An international projection of life expectancy and major mortality risk paints two scenarios for South Africa by the year 2040: An increase in life expectancy by as much as 12.9 years in the better scenario or decrease by as much as 8.1 years in the worst one.
The study, led by the Institute for Health Metrics and Evaluation at the University of Washington, shows all countries are likely to experience at least a slight increase in lifespans. In contrast, one scenario finds nearly half of all nations could face lower life expectancies.
The rankings of nations’ life expectancies offer new insights into their health status.
South Africa, with an average life expectancy of 62.4 years in 2016, is at present ranked 171st among 195 nations. However, if recent health trends continue it could rise to a rank of 169th in 2040 with an average life expectancy of 69.3 years, an increase of 6.9 years. South Africa’s life expectancy could increase by as much as 12.9 years in a better health scenario or decrease by as much as 8.1 years in a worse health scenario.
In contrast, the US in 2016 ranked 43rd with an average lifespan of 78.7 years. In 2040, life expectancy is forecast to increase only 1.1 years to 79.8, but dropping in rank to 64th. China, on the other hand, had a lifespan of 76.3 years in 2016 and is expected to increase to 81.9, raising its rank from 68th to 39th in 2040.
In addition, the study projects a significant increase in deaths from non-communicable diseases (NCDs), including diabetes, chronic obstructive pulmonary disease (COPD), chronic kidney disease, and lung cancer, as well as worsening health outcomes linked to obesity.
In 2016, the top 10 causes of premature death in South Africa were HIV/Aids, lower respiratory infections, road injuries, interpersonal violence, tuberculosis, diabetes, ischemic heart disease, diarrheal diseases, stroke, and neonatal preterm birth complications. In 2040, however, the leading causes are expected to be diabetes, road injuries, lower respiratory infections, HIV/Aids, interpersonal violence, ischaemic heart disease, tuberculosis, chronic kidney disease, stroke, and diarrhoeal diseases.
However, there is “great potential to alter the downward trajectory of health” by addressing key risk factors, levels of education, and per capita income, authors say.
“The future of the world’s health is not pre-ordained, and there is a wide range of plausible trajectories,” said Dr Kyle Foreman, director of data science at the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, and lead author on the study. “But whether we see significant progress or stagnation depends on how well or poorly health systems address key health drivers.”
The top five health drivers that explain most of the future trajectory for premature mortality are high blood pressure, high body mass index, high blood sugar, tobacco use, and alcohol use, Foreman said. Air pollution ranked sixth.
In addition to China, several other nations are expected in 2040 to increase substantially in their rankings in terms of life expectancy, including: Syria is expected to rise most in rank globally – from 137th in 2016 to 80th in 2040 – likely, according to the authors, due to a conservative model for conflict; Nigeria from 157th to 123rd; and Indonesia from 117th to 100th
In contrast, Palestine is expected to drop the most in its life expectancy ranking – from 114th in 2016 to 152nd in 2040. Moreover, several high-income nations are forecast to drop substantially in their rankings, including: US, dropping the most for high-income countries, from 43rd in 2016 to 64th in 2040; Canada from 17th to 27th; Norway from 12th to 20th; Taiwan (Province of China) from 35th to 42nd; Belgium from 21st to 28th; and the Netherlands from 15th to 21st.
The rankings also find that Spain is expected to place first in the world in 2040 (average lifespan of 85.8 years), a rise from fourth in 2016 (average lifespan of 82.9 years). Japan, ranked first in 2016 (average lifespan 83.7 years), will drop to second place in 2040 (average lifespan 85.7 years).
Rounding out the top 10 for 2040 are: (3) Singapore (average lifespan 85.4 years) ranked third, as compared to 83.3 years in 2016 and ranking also of third; (4) Switzerland (average lifespan 85.2 years), as compared to 83.3 years in 2016 and ranking of second; (5) Portugal (average lifespan 84.5 years), as compared to 81.0 years in 2016 and ranking of 23rd; (6) Italy (average lifespan 84.5 years), as compared to 82.3 years in 2016 and ranking of seventh; (7) Israel (average lifespan 84.4 years), as compared to 82.1 years in 2016 and ranking of 13th; (8) France (average lifespan 84.3 years), as compared to 82.3 years in 2016 and ranking also of eighth; (9) Luxembourg (average lifespan 84.1 years) as compared to 82.2 years in 2016 and ranking of 10th; and (10) Australia (average lifespan 84.1 years), as compared to 82.5 years in 2016 and ranking of fifth.
Among those top 10 nations, even their ‘worse’ scenarios in 2040 remain above 80 years. In stark contrast, the bottom-ranked nations, which include Lesotho, Swaziland, Central African Republic, and South Africa, the “better” and “worse scenarios” in 2040 range from a high of 75.3 years in South Africa (“better” scenario) to a low of 45.3 years in Lesotho (“worse scenario”), a 30-year difference.
