Thursday, July 24, 2008

BMJ Articles on Tackling Aging (Update #2)

Following on from my previous entry, how does the aspiration to retard human aging figure in the "big picture" of the challenges facing humanity this century? Yes the diseases of aging ravage (and will continue to ravage) those living in the most affluent countries of the world, but what about the rest of the world? Is aging a problem for middle-income and low-income countries? Here I gather a few stats to help us get a handle on this issue.

Let's start by considering how many humans die each year in the world. How many people do you think die in any given year? 20 million? 30 million? Higher? And what do you think kills most people? Is it war? Climate change? Starvation?

The first question is easier to answer than the second. It is not always easy to determine the "cause of death" because it is often the case that many different things lead to a person's death.

But if we venture over to this site at the World Health Organization, we see that in the year 2002 approximately 57 million people died. Furthermore, "cardiovascular diseases kill more people each year--in high, middle- and low-income countries alike--than any others. In 2002, 7.2 million people died of coronary heart disease, 5.5 million from stroke or another form of cerebrovascular disease".

The WHO designation between "rich", "middle" and "low-income" countries helps provide us with a useful overview of the role of aging in disease and disadvantage world-wide. Unfortunately I am having difficulty finding out which countries the WHO includes in each category so that we can get a sense of the numbers of people we are talking about...

Ah, after digging around for a while I found something which indicated that WHO follows the categories used by the World, heading over there, we see that middle-income countries account for almost half of the world's population. And you can see a map of these 86 countries here.

Let's stop here for a moment and consider the case of the world's largest country- China. What are the 3 leading causes of death in a middle-income country like China, and how do they compare to a rich country like the U.S.? I suspect many people will think the 3 leading of causes of death are very different, but they are in fact *identical*. This study on deaths in China puts the 3 top causes of death as cancer, heart disease and cerebrovascular disease. And if you head over to this CDC site for the US you see the same top 3 causes of death. This is very telling. And it helps us see the role age-related diseases play in most of the world (rich and middle-income countries).

So if we go back to this WHO site we see them explain the different patterns of death that occur in rich, middle and low-income countries. They summarise it as follows:

In high-income countries more than two-thirds of all people live beyond the age of 70 and die of chronic diseases: cardiovascular disease, chronic obstructive lung disease, cancers, diabetes or dementia. Lung infection remains the only leading infectious cause of death.

In middle-income countries, nearly half of all people live to the age of 70 and chronic diseases are the major killers, just as they are in high-income countries. Unlike in high-income countries, however, HIV/AIDS, complications of pregnancy and childbirth and road traffic accidents also are leading causes of death.

In low-income countries less than a quarter of all people reach the age of 70, and nearly a third of all deaths are among children under 14. Although cardiovascular diseases together represent the leading cause of death in these countries, infectious diseases (above all HIV/AIDS, lung infections, tuberculosis, diarrhoeal diseases and malaria) together claim more lives. Complications of pregnancy and childbirth together continue to be a leading cause of death, claiming the lives of both infants and mothers.

Even in low-income countries age-related disadvantage causes suffering and death. Of course it is dwarfed by the human and economic cost of early death and disease. But it is false to describe the afflictions of aging (like cancer, heart disease, diabetes, etc.) as just problems for the richest countries of the world. They afflict all countries, though in varying degrees. But the variation is not that great once a country has made serious headway on deaths among the young, even if the countries are very unequal with respect to wealth and income. Furthermore, aging also impacts the gender balance, as this site notes:

Women comprise the majority of the older population in virtually all countries, largely because globally women live longer than men. By 2025, both the proportion and number of older women are expected to soar from 107 to 373 million in Asia, and from 13 to 46 million in Africa.

And so when tackling aging we need to think about the life prospects of the hundreds of millions of aged women that will be living in Asian and Africa this century. Retarding aging would help them enjoy greater health and vigour in later life. The goal of tackling aging would not simply benefit those in the richest countries. Everyone, rich and poor, would benefit.

To see how countries that are less affluent still suffer from chronic diseases compare, for example, this chart with this one. The first chart examines the state of chronic illness in the rich countries. Death by chronic diseases are set to rise. Why? Because these populations are experiencing the cellular and molecular damage of senescence. Even lower middle-income countries are suffering this same fate, as deaths from diabetes are set to rise by 48%. Now of course aging is not the only factor at play here. So are changes in eating habits and lifestyle. But these drastic expected rises in the chronic diseases would be significantly lower if all the adults living in these countries were 20 years of age.** As noted before, being 20 years of age is often a very effective shield (though not full-proof) against chronic diseases like cancer and heart disease. Aging dramatically increases our risk for these diseases, and all other age-related disadvantage. And so it is imperative not to lose sight of this fact. For if we do, we will take a much more limited view of the potential prescriptions for addressing these pressing problems.

So what have we learned from this brief foray into the world's leading causes of death? The first thing to take away is that there are many, many problems to be addressed. These range from child mortality and HIV, to car accidents and suicide. But there is no denying the fact that aging will be implicated in the vast majority of deaths among the world's current 6.6 billion plus population.

Of course causes of death are not the only thing that matters. And if senescence quietly and peacefully took the lives of still healthy and productive humans while they slept at night things might look different. But that is not how aging works (though it might if we retard aging, as that might also compress morbidity and mortality!). The diseases of aging are *chronic*. Aging makes us extremely vulnerable to many different horrible things, so that we spend many years frail and diseased. It also puts enormous strains on health care resources and age-entitlement programs like state pensions.

Given all this, you would think there is a well-funded, global, rational plan for tackling the challenges of aging. Sadly there is not. And that makes the challenge of tackling aging even more of a challenge!


*the chart above is from this WHO site.

** UPDATE: looking up some further numbers on the age of death for chronic diseases in the world I came across this useful WHO report. In the year 2005, chronic diseases killed 35 million people worldwide. That number is twice the number of deaths due to infectious diseases (including HIV/AIDS, tuberculosis and malaria), maternal and perinatal
conditions, and nutritional deficiencies combined.

And once we consider the age groups that die from chronic conditions, across the global, we see that over 75% (27 of the 35 million) of deaths from chronic disease occur among those aged 60 or over. Death from chronic diseases account for 1.6 million deaths worldwide for people under the age of 30.

And so these numbers help us get a sense of what the future holds for the world's aging population. Unless we tackle preventative measures for these chronic conditions, the world's aging populations will be ravaged by the diseases of aging.