Spatio-temporal analysis of colorectal cancer using a geographic information system in the Iranian military community during the period 2007–2016
Article in Journal of the Royal Army Medical Corps · February 2019
DOI: 10.1136/jramc-2018-001151
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Spatio-temporal analysis of colorectal cancer using a geographic information system in the Iranian military community during the period 2007–2016
Alireza Khoshdel,
1M Alimohammadi,
2M Sepandi,
3,4Y Alimohamadi,
2,5P Jalali,
5M Janani
5To cite: Khoshdel A, Alimohammadi M, Sepandi M, et al.
J R Army Med Corps Epub ahead of print: [please include Day Month Year].
doi:10.1136/
jramc-2018-001151
1Military Epidemiology Research Center, Aja University of Medical Sciences, Tehran, Iran
2Pars Advanced and Minimally Invasive Medical Manners Research Center, Pars Hospital, Iran University of Medical Sciences, Tehran, Iran
3Health Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
4Department of Epidemiology and Biostatistics, Faculty of Health, Baqiyatallah University of Medical Sciences, Tehran, Iran
5Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran Correspondence to Y Alimohamadi, Pars Advanced and Minimally Invasive Medical Manners Research Center, Pars Hospital - Iran University of Medical Sciences, Tehran 14496, Iran; y. alimohamadi67@ gmail.
com
Received 28 December 2018 Revised 28 January 2019 Accepted 30 January 2019
© Author(s) (or their employer(s)) 2019. No commercial re-use. See rights and permissions. Published by BMJ.
Key messages
► The incidence of colorectal cancer (CRC) has increased in the Iranian military community in recent years.
► The incidence of CRC is higher in men than in women.
► The incidence of CRC in the North of Iran is higher than in the South.
► Spatial clusters of CRC in the Iranian military community were observed in North and North West Iran.
AbsTrACT
Introduction Colorectal cancer (CRC) is one of the most prevalent cancers among Iranian people. The study of spatio-temporal distribution of disease has an impor- tant role in the design of disease prevention programmes.
The purpose of the current study was to describe the spatio-temporal distribution of CRC in the Iranian military community as a sample of the Iranian population.
Methods In the current ecological study, all registered cancer cases in the Iranian military community during the period 2007–2016 were considered. To identify hotspots, Getis-Ord Gi statistics were used. All analyses were performed using ArcGIS 10.5 and Excel 2010.
results The highest incidences of CRC in 2007–2008, 2009–2010 and 2011–2012 were recorded in Kerman- shah province. The highest incidences of CRC in 2013–
2014 were seen in Kermanshah, Ghilan, Tehran and North Khorasan. In 2007–2008 and 2009–2010, hotspots were detected in West Azarbayjan. In 2011–2012, hotspots were detected in Zanjan and Qazvin. In 2013–2014, a hotspot was detected in Qazvin. Finally, West Azerbaijan was the hotspot for CRC in 2015–2016.
Conclusions The incidence of CRC in men was higher than in women. Also it appeared that North and North West Iran were risk areas for this disease, and so these areas should be considered in the design of disease prevention programme for this cancer type. Additionally, the determination of individual risk factors in the afore- mentioned geographical areas can play an important role in the prevention of this type of cancer.
InTrOduCTIOn
Cancer is one of the most important causes of death worldwide and the third most prevelent cause of death in Iran after coronary heart disease and accidents.1 Among all types of cancers, colorectal cancer (CRC) is the second most common globally, with over 1 million new cases per year, of which about half of these cases result in death.2 In the Islamic Republic of Iran, CRC is the fourth most common cancer in men after gastric, prostate and bladder cancers with an adjusted standardised inci- dence rate of 7.8 per 100 000 and an adjusted stan- dardised mortality rate of 3.6 per 100 000.3 This type of cancer is the third most common cancer in Iranian women after breast and stomach cancers, with an age-adjusted incidence rate of 6.4 per 100 000 and an age-adjusted mortality rate of 4.4 per 100 000. Ooverall, CRC is the third most common cancer found in men and women after breast and
stomach cancers, and comprises 7% of the inci- dence rate and 7.6% of the mortality rate of all cancers.4 Compared with Western countries, there is a low incidence of CRC among elderly Iranians as well as a high incidence in young people, which is likely to lead to a substantial increase in the disease prevalence in the future.5 Distribution of CRC in the different regions of Iran is not uniform. The incidence rate varies up to 1.8-fold between prov- inces when comparing the highest and lowest rates.
