Editor’s note: The 17th IASP World Congress on Pain took place September 12-16, 2018, in Boston, US. At the Congress, 12 early-career pain researchers took part in the PRF Correspondents Program, a science communications training experience that provides participants with knowledge and skills needed to communicate science effectively to a wide range of pain researchers and to patients and the wider public. As part of this program, the participants provided first-hand reporting from plenary sessions. Here, Alisa Johnson, PhD, a postdoctoral research associate at the University of Florida, Gainesville, US, reports on a lecture delivered by plenary speaker Fiona Blyth, University of Sydney, Australia.
Although pain researchers have put tremendous effort into understanding the impact of pain at an individual level, population effects up to now have been largely ignored. At the International Association for the Study of Pain’s 17th World Congress on Pain, Fiona Blyth, University of Sydney, Australia, presented a compelling argument for the need for a global scientific and policy response to the problem of chronic pain, which will be of critical importance to improving health at a population level.
Blyth noted the frustration and difficulties many pain researchers experience when trying to inform governments and funders of the size of the problem and the unmet need of chronic pain. In her talk, she stressed that low back pain is now the leading specific cause of disability and non-fatal disease burden worldwide, yet has received little attention from global policy makers.
Understanding the burden of disease
Historically, burden of disease assessments have focused predominantly on diseases that carry a high fatal burden, while diseases with high non-fatal health burden have been largely ignored. Early attempts to understand causes of mortality at the population level began in the 1600s. At that time, nearly 75 percent of all deaths were due to infectious diseases, malnutrition, and complications of childbirth. Cardiovascular disease and cancer only accounted for 6 percent of deaths, and other chronic conditions were represented in such small numbers, if at all, and were indistinguishable as separate causes of mortality. As life expectancy increased in the mid-20th century, non-fatal health loss became a more relevant issue when assessing disease burden.
Internationally, burden of disease has been assessed since the 1990s through the Global Burden of Disease (GBD) project sponsored by the World Health Organization, the Bill and Melinda Gates Foundation, and other partners. The Institute for Health Metrics and Evaluation (IHME) at the University of Washington, Seattle, serves as the global hub for the GBD project and houses a wealth of global health metrics. The methods used in the GBD project have been highly influential in funding decisions regarding health programs at the national and international levels.
The GBD project utilizes uniform measures across countries and conditions, and assesses mortality and disability factors associated with more than 300 diseases and injuries and 84 common risk factors across 195 countries. The core measure used to determine GBD is the disability-adjusted life years (DALYs) measure. This comprises two other measures―years of life lost (YLLs) and years of life lived with a disability (YLDs)―and it encapsulates how disease can affect us in one of two ways. As Blyth explained, one can conceptualize the ideal condition in which maximum life expectancy is lived out completely in full health. Then, if one dies prematurely in full health, this results in YLLs. Or, one might live the first part of life in full health but spend the second part of life in less than full health. This represents YLDs. These two measures, YLLs and YLDs, are then combined to form the DALYs measure, which is simply the sum of the two.
“We have this issue of the loudest voice, which is that death dominates the framing of burden of disease measurement, and it’s problematic for pain and other high burden conditions that have a large but non-fatal burden and a relatively low fatal burden,” Blyth told the audience. But diseases and injuries with a low fatal burden still carry substantial risk of disability, health loss, and reduced quality of life, and yet have received little attention from a global health perspective.
Determining the global burden of a pain condition
To reach a burden of disease estimate, Blyth used the example of low back pain (LBP). In this case, one would first need to find high-quality epidemiological studies conducted within a country that accomplished a number of objectives, including identification of common patterns of pain in LBP, such as whether the pain is acute or chronic, or whether the pain is radiating or not; use of agreed-upon and standardized definitions of LBP; measurement of different levels of pain severity; and incorporation of rates of incidence, prevalence, and duration, along with associations with premature mortality within the population.
Once this is achieved, then LBP would be randomly compared to one of the other 300+ conditions that are currently monitored in GBD to establish a disability weight for LBP. Disability weights are established through the administration of thousands of population surveys in many different countries. In these surveys, respondents are given a description of two randomly paired conditions, for example, LBP and impaired vision, and asked to rate which person—one with LBP versus one with impaired vision—is in better health. These ratings are then used to determine the relative burden of each condition.
A 2010 GBD review article (Murray and Lopez, 2013) noted that LBP had the highest disability burden and the sixth highest disease burden overall (fatal and non-fatal disease burden). Additionally, musculoskeletal disorders, including LBP, accounted for roughly 21 percent of the total global disability burden, with only mental disorders accounting for a larger percentage (approximately 23 percent). Blyth pointed out that, as noted in the article, the burden of LBP has increased from the years 1990 to 2010. According to 2016 estimates, LBP remains the leading cause of non-fatal health burden globally in both developed and developing countries, and this is expected to remain the case as the global population ages.
