Impact of Age-Related Disease (Why Solve Aging: Part 2)

The top ten causes of death worldwide are:

  1. Ischemic heart disease (17.33% of deaths)

  2. Stroke (10.11% of deaths)

  3. Chronic obstructive pulmonary disease (5.36% of deaths)

  4. Alzheimer’s disease (4.36% of deaths)

  5. Lower respiratory infections such as pneumonia (4.35% of deaths)

  6. Lung cancer (3.12% of deaths)

  7. Diarrheal diseases (3.03% of deaths)

  8. Diabetes (2.63% of deaths)

  9. Road injuries (2.45% of deaths)

  10. Tuberculosis (2.22% of deaths)

Note that seven of these are diseases of aging.  

The risk of cancer and heart disease increase with age[1]


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As does the risk of stroke[2]:

stroke.png

COPD (Chronic Obstructive Pulmonary Disease):

COPD.png

Alzheimer’s disease and dementia[4]:

alzheimer's.png

Severe pneumonia[5]:

pneumonia.png

and diabetes[6]

diabetes.png

These are all diseases of aging; the primary risk factor is age.

Now let’s look at DALY burden:


DALY.png

The biggest causes of disability worldwide are

  1. Ischemic heart disease (7.32% of DALYs)

  2. Stroke (4.88% of DALYs)

  3. Lower respiratory infections (3.85% of DALYs)

  4. Low back and neck pain (3.6% of DALYs)

  5. Diarrheal diseases (3.12% of DALYs)

  6. Road injuries (2.99% of DALYs)

  7. Sense organ diseases (2.7% of DALYs)

  8. COPD (2.66% of DALYs)

  9. Preterm birth (2.6% of DALYs)

  10. HIV/AIDS (2.41% of DALYs)

(and if cancers were considered as a single disease, cancer would be the top cause of disability, at 8.5% of DALYs.)

Diseases of aging still constitute a substantial portion of the top causes of disability.

Note that low back pain is also an age-associated condition.



backpain.png

Sense organ disabilities are also age-related. 81% of blind or vision-impaired people are over 50[7] since the most common causes of blindness are the age-related diseases of cataracts, age-related macular degeneration, glaucoma, and diabetic retinopathy. The global prevalence of deafness also increases with age[8]:

deafness.png

So six or seven out of the top ten causes of disability worldwide, depending on how you count cancers, are age-related diseases.

Age-related diseases, in total, cause about a third of all disability and the majority of all deaths worldwide.

Self-Reported Happiness and Values

Ok, so diseases of aging cause a lot of death and disability. But do they cause a lot of suffering?  Do they matter to people?  After all, the news doesn’t report on chronic disease as much as violence or politics.  It might be that people are relatively content to have their health decline with age.

However, it looks like the worldwide self-report data shows that health ranks at or near the top of people’s priorities and the correlates of happiness.

DALYs are calculated based on how non-disabled people would rate the severity of a disability or illness[9], and it’s possible that these people would make systematic errors in imagining what it would be like to have that disability or illness.  In fact, this turns out to be the case. When people self-assess their actual life satisfaction and happiness, they give more weight to mental health than they do when they’re considering hypothetical situations, while people care less about physical pain and loss of mobility in real life than they imagine they would in hypothetical situations.[10]  In other words, mental illness is subjectively worse to live through than nondisabled people imagine, and physical disability is subjectively less bad than nondisabled people imagine.


On the other hand, the happiness data does seem to roughly suggest that more severe DALY burden and mortality goes along with less happiness.

Globally, life satisfaction and life expectancy correlate:



And people entering severe disability suffer a sustained loss in life satisfaction[11]:

In the Gallup World Poll, health is positively correlated (r=0.25, p<0.01) with life satisfaction across countries, but it’s not the largest effect; social support and GDP have larger correlations.[12]

In the World Values Survey, the largest effect size on life satisfaction (correlation coefficient/standard deviation) was from log of income, at 65, followed by self-reported “excellent health”, at 33.6.  Other factors measured were age, sex, marital status, employment status, education level, and number of children.[12]

According to a 43-country Pew Research poll[13], people were most likely to rate as “very important” good health (68%), good education for children (65%), safety from crime (64%), and owning a home (62%). According to a Gallup poll, Americans rate family and health as the most important aspects in life, more than work, friends, money, religion, leisure, hobbies, and communities.[14]


If you’re prioritizing by people’s own assessments of their lives, health still appears to be people’s top priority and one of the top drivers of happiness around the world. But there are some factors that make this picture more equivocal. Old people, relative to young people, are the sickest but also the happiest. Income, fairly consistently across studies, matters to happiness more than health.  And DALY ratings will tend to over-weight the severity of physical pain and impairment and under-weight the severity of mental illness, compared to the self-reports of people who actually experience those conditions. But, on the whole, the self-report data doesn’t give us much reason to doubt the common-sense view that age-related diseases cause a lot of human suffering and most people would prioritize avoiding them.

