Spatial Autocorrelation of Cancer Incidence in Saudi Arabia

Khalid Al-Ahmadi,Ali Al-Zahrani

doi:10.3390/ijerph10127207

Abstract

Little is known about the geographic distribution of common cancers in Saudi Arabia. We explored the spatial incidence patterns of common cancers in Saudi Arabia using spatial autocorrelation analyses, employing the global Moran’s I and Anselin’s local Moran’s I statistics to detect nonrandom incidence patterns. Global ordinary least squares (OLS) regression and local geographically-weighted regression (GWR) were applied to examine the spatial correlation of cancer incidences at the city level. Population-based records of cancers diagnosed between 1998 and 2004 were used. Male lung cancer and female breast cancer exhibited positive statistically significant global Moran’s I index values, indicating a tendency toward clustering. The Anselin’s local Moran’s I analyses revealed small significant clusters of lung cancer, prostate cancer and Hodgkin’s disease among males in the Eastern region and significant clusters of thyroid cancers in females in the Eastern and Riyadh regions. Additionally, both regression methods found significant associations among various cancers. For example, OLS and GWR revealed significant spatial associations among NHL, leukemia and Hodgkin’s disease (r² = 0.49–0.67 using OLS and r² = 0.52–0.68 using GWR) and between breast and prostate cancer (r² = 0.53 OLS and 0.57 GWR) in Saudi Arabian cities. These findings may help to generate etiologic hypotheses of cancer causation and identify spatial anomalies in cancer incidence in Saudi Arabia. Our findings should stimulate further research on the possible causes underlying these clusters and associations.

Highlights

Studies of the geographic variations in cancer mortality, prevalence and incidence have proven valuable for generating and evaluating etiologic hypotheses regarding cancer causation [1,2]
The purpose of this study was twofold: (i) to explore the spatial patterns and clusters of the most common cancers in Saudi Arabia using global and local spatial autocorrelation analyses and (ii) to examine whether the incidence rates of the most common cancers are spatially correlated at the city level using bivariate ordinary least squares (OLS) regression and geographically-weighted regression (GWR)
This study explored the spatial patterns and clusters of the most common cancers in Saudi Arabia using global and local spatial autocorrelation analyses

Summary

Introduction

Studies of the geographic variations in cancer mortality, prevalence and incidence have proven valuable for generating and evaluating etiologic hypotheses regarding cancer causation [1,2]. Rosenberg et al [5] examined the distribution of mortality from 40 cancers in Western Europe using spatial autocorrelation techniques. They found that cancer mortality rates were strongly spatially correlated, implying a similar spatial arrangement of the responsible agents. They concluded that local spatial autocorrelation is a useful technique for exploring epidemiological maps. The findings of that study showed a highly significant association among the incidence rates of pancreatic, lung and kidney cancers for both genders; less consistent correlations were found for colorectal, endometrial, ovarian and bladder cancers. Mandal et al [7] analyzed the correlation between female breast cancer and male prostate cancer in the United States between 2000 and 2005 using ordinary least squares regression (OLS) and geographically-weighted regression (GWR) analyses

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