Document Type : Commentary
Authors
1 MD, PhD, Department of Radiation Oncology, Edward Hines Jr VA Hospital, Hines, IL 60141, United States
2 MD, PhD, Department of Radiation Oncology, Loyola University Stritch School of Medicine, Chicago, United States
3 PhD, Bevelacqua Resources, Richland, Washington 99352, United States
4 PhD, Medical Physics Department of, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
5 PhD, Department of Diagnostic Imaging, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, United States
Abstract
It has recently been reported that differences in life expectancy can be linked to income. In Norway, a registry-based study that included all Norwegian residents aged ≥ 40 years (2005-2015) was performed. This study showed substantial and increasing gaps in life expectancy by income level during the interval between 2005-2015. Compared to the United States, the largest life expectancy differences were for individuals in the lower to middle part of the income distribution, although differences were observed at all income levels. Despite its undeniable strengths and although this paper can be considered as a significant contribution to this field, it has some shortcomings. The first shortcoming of this study is due to ignoring the effects of population exposures to natural and man-made ionizing and non-ionizing radiation on life expectancy. Another shortcoming arises from ignoring the strong impact of education on lifestyle. In summary, what is observed in this study might be at least to some extent, due to education-related changes in lifestyle and not necessarily income (despite the mutual links between education and income).
Keywords
Introduction
To discern the differences in life expectancy and causes of death in Norway that can be linked to income and to compare those differences with current US estimates, Kinge et al., [ 1 ] have previously performed a registry-based study that included all Norwegian residents aged ≥ 40 years (2005-2015). The authors observed substantial and increasing gaps in life expectancy by income level during the interval between 2005-2015. Compared to the United States, the largest life expectancy differences were for individuals in the lower to middle part of the income distribution, although differences were observed at all income levels. Despite its undeniable strengths and although this paper can be considered as a significant contribution to this field, it has some shortcomings.
The first shortcoming of this study is due to ignoring the effect of population exposures to natural and man-made ionizing and non-ionizing radiation on life expectancy. Due to the orientation of the Earth’s geomagnetic field, primary and secondary cosmic rays (energetic charged particles from galactic and solar sources along with secondary radiation generated from impacts of these particles with our atmosphere) penetrate to much lower altitudes in the polar regions in countries including Norway. The routine observation of the northern lights (aurora borealis) in countries such as Norway and aurora australis or southern lights near the South Pole is explained by this phenomenon. Moreover, it has been reported that Norway is one of the most radon-rich European countries [ 2 ]. In addition, according to the Norwegian Radiation Protection Authority (Strålevern Rapport 2015:13) while Norway performs slightly fewer radiological examinations per person than the European average, it is among the European countries performing the most CT examinations. This report also states that due to high numbers of CT scans, Norway is among the European countries with the highest radiation doses from radiological examinations [ 3 ]. It is worth noting that some evidence shows that compared to non-irradiated individuals, exposure to low-dose radiation may increase lifespan and reduce cancer mortality [ 4 ]. The present study is not inconsistent with this assertion.
Another shortcoming arises from ignoring the strong impact of education on lifestyle [ 5 ].
It is well documented that higher levels of education induces individuals to exercise regularly and get regular health checkups [ 6 ]. Given this consideration, what is observed in this study might be at least to some extent, due to education-related changes in lifestyle and not necessarily income (despite the mutual links between education and income).
Authors’ Contribution
All authors have made substantial contributions to conception and design of the study and the review of the original Norway registry-based study. All authors have given final approval of the current version of the paper.
Conflict of Interest
None
References
- Kinge JM, Modalsli JH, Overland S, Gjessing HK, Tollanes MC, Knudsen AK, et al. Association of Household Income With Life Expectancy and Cause-Specific Mortality in Norway, 2005-2015. JAMA. 2019; 321:1916-25. Publisher Full Text | DOI | PubMed
- Strand T, Jensen CL, Ånestad K, Ruden L, Ramberg GB. High radon areas in Norway. International Congress Series. 2005; 1276:212-4. DOI
- Komperød M, Friberg EG, Rudjord AL. Radiation Doses to the Norwegian Population, Summary of radiation doses from planned exposure and the environment. Norwegian Radiation Protection Authority: Strålevern Rapport; Norway; 2015.
- Sutou S. Low-dose radiation from A-bombs elongated lifespan and reduced cancer mortality relative to un-irradiated individuals. Genes Environ. 2018; 40(1):1-14. Publisher Full Text | DOI | PubMed
- Stelmach W, Kaczmarczyk-Chalas K, Bielecki W, Drygas W. The impact of income, education and health on lifestyle in a large urban population of Poland (Cindi programme). Int J Occup Med Environ Health. 2004; 17:393-401. PubMed
- Park C, Kang C. Does education induce healthy lifestyle?. J Health Econ. 2008; 27:1516-31. DOI | PubMed
)