The incidence rate ranges from 5.9 per 100 000 in Ardabil to 10.7 per 100 000 in Golestan province.6 According to reports, several risk factors such as poor diet, low physical activity, overweight, ciga- rette smoking, and alcohol consumption are asso- ciated with the incidence of CRC.7 In addition, a substantial number of place risk factors may play an important role in the incidence and mortality of this cancer type.8 9 Geographical location is an important factor in disease epidemiology, especially in relation to cancer, because risk factors can vary in different locations. Appropriate information on different types of cancers in specific geographical areas can be very helpful in planning health services for the treatment and screening of high-risk groups in those areas.10 Disease patterns, especially for different cancer types, can vary over time. CRC also has varying time-patterns in different coun- tries. In Iran, the increasing trend of incidence and mortality rate of CRC has been reported previ- ously.11–13 Over the past three decades, the lifestyle of Iranian people as a large population living in the Persian Gulf region has slowly changed to a Western lifestyle.14–16 Accordingly, even in low-risk areas, an increase in CRC incidence in the future is inevi- table.4 17–19 The military population may differ from the general population as regards factors such as
on 16 February 2019 by guest. Protected by copyright.http://jramc.bmj.com/
Figure 1 Trend of registered colorectal cancer cases in the Iranian military community during the period 2007–2016.
Figure 2 Incidence rate (per 100 000 individuals) of colorectal cancer in the Iranian military community by province during the - 2007–2016.
physical fitness, smoking, level of anxiety, alcohol consumption, diet, exposure to sunlight, access to medical care, and so on. In the United States, CRC has been shown to be less prevalent in the military population compared with the general population.20 21 Our research has identified few studies in the literature about the spatio-temporal distribution of CRC in the Iranian military community. Consequently, the aim of the current study was to conduct a temporal trend analysis of incidence rate, and also to identify regional spatial clusters of CRC in the Iranian mili- tary community using spatio-temporal analysis for the period 2007–2016.
MeThOds study area
Iran is a country in the Middle East with a total area of 1 648 195 km2. According to the last National Census in 2016, the total population of Iran is approximately 80 million. Iran has a common border with Armenia, Turkmenistan and Azerbaijan in the North; Afghanistan and Pakistan in the East; the Persian Gulf and Gulf of Oman in the South; and Iraq and Turkey in the West.
study design
In this ecological study all registered CRC cases during the period 2007–2016 in the Iranian military community were described and analysed.
data analysis Temporal analysis
Pearson correlation coefficient was used to assess the trend anal- ysis of the incidence of CRC during the period 2007–2016.
spatial analysis
A Choropleth map was used to describe the distribution of CRC cases (per 1 00 000 people) in the Iranian military community.
All analyses were performed using ArcGIS 10.5 and Excel 2010.
hotspot identification
Hotspot analysis was used to identify spatial clusters of disease.
Getis-Ord Gi statistics were used to identify hotspots. A high score on this index combined with a lower p-value indicates the clustering of CRC. The Gi statistics formula is as follows:
G∗i =
∑n
j=1Wi,jxj−X∑n
j=1Wi,j
S
��
��n
∑n j=1W2i,j−(∑n
j=1Wi,j)2
n−1
where Xj is the incidence of CRC for province j, wi.j is the spatial weight between provinces i and j, and n is the total number of provinces. X and S, are calculated as follows:
X =
∑n j=1xj
n
S =
∑n j=1x2j
n −(X)2
resulTs
The mean age of CRC cases in the current study was 66.42±12.31 years. Of the total cases, 938 (44.29%) were female and 1180 (55.71%) were male. A significant increasing trend of CRC in the Iranian military community from 2007 to 2016 was observed (p=0.01) (Figure 1). Considering the inci- dence rate during the study period, Kermanshah province had
the highest incidence rate (Figure 2). Regarding the distribution of CRC by province, the highest incidence rates of CRC in the periods 2007–2008, 2009–2010 and 2011–2012 were seen in Kermanshah province. The highest incidence rates of CRC in 2013–2014 were recorded in the following provinces: Kerman- shah, Ghilan, Tehran and North Khorasan. During 2015–2016, Mazandaran and Qom were the provinces with the highest inci- dence of CRC (Figure 3A–E). The CRC hotspots observed in the Iranian military community were as follows: 2007–2008, 2009–2010 – West Azarbayjan; 2011–2012 – Zanjan and Qazvin; 2013–2014 – Qazvin province; and 2015-2016 – West Azerbaijan (Figure 4A–E).
dIsCussIOn
The aim of the current study was to determine the spatio-tem- poral distribution of CRC in the Iranian military community.
