By Chloe Teng
Non-communicable diseases (NCDs), otherwise known as chronic diseases, collectively refer to disorders that are not directly transmissible from one individual to another, such as cardiovascular diseases, cancers, and diabetes. These conditions, which are often long-term, are commonly a result of multiple factors, ranging from genetic, behavioural, to environmental. NCDs currently account for a shocking 71% of all deaths globally and pose a significant threat to low- and middle-income countries due to their demographic and socioeconomic transitions (WHO, 2018). Links between NCDs and infectious pathogen risk factors have also previously been investigated and established. For example, data has shown an emergence of novel aetiological factors leading to NCDs, such as Helicobacter pylori as a risk for gastric cancer (Wroblewski et al., 2010). Even so, the quantifiable global burden of NCDs due to infectious causes has yet to be attempted. The study carried out by Coates et al. (2020) further challenges the notion of NCDs only being attributable to non-infectious causes, and comprehensively quantifies the global burden of NCDs from infectious risk factors.
Firstly, the disability adjusted life years (DALYs) from NCDs attributable to infectious causes defined by the Global Burden of Disease Study of 2017 were identified. It was found that approximately 130 million DALYs, which was 8.4% of the global NCD DALYs could be accounted for by NCD burdens attributable to infection (Coates et al., 2020). DALYs is a measure of disease burden, representing the number of years lost due to disabilities or early death. This indicated that a substantial proportion of global NCD disease burden was due to infectious causes. Interestingly, the proportion of infection-related NCD burden varied across regions and demographics, with the greatest rates being in low- and middle-income regions such as Sub-Saharan Africa, Oceania, parts of Latin America, South, and Southeast Asia (Coates et al., 2020). In comparison, the rates were lowest in Australia and New Zealand, amongst other high-income regions. Results as such clearly highlight the disproportionate burden of NCDs from infectious causes. Certain geographical regions even showed specific increased importance of infectious risks in NCD cases, such as the burden of cervical cancer caused by HPV in Sub-Saharan Africa. Each region therefore displayed varying levels of infectious attributable NCD burden, and for which the precise infectious risks and NCDs differed accordingly as well.
In Sub-Saharan Africa, infectious conditions were determined to account for a larger estimated proportion of NCD burden than common risk factors such as dietary risks, tobacco use, and alcohol use (Coates et al., 2020). Although the young population age would have contributed to the high relative rate of infectious risk factors compared to other regions, this remains a result worth further investigation. The data obtained challenges the perception that NCDs are typically caused by four modifiable risk factors – tobacco use, harmful alcohol use, unhealthy dietary options, and lack of physical activity (NCDAlliance, 2020). Instead, it appears that infectious risk factors have overcome three of the four main factors in importance for this population.
In a global context, the 8.4% crude proportion of NCD burden due to infectious causes appeared higher than other risk factors such as air pollution and the aforementioned alcohol use by 1.7% and 3.9%, respectively. Factors such dietary risks and tobacco use, however, remained more prevalent (Coates et al., 2020). What this information and the region-specific data seem to suggest is that infectious causes need to be considered a substantial target for NCD prevention efforts, and the strategy for which must also be tailored to each population’s own burdens and needs.
Despite the results obtained from this study, further research is still required to conclusively determine the risks and burden of infectious causes for NCDs. Data obtained from low- and middle-income countries for this research was sparse, therefore a quality index was utilised to exclude estimates that were considered of less reliability. Doing so lowered the global burden of NCDs caused by infectious factors by approximately 1 percentage point, to 7.4% (Coates et al., 2020). It is therefore vital to consider how these estimates are likely to be representative of a minimum to which additional burden may be added to as more studies are conducted in the future. The lack of quantitative data available in these countries which are most disproportionately impacted by infectious causes of NCDs, further highlights the importance of more comprehensive data collection. Datasets of this nature need to both be more diverse, as well as more specific to avoid biases in analysis and improve estimates.
In conclusion, findings from the present study emphasises the need to address the burden of NCDs that arise from infectious diseases, especially as its impact is greatest in low- and middle-income countries. Strategies for targeting this issue in these regions must consider the disparity in risk factors of NCDs compared to high-income countries, as their populations may be at greater risk of NCDs caused by infectious conditions. Global action has been initiated by the World Health Organisation (WHO) to address the prominent infectious risk factors of NCDs, such as the push for HPV vaccines to eliminate cervical cancer (WHO, 2020). Even so, NCD prevention efforts would still stand to benefit from further expanding its inclusion of infectious causes, as will the ultimate goal of global healthcare equity for all.
References:
Coates, M. M., Kintu, A., Gupta, N., Wroe, E. B., Adler, A. J., Kwan G. F., Park, P. H., Rajbhandari, R., Byrne, A. L., Casey, D. C. & Bukhman, G. (2020) Burden of non-communicable diseases from infectious causes in 2017: a modelling study. The Lancet. 8(12), 1489-1498. Available from: doi: 10.1016/S2214-109X(20)30358-2.
NCDAlliance. (2020) NCDs. Available from: https://ncdalliance.org/why-ncds/NCDs#:~:text=Historically%20considered%20to%20be%20diseases,%2Dincome%20countries%20(LMICs).&text=Many%20NCDs%20are%20preventable%20and,increase%20by%2017%25%20by%202025. [Accessed 29th November 2020]
World Health Organisation. (2020) Human Papillomavirus (HPV) and cervical cancer. Available from: https://www.who.int/news-room/fact-sheets/detail/human-papillomavirus-(hpv)-and-cervical-cancer [Accessed 28th November 2020]
World Health Organisation. (2020) Non-communicable diseases. Available from: https://www.who.int/news-room/fact-sheets/detail/noncommunicable-diseases [Accessed 28th November 2020]Wroblewski, L. E., Peek Jr., R. M. & Wilson, K. T. (2010) Helicobacter pylori and Gastric Cancer: Factors that Modulate Disease Risk. American Society for Microbiology. 23(4), 713-739. Available from: doi: 10.1128/CMR.00011-10.
Imperial Bioscience Review 