A critical tipping point
In the last five years, Blyth said a critical “tipping point” has been reached where non-fatal burden has become the biggest contributor to GBD. To date, GBD has focused primarily on the “Big Four” non-communicable diseases (cardiovascular disease, chronic respiratory disease, diabetes, and cancer). While it is tremendously important to reduce mortality associated with these diseases, it is also equally important that as people live longer, they are able to maintain health-related quality of life. Blyth pointed out that even though pain is the leading contributor to the global burden of disability and non-fatal burden of disease, there is still a large unmeasured pain burden in the worldwide population. For example, the pain and treatment burden of migraine and other headache types, diabetic neuropathy, HIV and other infection-related neuropathies, trauma pain, cancer pain, and persistent postsurgical pain have not been well characterized.
In addition, common risk factors associated with a range of diseases have been assessed in GBD studies. These are grouped into three categories: behavioral risk factors, such as smoking and physical activity; environmental/occupational risk factors, such as unsafe water and air pollution; and metabolic risk factors, such as body mass index and high plasma glucose. Together these risk factors account for nearly 60 percent of overall GBD fatal burden. But in the case of LBP and neck pain, these same risk factors account for only about 23 percent of disability burden. As Blyth noted, since these are the risk factors monitored in GBD and are the targets of interventions to reduce GBD, focusing on these risk factors limits the ability to determine the actual global impact of pain on populations and effectually reduce pain burden.
An aging population
Chronic pain is age related, and as population aging continues to increase, the prevalence of chronic pain is expected to rise. In developed countries, two themes have emerged. First, people are living longer, but for the majority of us the extra years of life are not years of full health because of comorbidities. Therefore, pain must be considered in the context of multiple chronic health conditions that aging individuals have. Second, subgroups of people living beyond 100 years of age are amongst the most rapidly growing in the population. Among these subgroups are “super-agers” who have a delayed onset of chronic disease morbidity, yet very little is known about their pain experience.
However, Blyth pointed out, the story in developing countries is very different. Among those countries, population aging is occurring at a much quicker rate. For example, the rate of population increase among adults aged 60 and over in Sub-Saharan Africa is progressing much faster than rates of increase in developed countries, with a projection of 155 million people aged 60 and over by the year 2050. This is more than double the rate of increase in the same age group in Western Europe, which is projected to have 64 million people aged 60 and over by 2050.
Overall, estimates predict that by 2050 there will be 1.25 billion people aged 60 and over in the world, and that approximately two-thirds of those aged 65 years and over will reside in Asia (WHO World Report on Ageing and Health, 2015). With these projections come serious concerns regarding the impact chronic pain will have on health loss and disease burden globally, particularly in those countries with the fewest resources.
A global response to pain
Global scientific and policy responses to the problem of pain are needed to “connect evidence with its implementation in policy,” Blyth said. As a starting point, she outlined a scientific agenda that includes seven key features to improve estimates of global pain burden, and calling for an expanded set of pain conditions; pain-specific coding; agreed-upon definitions of major pain conditions at the population level; more consistent and comprehensive descriptions of relevant characteristics of common pain conditions at the population level, including duration, severity, and demographic trends; more comprehensive mapping of pain conditions within the existing GBD framework; high-quality studies to determine potential fatal burden associated with pain; and an increased focus on enabling studies in resource-limited countries, like a recent study conducted for the Solomon Islands (Hoy et al., 2018). Additionally, these responses need to be tailored to address issues relevant to high- and low-resource settings, including data gaps and delivery of interventions.
Blyth also described what a comprehensive policy response to pain would look like. In particular, she pointed to three evidence translation steps. The first step is to establish the size of the burden of pain, which would raise awareness of pain in the global health policy agenda, highlight the relative importance of the global pain burden, and could be used to develop messages about the societal and economic burden of pain. The second step is to take the lessons learned from integrated, system-level approaches used to address other non-communicable diseases, especially in low-resource settings, and apply them to pain. This would include developing positive messages about the individual and societal benefits of maintaining and maximizing function, and highlighting the importance of reducing non-fatal disease burden. Finally, in order to prevent new cases, the third step is to address the underlying causes of pain, thereby reducing overall global disease burden.
It’s time for change
Blyth concluded her talk by reminding the audience of three essential points. First, the global burden of pain is not yet fully measured, but existing evidence shows that it is a leading contributor to global disability. Second, the aging of the population, particularly in developing countries, is and will remain a powerful force in driving the global pain burden. Third, collectively, pain researchers now have enough evidence to make the case for a global policy response to the problem of chronic pain and the tools to bring about change.
Alisa Johnson, PhD, is a postdoctoral research associate at the University of Florida, Gainesville, US.
Image credit: Thomas Price/123RF Stock Photo.