko Sakano1, Shigeru Suna3, Takeshi Suzue4,

Tomohiro Hirao4

1Department of Hygiene, Faculty of Medicine, Kagawa University, Miki, Kagawa, Japan; 2Graduate School of Engineering, Osaka

City University, Osaka, Japan; 3Kagawa Prefectural College of Health Sciences, Japan; 4Department of Public Health, Faculty of

Medicine, Kagawa University, Miki, Kagawa, Japan.

Email: [email protected]

Received October 22nd, 2010; revised December 9th, 2010; accepted January 17th, 2011.

ABSTRACT

The link between high temperatures and ambulance transports in Takamatsu area, Japan was investigated. Monthly

observations for ambulance transports (2004-2008) were obtained from Fire Department Service in Takamatsu. Data

of temperatures in Takamatsu area, Japan (2004-2008) were used by Japan Meteorological Agency. Effect of high

temperatures on ambulance transports was analyzed. By using data from July to September, there were not clear dif-

ferences of mean temperatures and ambulance transports among years. Ambulance transports were significantly cor-

related with parameters of temperatures. Correlation coefficient rate between ambulance transports and the mean

temperature of maximum temperatures in a month was highest among parameters (r = 0.738, p = 0.0017). In add ition,

ambulance transports were also significantly correlated with the number of days over the level of 32˚C in a month (r =

0.782, p = 0.0006). Higher temperatures were closely associated with higher ambulance transports in Takamatsu area,

Japan.

Keywords: Te mperature, Ambulance Transports, Takamatsu Area, Fire Department Service in Takamatsu, Japan

Meteorological Agency

1. Introduction

Global average temperatures are projected to increase

between 1.4 and 5.8˚C by the end of this century [1]. On

local and regional scales, changes in land cover can

sometimes exacerbate the effect of greenhouse-gas-in-

duced warming, or even exert the largest impact on cli-

matic conditions. Most cities show a large heat island

effect, registering 5-11˚C warmer than surrounding rural

areas [2]. An increase in mortality related to heat waves

has been reported from various industrialized countries

[3-5].

The number of patients with heat stroke is surveyed by

National Institute for Environmental Studies in several

cities, except Takamatsu area, in Japan [6]. An increase

in summer temperatures is likely to increase the number

of patients with high temperatures related diseases.

Therefore, it is timely to assess local evidence of acute

health effects of high temperatures in Takamatsu area,

Japan.

In this study, to address this issue, we investigated

monthly ambulance use and its relation to high tempera-

tures in 5 summers in Takamatsu area, Japan.

2. Methods

2.1. Study Area

Takamatsu area, Kagawa prefecture, Japan, which in-

cludes Takamatsu city, Miki-cho and Ayagawa-cho, is on

the northern shor e of Shikoku Is land ( in a temperate zo n e

area). The populatio n of Kagawa prefecture is 1 000 000

and 470 000 people are situated on the Takamatsu area.

Currently several public offices of Shikoku district are

located in Takamatsu city. Although the surrounds of

Takamatsu had been used primarily as paddy fields for

agriculture, recently they have undergone rapid changes,

developing into residential and/or commercial areas. The

area’s emergency medical services are managed by Fire

Higher Temperatures Were Closely Associated with Higher Ambulance Transports in Takamatsu Area, Japan73

Department Service in Takamatsu and 14 ambulances

were in use in 2008 [7].

2.2. Ambulance Data

Monthly incidence data of ambulance transports was

obtained from Fire Department Service in Takamatsu

from July to September for 5 years (2004-2008) [7]. We

excluded the number of other ambulance transports i.e.

traffic accidents, fire accidents and injuries, and the

number of ambulance transports (per a month per ten

thousand persons) by acute diseases [8] was used for

analysis.

2.3. Temperatures

Daily and monthly temperatures in Takamatsu area, Ja-

pan for the required periods were obtained from Taka-

matsu Local Meteorological Observatory, Japan Mete-

orological Agency [9]. Mean temperature in a month,

mea n tempe ratur e of maxi mum temperatures in a month,

mean temperature of minimum temperatures in a month,

maximum temperature in a month, minimum temperature

in a month and the number of days over the level of var-

ious temperatures in a month were used for analysis.

2.4. Statistical Analysis

Simple correlation analysis was used to test the signifi-

cance of the linear relationship among continuous vari-

ables: p < 0.05 was considered to be statistically signifi-

cant.

