Here's What Will Determine Your Life Expectancy

Looking at 400 million people born between 1800 and 1920, whose information had been collected from public family trees in Ancestry.com, investigator Graham Ruby found that only about 10 percent of human longevity is inherited.

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Here's What Will Determine Your Life Expectancy

Humans inherit money, property and social status, which also influence longevity.


Highlights

  1. Family tree might shed light on health and longevity
  2. Genetics does contribute to life span
  3. Important role in longevity is "assortative mating."

Fascinated with genealogy, I've started spending too many hours chasing snippets of family stories. I figure if I can learn something about my family tree, it might shed light on my health and how long I will live. I've become obsessed with two ancestors in particular: Permelia Van Valkenburgh and her son Amasa Matoon Van Valkenburgh. Permelia was my great-great-great grandmother. Married at 17 to a distant cousin who shared her last name, she gave birth to 10 children over 18 years and died in 1855 at age 42. Permelia was a 19th-century farm wife in the Catskill Mountains, a place where people didn't roam alone at night for fear of panther attacks. Two of her 10 children died in infancy and one at 20. Her next-to-last child, Amasa, was my great-great grandfather. He was 9 years old when his mother died.

What killed her? If it was childbirth, there is no record of a child born or buried the year she died. If it was flu or tuberculosis or another contagious disease, there is no evidence of anyone else in her family dying in May 1855, although both were common causes of death in 19th-century communities. Maybe it was a laceration that became infected, picked up in unrelenting farm and housework. The month of May in the high Catskills could be chilly, and the winter stores of food would have been nearly depleted. Crops would not yet have produced anything. There was the occasional flash flood in the nearby creeks, so maybe she drowned.

Curious about what killed people in rural New York in the mid-19th century, I found the U.S. Census Mortality Schedules for the state from 1850 to 1880. The United States recorded this information once every 10 years and listed only those who died the year of the survey. Even so, I found some interesting details for Greene County, where she lived, in 1850: consumption (tuberculosis), cholera, dysentery, whooping cough, infection of lungs, infection of hand, infection of brain, asthma, childbirth, drowning and cancer were listed as causes of death. The most frequent cause was cholera. Many times, the named cause of death for people in their 80s and 90s was "old age."

Did any of this have any meaning for me? Probably not. "The big picture is the shift from infectious disease as a major cause of death to chronic diseases," said Charles Rosenberg, professor of history of science at Harvard. Causes of death such as tuberculosis were "background noise," he said, so common that they were unremarkable. What drew more attention were cholera epidemics or influenza sweeping through communities.

Susan Speaker, a historian with the National Library of Medicine at the National Institutes of Health, said that before the 1920s, more Americans died of "microbe-caused diseases" than anything else. The balance started to shift by the 1930s and '40s, she said.

In other words, a farm wife living in the country - while not exposed to the overcrowding and bad water of cities - would have had a number of other health challenges.

For instance, "if you came down with appendicitis in the 1900s in the country, you might be out of luck," said Speaker, "unless you had a local practitioner who was a decent surgeon."

While I was getting closer at making an educated guess at the cause of death, my mother and I ventured into the Catskill Mountains one Sunday morning in August after services at the First Reformed Church in Athens, New York, the village on the Hudson River where we both grew up and where many of our ancestors now rest.

We drove high into the mountains until the ski resorts and gift shops dropped away, the houses became more spread out, and the forests got thicker in the Catskill State Park, land first preserved by the state in 1885. Finally we reached the turnoff to Westkill, the hamlet of a hamlet, tucked between hills in a valley.

The cemetery was small, with maybe 40 stones. The grass had been newly mowed, and damp cuttings thrown by a power mower still plastered the white sides of the Westkill United Methodist Church (built in 1848) and, next to it, the Westkill Baptist Church (built in 1830). One or two graves had collapsed, leaving a deep, grass-lined trench in the earth. We peered inside the churches, but both had been long abandoned. Even the pews were gone.

Back at the far edge of the cemetery, just before the ground dropped off to a creek, I found a dark, mottled headstone. It read:

PERMELIA A.

Wife of

Jacob Van Valkenburgh

Died May 7, 1855

Aged 42 years, 3 mo, 5 ds

Near her was the stone of James, the 20-year-old son who died just two years before her. Along with losing babies Elizabeth, Huldah and George, did James' death in 1853 lead to her decline?

Just a few steps away was her son Amasa, my great-great grandfather.

Amasa M. Van Valkenburgh

Died July 1, 1890

Aged 44 years

Here was another ancestor who died young. Amasa married at age 24, had five children with his wife, Christina Smith, and died in the middle of the summer.

Town records in Lexington, N.Y., eventually turned up his cause of death: "acute peritonitis," which is an inflammation of the abdominal wall. Untreated, as it would have been in pre-antibiotic times, peritonitis leads to sepsis and death. What is still a mystery is what caused the peritonitis. It could have been a puncture wound to the stomach. It also could have been cirrhosis of the liver, which often leads to peritonitis. NIH's Speaker said it would be impossible to know whether the peritonitis resulted from cirrhosis, a perforated gastric ulcer, a burst appendix or a ruptured gall bladder.

Buried alongside him was his wife, Christina. She went on to remarry and outlive a second husband. Christina passed away in 1946 at age 96. She would have remembered the Civil War, World War I, women getting the right to vote and World War II.

Of her five children with Amasa, two lived into their 90s, and another to 87. And her grandson, my grandfather Orrin, lived to 97.

Does this mean, then, that I could count on a longevity gene?

A study published in Genetics shut down that fantasy. Looking at 400 million people born between 1800 and 1920, whose information had been collected from public family trees in Ancestry.com, investigator Graham Ruby found that only about 10 percent of human longevity is inherited. Previous estimates ranged from 15 to 30 percent.

Our intuition is that long life spans run in families, Ruby said. And yes, genetics does contribute to life span, he said, "but to a much lesser extent than we thought."

"Honestly, all of us were a little surprised," said Catherine Ball, chief scientific officer at Ancestry, which collaborated with Ruby at Calico, a California research-and-development company.

"What this work has shown is not that longevity isn't inherited," she said. "It is inherited, but the cause is not often genetics." In other words, humans also inherit money, property and social status, which also influence longevity.

Both Ruby and Ball said that a much more important role in longevity is "assortative mating." In other words, people tend to marry people who are similar to them in location, socioeconomic status and education, and those factors also influence longevity. People are more likely to match the longevity of their in-laws than their ancestors, Ruby said.

The research showed fascinating patterns such as a drop in longevity about 1918, when World War I and the Spanish flu were killing millions, Ball said.

"Over time, the types of things that caused mortality were very different," she said. "Infectious disease was a much more important killer then than now. Childbirth was not something you really wanted to go through."

In other words, both researchers said, much of what foreshadows our longevity today involves healthy lifestyles and access to medical care more than genes. I didn't necessarily uncover any clues about my own health ancestry in my research, but I did develop a greater respect for the enormous achievements of modern medicine.

 

 



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