Our results show that the mean age of patients in the current study was higher than in the Haj Manoochehri study in Qazvin, but lower than the mean age of CRC patients in Western coun- tries.22–25 The occurrence of colon cancer at a young age can lead to a severe decline in the patient's quality of life.26 27 Some 55.71% of the total cases in the current study were male. In a study carried out in the Iranian general population, the incidence of CRC in men was higher than in women.24 28 29 A survey that examined the gender distribution of the incidence and mortality rate of CRC in Asia found that the incidence of this cancer was higher in males than in females.30 Also in the United States, the on 16 February 2019 by guest. Protected by copyright.http://jramc.bmj.com/
Figure 3 Geographical distribution of incidence rate of colorectalcancer in the Iranian military community during the period 2007–2016.
incidence of CRC is higher in men than in females in the general population.31 All these results are compatible with those of the current study. The temporal trend of CRC in the Iranian military community from 2007 to 2013 increased with a mild slope but after 2013 some severe fluctuations in the pattern of reported cases were seen; however, despite the lack of any linear pattern, this increasing trend is still visible. A similar increasing trend was also reported in the general population.28 According to the time trend of reported cases, an increase in the incidence of CRC in the Iranian military population in the future is inevitable. Other studies have shown an increasing pattern of CRC mortality in Asian countries.30 This rising pattern was also observed in the Iranian general population.24 29 Based on a spatial model of the distribution of cases in a 2-year time interval, excluding five provinces (Yazd, Chaharmahal and Bakhtiari, Kohgiluyeh and Boyer Ahmad, Ilam and Ardabil) due to lack of data, Kerman- shah province had the highest number of reported cases of CRC (more than 200 cases per 100 000) of all the provinces. It would appear that the results of the present study are inconsistent with the distribution of CRC in the Iranian general population.6
During 2013–2014, the following provinces had the highest CRC incidence rates: Ghilan, Arak, Tehran and Khorasan Razavi (excluding Kermanshah). During 2015–2016, two other prov- inces (Qom and Mazandaran) were added to the list of high-inci- dence provinces. According to the pattern of CRC in the general population, the majority of cases were seen in the Central, Northern and Western provinces of Iran, which is consistent with the results of the current study.28 The incidence rate of CRC in Qom, Fars, East Azerbaijan, Golestan, North Khorasan, Hamadan and Lorestan was about 100 to 150 per 100 000 indi- viduals. Due to the increasing trend of CRC, it is expected that the incidence rate of this cancer in the Iranian military commu- nity in the aforementioned provinces will increase to more than 200 per 100 000 individuals in the future.
In order to apply appropriate interventions for the preven- tion of this cancer type, the main risk factors need to be deter- mined. Some factors such as socioeconomic status, access to screening care, diet, Western lifestyle, obesity, lack of mobility, and environmental factors may contribute to the increasing trend of CRC. Genetic factors should also be considered in the
on 16 February 2019 by guest. Protected by copyright.http://jramc.bmj.com/
Figure 4 Geographical distribution of colorectal cancer hotspots in the Iranian military community during the period 2007–2016.
CRC epidemiology.22 29 32–35 In a survey conducted on different ethnicities in the United States, the incidence trend of CRC was found to be decreasing in the general population, while in Native Americans the incidence showed an increasing trend over a 12-year period.31 This difference between different popula- tions may be due to genetic factors. Finally, a health education programme that focuses on the lifestyle and diet of at-risk popu- lations can be very beneficial in the prevention of this cancer type. According to the results of a recent study, diet modification is an effective measure in reducing the risk of CRC.36
COnClusIOns
The present study identified CRC hotspots in the years under investigation. North and North West Iran have the greatest clus- tering of CRC in the Iranian military community. Consequently, in designing cancer prevention programmes these geographical areas should be targeted by the Iranian military medical service.
Additionally, the Iranian military medical service and Aja Univer- sity of Medical Sciences should employ analytical studies to determine the factors that influence the incidence and preva- lence of CRC in the aforementioned geographical areas.
Contributors All the authors contributed to the study, AK: idea, data collection, data analysis. MA, MS, PJ, MJ: data analysis, manuscript preparation. YA: data collection, data analysis, manuscript preparation. All activities were supervised by YA.
Funding This study was funded by Aja University of Medical Sciences (Grant number IR.AJAUMS.REC.1395.27).
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; internally peer reviewed.
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