3. Results

Changes in mean temperature in a month are summarized

in Figure 1. There were not clear differences of mean

temperature in a month for 5 years. There were not also

clear differences of ambulance transports (per a month

per ten thousand persons) for 5 years (Figure 2).

We investigate the relationship between ambulance

transports and parameters of temperatures from July to

September for 5 years (2004-2008) in Takamatsu area,

Japan (Table 1). Ambulance transports were signifi-

cantly correlated with parameters of temperatures. Cor-

relation coefficient rate between ambulance transports

and mean temperature of maximum temperatures in a

month was highest among parameters (r = 0.738, p =

0.0017). The slope of the regression line (changes in

mean temperature of maximum temperatures in a month

vs changes in ambulance transports) was 0.597 (Figure

3). Accordingly, we found that a 1˚C in mean tempera-

ture of maximum temperatures in a month corresponded

to a 0.597 increase in ambulance transports (per a month

per ten thousand persons) in Takamatsu area.

In addition, the relation between ambulance transports

and the number of days of over the level of various tem-

Table 1. Simple correlation analysis between ambulance

transports and parameters of temperatures in Takamatsu

area, Japan.

r p

Mean temperature in a month 0.7280.0021

Mean tem perat ure of m axim um tem per at ures i n a m ont h 0.7380.0017

Mean tem perat ure of m inim um tem per at ures i n a m ont h 0.6680.0065

maximum temperature in a month 0.6930.0042

minimum temperature in a month 0.5550.0318

Figure 1. Changes in mean temperature (2004-2008).

Figure 2. Changes in ambulance transports (2004-2008)

(per a month per ten thousand persons).

Figure 3. Simple correlation analysis between ambulance

transports and mean temperature in a month.

Higher Temperatures Were Closely Associated with Higher Ambulance Transports in Takamatsu Area, Japan

peratures was also evaluated (Table 2). Ambulance

transports were significantly correlated with the number

of days of over the level of various temperatures, espe-

cially over the level of 32˚C (r = 0.782, p = 0.0006)

(Figure 4).

4. Discussion

We firstly investigated the link between ambulance tran-

sports and parameters of temperatures in Takamatsu area,

Japan. Ambulance transports were significantly associ-

ated with high temperatures.

In some literatures, the relation between high tem-

peratures and heat stroke in Japan [10-12]. Nakai et al.

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

[10]. In addition, they reported that incidence of heat-

related deaths showed and exponential dependence on

the number of hot days [10]. Qui et al. reported that an

unusually hot spell in 1999 was followed by a high mor-

tality rate in Hokkaido , Japan [11]. Bai et al. also showed

that the number of un usual deaths in the summer of 1994

in Osaka, Japan was more compared to those of previous

years [12]. The human body dissipates heat in four ways:

convection, conduction, radiation and water evaporation.

When the temperature of the surrounding environment is

higher than the body temperature, water evaporation is

the only way in which the body can dissipate heat. When

the air temperature is over 34 degrees, cardiovascular and

nervous disorders can occur as a result of problems asso-

ciated with body temperature adjustment and metabolism

of water and salts [11]. Unexpectedly high temperatures

are particularly difficult for the elderly [13,14], and

chronic diseases [15]. In this study, we investigated the

relationship between ambulance transports and parame-

ters of temperatures, and close relationship was noted

between ambulance transports and high temperatures in

Takamatsu area, Japan. Although, we could not directly

evaluate the heat-related diseases or deaths, it seems

reasonable to suggest that simply dealing with high tem-

peratures in summer in Takamatsu city i.e. inno vation of

the thermal energy metabolism in cities and individual

coping with high temperatures might result in the ame-

lioration of ambulance transports in Takamatsu area,

Japan.

Potential limitation s still remain in this study. First, the

link between ambulance transports and temperatures,

which was noted in th is study, may not apply for the link

among individuals. Second, we could not directly evalu-

ate heat-related diseases or deaths. Third, daily data of

ambulance transports could not obtained in this study.

Therefore, we could not accurately evaluate the link be-

tween ambulance transports and high temperatures. Fur-

Table 2. Simple correlation analysis between ambulance

transports and number of days over the level of various

temperatures in a month.

r p

Number of days over 30˚C 0.682

0.0051

Number of days over 31˚C 0.778

0.0006

Number of days over 32˚C 0.782

0.0006

Number of days over 33˚C 0.723

0.0023

Number of days over 34˚C 0.677

0.0056

Number of days over 35˚C 0.644

0.0006

Figure 4. Simple correlation analysis between ambulance

transports and the number of days over the level of various

temperatures.

ther studies are required to prove such link.

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