When public-health researcher Tolullah Oni travelled from London to South Africa to study HIV, she soon realized she would have to broaden her focus. Physicians there were grappling with twin epidemics — HIV and tuberculosis. The infections often coincide, and so clinicians were working to integrate their treatment of the two diseases.
But Oni found that many of her patients were dealing with a third problem. “We started seeing people who came in with good adherence to their medicines, but somehow someone had missed the fact that their blood pressure was through the roof,” she says. To bring them back to health, she would need to treat non-communicable diseases such as high blood pressure and diabetes as well. “We were treating conditions and not people.” Oni went on to study the phenomenon in her patient community (T. Oni et al. BMC Infect. Dis. 15, 20; 2015) and is hoping to take the lessons learnt from integrating care of HIV and tuberculosis and apply them to other combinations of diseases.
People are complicated, and their medical problems rarely come neatly packaged as the single diseases that scientists and doctors study. A report released on 19 April by the UK Academy of Medical Sciences details the challenges of studying and treating individuals who have multiple medical conditions, known as multimorbidity. Variations in the definition and frequency of multimorbidity across populations have led to wide estimates of its prevalence, ranging from 13% to 95% of patients globally. The report offers a list of recommendations on what health-care providers can do to address the problem of multimorbidity, and identifies the knowledge gaps that need to be filled.
Researchers should take heed: if their work is to translate to the real world, more scientists — at the clinic and the bench — should shift their focus to look at interactions between disorders.
Multimorbidity seems to be growing in countries where the population is ageing and thus more people are living with chronic diseases, and in countries grappling with chronic infectious diseases such as HIV. Health-care providers should look again at how doctors tend to specialize in specific disorders, when it might be better to arm them with the ability to recognize and treat a range of conditions.
Clinical trials have historically focused on single diseases. They often exclude participants with other conditions to boost the chance of getting a cleaner data set (and to reduce risks of unintended harm). But this is beginning to change as part of a push to lower eligibility requirements for many clinical trials. Researchers are also increasingly focusing on supplementing data from carefully controlled clinical trials with ‘real-world evidence’ — much messier data collected from people who may be taking multiple medications and dealing with multiple conditions. Such studies are a good way to start understanding the effects of multimorbidity. In this issue, a World View describes how to make sure people with anxiety disorder and other complications are integrated into clinical research of pain treatments.
There is more to be done. As the report highlights, clinical researchers need to characterize multimorbidity around the world, looking at which conditions are most likely to coincide and in which populations. Already, evidence shows that this varies dramatically by location and wealth. More-deprived individuals in wealthy countries, for example, might be more likely to have multiple chronic diseases; whereas in poorer countries, wealthier individuals might be more likely to have multiple conditions.
Such studies could identify the most prevalent and harmful clusters of disease — and so help to focus basic research. Bench scientists also tend to focus on one disease at a time, even if their work sometimes yields insights into a range of conditions. More effort should be put into studying complex combinations of disorders and how they — and their treatments — interact. Studies of ageing, for example, are detailing the causes of inflammation and its impact on multiple organs in the body (M. N. Bouchlaka et al. J. Exp. Med. 210, 2223–2237; 2013).
This requires support from funders, and a wider recognition that the most tractable projects with the cleanest, easiest to interpret results might not be the most worthy of funding. Studying diseases in combination is challenging, but computational and laboratory tools are increasingly available to handle complex data sets and tease out meaning from messy data.
Some funders are already taking steps in this direction: an upcoming workshop held by UK charity the Wellcome Trust, the UK Medical Research Council and other organizations will look at how research can better tackle multimorbidity. This movement needs support in the coming years. Awareness of multimorbidity has been growing steadily: now the question is how best to deal with it.
Nature 557, 5-6 (2018)