Gina Kolata of the New York Times has written a great article surveying the building body of evidence which shows earlier generations got classic diseases of old age sooner and did so due to infections while very young and poorer nutrition. (and I strongly urge you to read the full article)
New research from around the world has begun to reveal a picture of humans today that is so different from what it was in the past that scientists say they are startled. Over the past 100 years, says one researcher, Robert W. Fogel of the University of Chicago, humans in the industrialized world have undergone “a form of evolution that is unique not only to humankind, but unique among the 7,000 or so generations of humans who have ever inhabited the earth.”
We humans alive today are physically way different on average as compared to previous generations.
In previous centuries heart disease, lung disease, and other ailments showed up decades earlier in human lives.
The biggest surprise emerging from the new studies is that many chronic ailments like heart disease, lung disease and arthritis are occurring an average of 10 to 25 years later than they used to. There is also less disability among older people today, according to a federal study that directly measures it. And that is not just because medical treatments like cataract surgery keep people functioning. Human bodies are simply not breaking down the way they did before.
What is most interesting about these results are the suspected causes: events in the womb and while still quite young can set people up for chronic diseases decades later.
The proposed reasons are as unexpected as the changes themselves. Improved medical care is only part of the explanation; studies suggest that the effects seem to have been set in motion by events early in life, even in the womb, that show up in middle and old age.
“What happens before the age of 2 has a permanent, lasting effect on your health, and that includes aging,” said Dr. David J. P. Barker, a professor of medicine at Oregon Health and Science University in Portland and a professor of epidemiology at the University of Southampton in England.
But it is too late for us to go back in time and tell our mothers to avoid people with colds and flus and other infectious diseases. Our bodies are damaged even from before birth. To fix that damage we need gene therapy, stem cells, and the rest of the panoply of coming rejuvenation therapies.
We are taller, heavier, live longer, get sick later. Almost half of 65 year olds can expect to reach 85. I want that percentage to rise much higher.
In 1900, 13 percent of people who were 65 could expect to see 85. Now, nearly half of 65-year-olds can expect to live that long.
People even look different today. American men, for example, are nearly 3 inches taller than they were 100 years ago and about 50 pounds heavier.
One factor that is different today is that we get infected less and suffer from infections for shorter periods of time. Improved hygiene (e.g. refrigerators and a variety of methods of killing and avoiding food borne pathogens), vaccines, antibiotics, better nutrition, and less exposure to extremes of weather all reduce our rates of infectious disease.
Even if one does not die while infected the infectious diseases take their toll and accelerate aging in a number of ways. First off, the pathogens directly do damage to the body. Second, the immune system's response does damage. In the process of attacking pathogens the immune response causes collateral damage to human tissue. Chemical compounds released by immune cells do damage to our own cells. Third, infection reduces our ability to stay nourished due to decreased appetite, diarrhea, decreased ability to do activities that bring in food, and other mechanisms. Therefore a reduction in infectious disease exposure has reduced the rate at which our bodies accumulate damage.
Conventional wisdom has it that people live longer today because when they do get sick medical treatments can keep them alive. But Dr. Fogel's study of US Civil War veteran medical records shows that back then people got serious illnesses at much younger ages, decades sooner. They lived with these illnesses for much of their lives.
Instead of inferring health from causes of death on death certificates, Dr. Fogel and his colleagues looked at health throughout life. They used the daily military history of each regiment in which each veteran served, which showed who was sick and for how long; census manuscripts; public health records; pension records; doctors’ certificates showing the results of periodic examinations of the pensioners; and death certificates.
They discovered that almost everyone of the Civil War generation was plagued by life-sapping illnesses, suffering for decades. And these were not some unusual subset of American men — 65 percent of the male population ages 18 to 25 signed up to serve in the Union Army. “They presumably thought they were fit enough to serve,” Dr. Fogel said.
Suddenly travel to the past in a time machine has gotten a lot less attractive. Even if one could go back with even more vaccines than we have today the environment back then would take a heavy toll. Though if you could go back and get rich and choose a less severe environment you could buffer yourself from some of the ravages of previous eras.
Note that people living back in the 1800s ate what today would be considered a much more natural diet. No pesticides. No trans fatty acids on french fries. But they had a much higher incidence of heart disease.
Eighty percent had heart disease by the time they were 60, compared with less than 50 percent today. By ages 65 to 74, 55 percent of the Union Army veterans had back problems. The comparable figure today is 35 percent.
That higher rate of heart disease could at least in part be due to chronic infections.
Economist Douglas V. Almond at Columbia University examined health records of children born around the time of the great killer 1918 influenza pandemic and found that women were pregnant during the pandemic gave birth to children who fared much worse by several measures as compared to children born right before or after the pandemic.
To his astonishment, Dr. Almond found that the children of women who were pregnant during the influenza epidemic had more illness, especially diabetes, for which the incidence was 20 percent higher by age 61. They also got less education — they were 15 percent less likely to graduate from high school. The men’s incomes were 5 percent to 7 percent lower, and the families were more likely to receive public assistance.
The effects, Dr. Almond said, occurred in whites and nonwhites, in rich and poor, in men and women. He convinced himself, he said, that there was something to the Barker hypothesis.
Pet peeve: I think employers should organize workplaces to reduce the incidence of diseases transmission at work. Discourage sick people from working. I hate hearing people coughing over the cubicle walls and then seeing other people getting sick. Not only does this cost economically but it is probably also shortening our lifespans. Workplace doors, bathrooms, kitchens, and other locations could be reworked to reduce touching of common surfaces.
You wash your hands in the lavatory sink but have to turn the turn the faucet handle to turn off the water (how about foot pedals?) and then turn a door handle to get out of the room. Low cubicle walls also allow cough droplets to travel across a room. In workplaces where employers push wellness programs on employees shouldn't the employers put more effort into reducing our odds of getting sick while at work?
These results go a long way toward confirming the arguments of evolutionary theorists Gregory Cochran and Paul Ewald that the role of infections in causing chronic illnesses has been much underestimated.
|Share |||Randall Parker, 2006 July 30 02:23 PM Aging Studies|