The epidemiological transition theory suggests that a shift from communicable to non-communicable diseases (NCDs) will be observed as countries develop economically and “modernise”. NCDs already cause the death of 41 million people each year, or 71% of all deaths globally, and are projected to increase further. However, it would be naive to disregard other health challenges – increasing burden of some diseases is not associated with a decreasing burden of others. Therefore, a shift in ideas has been observed, introducing concepts such as multimorbidity as alternative explanations.
NCDs cause significant mortality in countries of any socioeconomic status. Cardiovascular diseases are in the top 10 causes of death in both low-, middle- and high-income countries. Other significant contributors to the burden of NCDs are diabetes and cancer. The incidence and prevalence of diabetes have been and continue to grow rapidly worldwide.1,2 The growing incidence will be a main contributor as NCDs overtake infectious diseases as the leading cause of death in low and middle income countries with an expected increase of 110% between 2013 and 2035. Cancers are astonishingly variable and death rates are higher in high-income countries, particularly for lung, colorectal and pancreatic cancer, but some cancers (cervical, head and neck, liver, stomach and oesophageal) cause significant burden in less developed countries too.3 The economic and health system fragility of the poorest countries still prevents them from assuring population-wide prevention and treatment with already existing vaccines and medicines for NCDs. Additionally, a growth of NCDs is experienced in all countries, primarily associated with demographic changes and lifestyle factors.
Thus, NCDs are a great health threat in countries of any socioeconomic status. However, communicable diseases are still a major burden, e.g. tuberculosis, HIV and malaria and more recently the COVID-19 pandemic, which affected virtually every country in the world. It is clear that NCDs are not the only health threat present. To make better sense of the bigger picture, the idea of comorbidity and multimorbidity has been put forward – incorporating frameworks acknowledging multiple morbidities and examining the impact beyond biological interactions.4 For example, various NCDs are risk factors for tuberculosis and HIV, diabetes is a risk factor for malaria and malaria and kidney disease affect each other bidirectionally. Combatting the communicable/NCDdichotomywill benefit disease prevention, promotion, treatment and care.
The current global health situation seems to follow more complex shifts of threats than what the epidemiological transition model suggests. Thus experts have put forward concepts like comorbidity and multimorbidity in order to explain a deeply-rooted interaction of communicable and NCDs, while also considering biological, socioeconomic and environmental factors. In short, NCDs can potentially be the greatest global health threat in the future, but only if we were to drastically counteract a number of other challenges – which is virtually impossible. Therefore, NCDs are not and will not be the biggest health threat, but will coexist and contribute to the burden of other health risks. When it comes to addressing the burden appropriately, in primary research data such as that on treatment effect heterogeneity should be routinely collected in order to account for multimorbidity among patients. This should also be taken into account when designing systematic reviews and meta-analyses, which can inherit all the limitations of an original report. The use of good practice guidelines, such as the ones by Trikalinos et al5 is an appropriate tool in achieving consistency in scientific research. Beyond research, recommendations are necessary for health policy makers as well. The World Health Organisation recommends the following 4 potential solutions in addressing multimorbidity at policy level:6 a systems-based approach to policy making, increasing and strengthening primary care coverage, promoting generalism, and producing guidelines for multimorbidity. Taken together, they would aid much more patient-oriented and effective health policies.