“Inequalities will continue to be large,” said IHME director Dr Christopher Murray. “The gap between the ‘better’ and ‘worse’ scenarios will narrow but will still be significant. In a substantial number of countries, too many people will continue earning relatively low incomes, remain poorly educated, and die prematurely. But nations could make faster progress by helping people tackle the major risks, especially smoking and poor diet.”
In a “worse” scenario, life expectancy decreases in nearly half of all countries over the next generation. Specifically, 87 countries will experience a decline, and 57 will see an increase of one year or more. In contrast, in the “better” scenario, 158 countries will see life expectancy gains of at least five years, while 46 nations may see gains of 10 years or more.
The future shift toward increased premature mortality from NCDs and injuries and away from communicable diseases is apparent by the changing proportions of the top 10 causes of premature death.
In 2016, four of the top 10 causes of premature mortality were NCDs or injuries; in contrast, in 2040, that number increases to eight. The eight NCD or injury causes in the top ten in 2040 are expected to be ischemic heart disease, stroke, COPD, chronic kidney disease, Alzheimer’s disease, diabetes, road injuries, and lung cancer.
The study is unprecedented in scope, Foreman said, and provides more robust statistical modelling and more comprehensive and detailed estimates of risk factors and diseases than previous forecasts from the UN and other population studies institutes.
IHME researchers leveraged data from the Global Burden of Disease (GBD) study to produce forecasts and alternative “better” and “worse” scenarios for life expectancy and mortality due to 250 causes of death for 195 countries and territories.
Researchers produced forecasts of independent drivers of health, including socio-demographic measurements of fertility, per capita income, and years of education, along with 79 independent drivers of health such as smoking, high body mass index, and lack of clean water and sanitation. They then used information on how each of these independent drivers affects specific causes of death to develop forecasts of mortality.
“The range of ‘better’ and ‘worse’ scenarios enables stakeholders to examine potential changes to improve health systems – locally, nationally, and globally,” Murray said. “These scenarios offer new insights and help to frame health planning, especially regarding long lag periods between initial investments and their impacts, such as in the research and development of drugs.”
In addition to calling attention to the growing importance of non-communicable diseases, the analysis exposes a substantial risk of HIV/AIDS mortality rebounding, which could undo recent life expectancy gains in several nations in sub-Saharan Africa.
Furthermore, while NCDs are projected to rise in many low-income countries, communicable, maternal, neonatal, and nutritional diseases are likely to remain among the leading causes of early death, thereby creating a “double burden” of disease.
The study is entitled “Forecasting life expectancy, years of life lost, and all-cause and cause-specific mortality for 250 causes of death: reference and alternative scenarios for 2016–40 for 195 countries and territories using data from the Global Burden of Disease Study 2016.”
Summary
Background: Understanding potential trajectories in health and drivers of health is crucial to guiding long-term investments and policy implementation. Past work on forecasting has provided an incomplete landscape of future health scenarios, highlighting a need for a more robust modelling platform from which policy options and potential health trajectories can be assessed. This study provides a novel approach to modelling life expectancy, all-cause mortality and cause of death forecasts —and alternative future scenarios—for 250 causes of death from 2016 to 2040 in 195 countries and territories.
Methods: We modelled 250 causes and cause groups organised by the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) hierarchical cause structure, using GBD 2016 estimates from 1990–2016, to generate predictions for 2017–40. Our modelling framework used data from the GBD 2016 study to systematically account for the relationships between risk factors and health outcomes for 79 independent drivers of health. We developed a three-component model of cause-specific mortality: a component due to changes in risk factors and select interventions; the underlying mortality rate for each cause that is a function of income per capita, educational attainment, and total fertility rate under 25 years and time; and an autoregressive integrated moving average model for unexplained changes correlated with time. We assessed the performance by fitting models with data from 1990–2006 and using these to forecast for 2007–16. Our final model used for generating forecasts and alternative scenarios was fitted to data from 1990–2016. We used this model for 195 countries and territories to generate a reference scenario or forecast through 2040 for each measure by location. Additionally, we generated better health and worse health scenarios based on the 85th and 15th percentiles, respectively, of annualised rates of change across location-years for all the GBD risk factors, income per person, educational attainment, select intervention coverage, and total fertility rate under 25 years in the past. We used the model to generate all-cause age-sex specific mortality, life expectancy, and years of life lost (YLLs) for 250 causes. Scenarios for fertility were also generated and used in a cohort component model to generate population scenarios. For each reference forecast, better health, and worse health scenarios, we generated estimates of mortality and YLLs attributable to each risk factor in the future.