Near-Future Trends

If we take into account near-term trends, age-related disease looks like an even higher priority.  

The world population is aging, as developed and developing nations go through a demographic transition:



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Meanwhile, extreme poverty worldwide is dropping:

poverty.png

Given these trends, we’d expect death and disability due to age-related disease to be rising, since these diseases are more common in the elderly and many of them (like cancer and Alzheimer’s) are not very treatable.  Meanwhile, we’d expect death and disability due to non-age-related infectious disease to be dropping, since many of these diseases are easily preventable or treatable with modern medicine, and access to the relevant health care is limited only by extreme poverty, which is declining worldwide.

Indeed, we do see this pattern in the global DALY rankings from 1990 to 2016.


dalyranking.png

The health problems whose ranking increased in the past 20 years are cardiovascular diseases, cancer, mental illness, musculoskeletal disorders, diabetes and endocrine disorders, diabetes and endocrine disorders, neurological disorders, and cirrhosis.  All of these but mental illness are diseases of aging; note that neurological disorders include Alzheimer’s and dementia, and musculoskeletal disorders include arthritis. By contrast, the health problems whose ranking decreased are diarrhea and lower respiratory illnesses, neonatal disorders, unintentional injuries, neglected tropical diseases and malaria, chronic respiratory disorders, nutritional diseases, and other infectious diseases.  Mostly infectious diseases and diseases of severe poverty, and not (with the exception of chronic respiratory disease) diseases of aging.

As the world ages and gets richer, the problems of the future are going to be shifted towards age-related disease (and towards mental illness, which may be a disease of urbanization.[15])  

Conclusion

If you care about preventing death and suffering worldwide, the diseases of aging loom large. They’re not just problems for rich countries. The whole world is aging, and increasingly dying from chronic diseases of aging.  Health is consistently near the top of what people worldwide value most and what makes them happy with their lives; a big chunk of human wellbeing, in the present and near future, depends on whether we can do something about the diseases of aging.



References

[1]Driver, Jane A., et al. "Incidence of cardiovascular disease and cancer in advanced age: prospective cohort study." Bmj337 (2008): a2467.

[2]Seshadri, Sudha, and Philip A. Wolf. "Lifetime risk of stroke and dementia: current concepts, and estimates from the Framingham Study." The Lancet Neurology 6.12 (2007): 1106-1114.

[3]https://www.cdc.gov/nchs/products/databriefs/db63.htm

[4]Rocca WA, Petersen RC, et al.: Trends in the incidence and prevalence of Alzheimer's disease, dementia, and cognitive impairment in the United States. Alzheimer Dement. 2011;7(1):80-93.

[5]Griffin, Marie R., et al. "US hospitalizations for pneumonia after a decade of pneumococcal vaccination." New England Journal of Medicine 369.2 (2013): 155-163.

[6]Whiting David R.. IDF Diabetes Atlas: Global estimates of the prevalence of diabetes for 2011 and 2030. Diabetes Research and Clinical Practice. Elsevier BV; 94(3):311-321.

[7]http://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment

[8]Stevens, Gretchen, et al. "Global and regional hearing impairment prevalence: an analysis of 42 studies in 29 countries." The European Journal of Public Health 23.1 (2011): 146-152.

[9]Salomon, Joshua A., et al. "Disability weights for the Global Burden of Disease 2013 study." The Lancet Global Health3.11 (2015): e712-e723.

[10]https://www.ohe.org/publications/using-happiness-value-health#

[11]https://ourworldindata.org/happiness-and-life-satisfaction#correlates-determinants-and-consequences

[12]Helliwell, John, Richard Layard, and Jeffrey Sachs. "World happiness report." (2012).

[13]http://www.pewglobal.org/2014/10/30/people-in-emerging-markets-catch-up-to-advanced-economies-in-life-satisfaction/

[14]https://news.gallup.com/poll/7504/family-health-most-important-aspects-life.aspx

[15]Gruebner, Oliver, et al. "Cities and mental health." Deutsches Ärzteblatt International 114.8 (2017): 121.