Global Rise in Total AD Cases Dwarfs Falling Age-Standardized Rate

As populations age around the world, the number of deaths due to Alzheimer’s and other dementias is up almost 40 percent since 2005, according to the latest figures in the Global Burden of Disease (GBD) Study 2015. At the same time, a small dip in the age-standardized rate of death could mean that improved vascular and overall health, as well as education, may be tempering that ever so slightly. The report was a collaboration between the Institute for Health Metrics and Evaluation (IHME) and The Lancet, and appears in the October 8 issue of the journal. In a series of seven papers, the report outlines the causes of death and disability in regions and countries around the world. “This study gives a sense of the burden of dementia, and how it scales compared to different diseases in the population,” said Eric Larson of the Group Health Research Institute in Seattle. “It’s a global perspective on disease and how it’s changing.”

An Interactive Tool: The GBD Compare tool allows users to query global causes of mortality and morbidity by age, sex, and region. Here, more deaths from dementias (red areas) occur in North America and Europe, while fewer people die with the disease in Africa and Eastern Europe (blue). IHME, University of Washington, 2016. (Accessed Oct. 14, 2016.)

This is the third report since GBD 2010 and GBD 2013 were published (Dec 2012 news). By detailing the major diseases, injuries, and other health risks that challenge health systems worldwide, GBD authors aim to provide policymakers with up-to-date information. Trends in AD and dementia have remained largely steady over that time, but the data come into sharper focus as new information flows in and researchers find new ways to analyze the data.

In one GBD 2015 paper, first author Haidong Wang at IHME and colleagues reported trends for 249 causes of death in 195 countries between 1980 and 2015. The number of people dying from Alzheimer’s disease and related dementias has risen 38 percent in the last 10 years. “Globally a lot of [other] causes of death are declining,” said Theo Vos, University of Washington, Seattle, a joint senior author on the paper. He cited deaths due to childhood and infectious diseases as examples. "But since we have no effective treatments or preventative measures for dementia, and we have an aging global population, Alzheimer’s is becoming much more important in terms of rank order.”

The rising death toll from AD is slightly offset by a 2.7 percent drop in the age-standardized death rate. That method of looking at the data removes the effects of population growth and aging, said Vos. “This leaves a more level field comparison for the true epidemiological change [in AD].” A small decrease could reflect improved cardiovascular health, better education, or higher overall health. It fits with declines in prevalence and incidence reported in studies from the United Kingdom, Germany, and United States respectively (July 2013 news; Satizabal et al., 2016). However, some data suggest the incidence of dementia is rising in the developing world (May 2012 news). “These data are useful at the ‘global burden’ level; however, it is probably impossible to reconcile the empirical number with epidemiologic data on incidence, survival, and prevalence,” wrote Walter Rocca, Mayo Clinic, Rochester, Minnesota, to Alzforum. “The trends may be very different by region, and the global numbers are weighted averages of possibly opposing trends.”

In the grand scheme of things, the 2.7 percent reduction suggests that the death rate among prevalent cases of dementia has not changed much, said Vos. Any dip will be far outstripped by increases due to population aging, he said, causing significant strain on health systems worldwide.

A companion paper on which Vos is the first author extends these findings by reporting that AD and other dementias are also becoming a leading cause of disability during life (GBD 2015 Disease and Injury Incidence and Prevalence Collaborators, 2016). Among people 75 and older, AD has now made its first appearance among the top 10 causes of disability around the globe. According to another companion paper, dementias are a growing reason for rising disability-adjusted life-years (DALYs), which reflect the years of healthy life lost due to premature mortality and years lived with disability (GBD 2015 DALYs and HALE Collaborators, 2016). Alzheimer’s and related diseases have caused a 30 percent rise and have become the 29th leading cause of DALYs around the world since 2005, the authors report.  

“The paradox of our era is that as health indicators have improved globally, more people are spending more time with functional health loss, and morbidity is increasing in absolute terms,” wrote Kevin Watkins of Save the Children U.K. in London in an accompanying commentary. “This has far-reaching implications not just for health-system financing and service delivery, but also for economic growth and well-being.”

To allow researchers to explore these data in greater detail, GBD collaborators have created the GBD Compare tool. Users can enter factors they’d like to compare—such as causes of death or disability by age and sex—to explore global trends in disease and disability.—Gwyneth Dickey Zakaib

Comments

    • User Profile Image Marcia Ratner
      Boston University Chobanian & Avedisian School of Medicine
    • Posted:

    Ironically, as industrialization expands across the globe so does the lifetime risk for developing AD. But the occupational and environmental risk factors that have been implicated in contributing to lifetime risk of neurodegenerative disease, as well as to subclinical disease progression and thus to a younger age at disease onset, have not been entirely eliminated from the equation, even though these factors have been substantially reduced in more advanced countries of the world. Occupational exposures to elevated levels of neurotoxic chemicals tend to occur in the immediate work space of at-risk employees. Thus, from a global public health perspective, the rapid implementation of improved industrial hygiene practices and enforcement of workplace exposure limits aimed at curtailing neurotoxic chemical exposures in developing nations is extremely prudent.

    View all comments by Marcia Ratner

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References

News Citations

  1. Research Brief: Around the Globe, More People Die of Dementia
  2. Dementia Prevalence Falls in England
  3. Dementia Numbers in Developing World Point to Global Epidemic

Paper Citations

  1. Satizabal C, Beiser AS, Seshadri S. Incidence of Dementia over Three Decades in the Framingham Heart Study. N Engl J Med. 2016 Jul 7;375(1):93-4. PubMed.
  2. GBD 2015 Disease and Injury Incidence and Prevalence Collaborators. Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016 Oct 8;388(10053):1545-1602. PubMed.
  3. GBD 2015 DALYs and HALE Collaborators. Global, regional, and national disability-adjusted life-years (DALYs) for 315 diseases and injuries and healthy life expectancy (HALE), 1990-2015: a systematic analysis for the Global Burden of Disease Study 2015. Lancet. 2016 Oct 8;388(10053):1603-1658. PubMed.

External Citations

  1. GBD 2010
  2. GBD 2013
  3. GBD Compare tool

Further Reading

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