Findings: Globally, most independent drivers of health were forecast to improve by 2040, but 36 were forecast to worsen. As shown by the better health scenarios, greater progress might be possible, yet for some drivers such as high body-mass index (BMI), their toll will rise in the absence of intervention. We forecasted global life expectancy to increase by 4·4 years (95% UI 2·2 to 6·4) for men and 4·4 years (2·1 to 6·4) for women by 2040, but based on better and worse health scenarios, trajectories could range from a gain of 7·8 years (5·9 to 9·8) to a non-significant loss of 0·4 years (–2·8 to 2·2) for men, and an increase of 7·2 years (5·3 to 9·1) to essentially no change (0·1 years [–2·7 to 2·5]) for women. In 2040, Japan, Singapore, Spain, and Switzerland had a forecasted life expectancy exceeding 85 years for both sexes, and 59 countries including China were projected to surpass a life expectancy of 80 years by 2040. At the same time, Central African Republic, Lesotho, Somalia, and Zimbabwe had projected life expectancies below 65 years in 2040, indicating global disparities in survival are likely to persist if current trends hold. Forecasted YLLs showed a rising toll from several non-communicable diseases (NCDs), partly driven by population growth and ageing. Differences between the reference forecast and alternative scenarios were most striking for HIV/AIDS, for which a potential increase of 120·2% (95% UI 67·2–190·3) in YLLs (nearly 118 million) was projected globally from 2016–40 under the worse health scenario. Compared with 2016, NCDs were forecast to account for a greater proportion of YLLs in all GBD regions by 2040 (67·3% of YLLs [95% UI 61·9–72·3] globally); nonetheless, in many lower-income countries, communicable, maternal, neonatal, and nutritional (CMNN) diseases still accounted for a large share of YLLs in 2040 (eg, 53·5% of YLLs [95% UI 48·3–58·5] in Sub-Saharan Africa). There were large gaps for many health risks between the reference forecast and better health scenario for attributable YLLs. In most countries, metabolic risks amenable to health care (eg, high blood pressure and high plasma fasting glucose) and risks best targeted by population-level or intersectoral interventions (eg, tobacco, high BMI, and ambient particulate matter pollution) had some of the largest differences between reference and better health scenarios. The main exception was sub-Saharan Africa, where many risks associated with poverty and lower levels of development (eg, unsafe water and sanitation, household air pollution, and child malnutrition) were projected to still account for substantive disparities between reference and better health scenarios in 2040.
Interpretation: With the present study, we provide a robust, flexible forecasting platform from which reference forecasts and alternative health scenarios can be explored in relation to a wide range of independent drivers of health. Our reference forecast points to overall improvements through 2040 in most countries, yet the range found across better and worse health scenarios renders a precarious vision of the future—a world with accelerating progress from technical innovation but with the potential for worsening health outcomes in the absence of deliberate policy action. For some causes of YLLs, large differences between the reference forecast and alternative scenarios reflect the opportunity to accelerate gains if countries move their trajectories toward better health scenarios—or alarming challenges if countries fall behind their reference forecasts. Generally, decision makers should plan for the likely continued shift toward NCDs and target resources toward the modifiable risks that drive substantial premature mortality. If such modifiable risks are prioritised today, there is opportunity to reduce avoidable mortality in the future. However, CMNN causes and related risks will remain the predominant health priority among lower-income countries. Based on our 2040 worse health scenario, there is a real risk of HIV mortality rebounding if countries lose momentum against the HIV epidemic, jeopardising decades of progress against the disease. Continued technical innovation and increased health spending, including development assistance for health targeted to the world's poorest people, are likely to remain vital components to charting a future where all populations can live full, healthy lives.
Authors
Kyle J Foreman, Neal Marquez, Andrew Dolgert, Kai Fukutaki, Nancy Fullman, Madeline McGaughey, Martin A Pletcher, Amanda E Smith, Kendrick Tang, Chun-Wei Yuan, Jonathan C Brown, Joseph Friedman, Jiawei He, Kyle R Heuton, Mollie Holmberg, Disha J Patel, Patrick Reidy, Austin Carter, Kelly Cercy, Abigail Chapin, Dirk Douwes-Schulz, Tahvi Frank, Falko Goettsch, Patrick Y Liu, Vishnu Nandakumar, Marissa B Reitsma, Vince Reuter, Nafis Sadat, Reed J D Sorensen, Vinay Srinivasan, Rachel L Updike, Hunter York, Alan D Lopez, Rafael Lozano, Stephen S Lim, Ali H Mokdad, Stein Emil Vollset, Christopher J L Murray
[link url="https://cloud.ihme.washington.edu/index.php/s/AkAfRKXFaKwLpFr"]Accompanying collateral materials, including comprehensive listings and supporting data of all nations’ rankings, are available at[/link]
[link url="https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(18)31694-5/fulltext"]The Lancet article summary[/link]