The Epidemiological Transition: A shift from Communicable to Non-communicable Disease

The Epidemiological Transition: A shift from Communicable to Non-communicable Disease
Paige M. Breedon and Austin A. Mardon

Despite the current COVID-19 pandemic, humankind is on the cusp of transitioning from being primarily inflicted by acute communicable diseases to being burdened by non-communicable chronic diseases. This transition, termed an epidemiological transition, is related to the rise of industrialization, advances in medicine and technology, changes in socioeconomic patterns, and the development of infrastructure that supports more sedentary and unhealthy lifestyles [3]. In general, this transition is due to many factors that all interrelate at some level, thus making it difficult to stop this chain reaction from derailing societies' health, economy, and ultimately the future of humankind. This epidemiological transition is much more evident for Western civilization but has started to sweep across the world as developing countries gain socioeconomic traction [3]. Thus, it is of concern for all individuals and needs to be recognized and addressed soon to ensure the future of the human race.

Factors Leading to the Epidemiological Transition
Rise of Industrialization
Firstly, industrialization, specifically the wide-scale development of the fast-food industry, has become a hallmark of Western civilization leading to countless problems for the health and wellbeing of the average consumer. In the beginning, fast food was an occasional venture for those fortunate enough to afford it, and now it has become an everyday must-have stop. Specifically, the industrialization of food in the United States has enabled affordable and easily accessible fast food that easily beats any healthy alternative [2]. Ironically, the transition has been from food insecurity to too much food access and consumption for many developed countries. Through advances in the agricultural industry (i.e. through the use of synthetic fertilizers, antibiotics in animal feed, and the rise of factory farming), fast food has become more accessible than healthier counterpart food companies [2]. In the United States alone, individual caloric intake has risen by 500 calories per day from 1970 to 2016 [2]. This substantial rise in caloric intake could be due to the food that is accessible being of little nutritional value, thus forcing individuals to indulge further, as well as the many chemicals, excess sodium, and fat found within the average disproportionately served fast food staple item. 
Understandably, the United States is also experiencing an obesity epidemic where levels of obesity are exceeding previously expected levels. Obesity, a multifactorial disease, substantially raises one's risks of morbidity, mortality, and being inflicted by countless other diseases. Therefore, not only does obesity individually impact one's quality and quantity of life, but it also has significant impacts on countries' health care systems. For instance, in 2015, the estimated annual healthcare costs attributed to obesity were USD 190 billion per year, exceeding the health care expenditures allocated in the United States by approximately 21% [1]. Therefore, it is of utmost importance to understand the epidemiology of chronic diseases such as obesity and address these problems before society's health deteriorates. 

Advances in Medicine and Technology
Another argument for why humankind has seen such an epidemiological transition could be due to advances in medicine and technology. As countries develop, they gain access to better health care and life-saving medicine, thus eliminating previously fatal communicable diseases. However, such medicine and health care seem to have less impact on diseases primarily due to lifestyle choices. Although individuals can have a genetic predisposition to certain chronic diseases, most non-communicable chronic diseases exist on the environmental side of the line of disease causation. Therefore, to observe changes in chronic disease trends, prevention programs need to be launched that target modifiable risk factors (i.e. lifestyle factors).

Socioeconomic Culture
A meta-analysis conducted by Zeng et al. (2018) attempted to examine the association between socioeconomic status and the incidence and progression of chronic kidney disease. The analysis found that chronic kidney disease prevalence was associated with socioeconomic status, specifically lower income and lower education [6]. Also, lower levels of income, occupation and combined socioeconomic status were significantly associated with progression to end-stage renal disease. This analysis demonstrates that socioeconomic status can affect the prevalence and progression of a disease [6]. Perhaps this association's mechanism is due to the relatively inexpensive and accessible nature of fast food that lower-income people can afford, the lack of physical activity and information, and healthcare quality. 

Built Environment
Furthermore, a study by Owen et al. (2018) intended to examine the associations of neighbourhood environment attributes with adults' objectively assessed sedentary time found that those living in areas with higher connectivity or better aesthetic had less sedentary time. Owen et al. 's (2018) findings supported other studies that demonstrated the association between street connectivity and aesthetics with levels of recreational walking. Both connectivity and aesthetics are examples of communal infrastructure affecting one's sedentary behaviour.

Rise of Urbanization
More generally, urbanization, which is on the rise in even developing countries, has both positive and negative effects on public health as it allows for better housing and access to food but can also result in infrastructure that inhibits a healthy, active lifestyle. For instance, Pinchoff et al. (2020) overlaid data from a 2010 Tanzania Demographic and Health Survey with a satellite-derived measure of built environment found a strong positive correlation between a measure of chronic inflammation predictive of cardiovascular disease, body mass index and the built environment. The correlation reflects the potentially adverse effects of urbanity on chronic disease markers, which has the potential to be harmful to public health even in less developed countries such as Tanzania [5]. As countries and cities are becoming more urbanized, their environment may be associated with more sedentary and stressful lifestyles as well as the consumption of fast food that is less nutritious.     

Amidst the epidemiological transition from communicable to non-communicable diseases, much has to be done to protect individuals, economies, and humankind as a whole in order to alleviate the burden of chronic disease. It is a shared responsibility for individuals, communities, and corporations to institute changes to improve public health, i.e. at the individual level, by practicing a healthy lifestyle, on the communal level by increasing accessibility and building communities to facilitate active transport. Although the problem of chronic disease does reflect some progress in society, this progress comes with a whole new realm of concerns for public health, which must be addressed to ensure a healthier tomorrow. 

REFERENCES
[1]     Hruby, A., & Hu, F. B. (2014). The Epidemiology of Obesity: A Big Picture.PharmacoEconomics, 33(7), 673–689. https://doi.org/10.1007/s40273-014-0243-x
[2]     Kramer, H. (2016). Kidney Disease and the Westernization and Industrialization of Food. American Journal of Kidney Diseases, 70(1), 111–121. https://doi.org/10.1053/j.ajkd.2016.11.012
[3]     Omran, A. R. (2005). The Epidemiologic Transition: A Theory of the Epidemiology of Population Change. The Milbank Quarterly, 83(4), 731–757.
https://doi.org/10.1111/j.1468-0009.2005.00398.x
[4]     Owen, N., Sugiyama, T., Koohsari, M. J., De Bourdeaudhuij, I., Hadgraft, N., Oyeyemi,
A., … Cerin, E. (2018). Associations of neighborhood environmental attributes
with adults’ objectively-assessed sedentary time: IPEN adult multi-country study. Preventive Medicine, 115, 126–133. https://doi.org/10.1016/j.ypmed.2018.08.023
[5]     Pinchoff, J., Mills, C. W., & Balk, D. (2020). Urbanization and health: The effects of the
built environment on chronic disease risk factors among women in Tanzania. PloS One, 15(11), e0241810–e0241810. https://doi.org/10.1371/journal.pone.0241810
[6]     Zeng, X., Liu, J., Tao, S., Hong, H. G., Li, Y., & Fu, P. (2018).        Associations between]
socioeconomic status and chronic kidney disease: a meta-analysis. Journal of
Epidemiology and Community Health (1979), 72(4), 270–279. https://doi.org/10.1136/jech-2017-209815

About the Authors
Paige Breedon is a second-year medical sciences undergraduate student at the University of Western Ontario with an interest in epidemiology, public health, and the biological sciences.
Dr. Austin Mardon is a geographer, author, researcher, assistant adjunct professor at the University of Alberta and the founder and director of the Antarctic Institute of Canada.