The Bright Side of Black Death

April 17, 2015

By Medical Discovery News

Bright Side of Black Death

It’s easy to think that nothing good could come from a disease that killed millions of people. But Dr. Pat Shipman, an anthropologist at Pennsylvania State University, disputed that notion in his recent article in “American Scientist,” where he suggested the Black Death that ravaged Europe in the Middle Ages may have resulted in some positive effects on the human population. Considering that we are in the midst another significant plague (the Ebola virus in West Africa), we could certainly use more information about the role of pandemics on human populations.

The Black Death or Bubonic plague started in the mid-1300s and was caused by a bacterium called Yersinia pestis, which typically enters the body through the bite of a flea. Once inside, the bacterium concentrates in our lymph glands, which swell as the bacteria grow and overwhelm the immune system, and the swollen glands, called buboes, turn black. The bacteria can make their way to the lungs and are then expelled by coughing, which infects others who breathe in the bacteria. The rapid spread of the infection and high mortality rates wiped out whole villages, causing not only death from disease but starvation as crops were not planted or harvested. It killed somewhere between 100 million to 200 million people in Europe alone, which was one-third to one-half of the entire continent’s population at the time. The plague originated in the Far East and spread due to improved trade routes between these two parts of the world.

Today, global travel is easier than ever thanks to extensive international airline networks. Just like with the Black Death, our transportation systems could enhance the spread of a modern plague. Of course, modern healthcare is also more sophisticated and effective, but as the latest Ebola outbreak has reminded us, a pandemic is a realistic possibility.

Dr. Sharon DeWitte, a biological anthropologist at the University of South Carolina, recently made several discoveries from comparing the skeletal remains of those who died from the Black Death and those who died from other causes during the same era. First, she found that older people, who were therefore already frail, died at higher rates. Killing this group at a higher rate created a strong source of natural selection, removing the weakest part of the population.

After the plague years, she found that in general people lived longer. In medieval times, living to 50 was considered old age. But the children and grandchildren of plague survivors lived longer, probably because their predecessors lived long enough to pass on advantageous genes. Today, a genetic variant in European people called the CCR5-D32 allele, which was favored during the natural selection initiated by the plague, is associated with a higher resistance to HIV/AIDS.

Microbes have an intimate relationship with human populations and have shaped human evolution through the ages. We may see survivors of the Ebola virus passing on similarly advantageous genes through natural selection as well.

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Not Smelling Death

April 3, 2015

By Medical Discovery News

Not Smelling Death

This may be Debbie Downer question, but can you guess what condition is most indicative of a person’s imminent demise? It turns out that the strongest predictor of impending death is not cancer, stroke, heart attack, diabetes, or emphysema, but a person’s declining sense of smell.

Scientists at the University of Chicago have revealed that the loss of the sense of smell, officially called olfactory dysfunction, is a significant forecaster of death in older Americans. In this study, 3,005 people aged 57-85 were asked to identify five common scents: peppermint, fish, rose, leather, and orange. Five years later, the health of the same people was evaluated.

As this was an older population, some of the subjects died before the study contacted them again. The surprise was that almost 40 percent of those who died had failed the scent test, identifying only one or none correctly. Anosmia is the technical term for complete loss of the ability to smell, while hyponosmia is the significant (but not total) loss of smell. The mortality rate for those with anosmia was four times higher than for those with normal smell. Those who were hyponosmic had an intermediate mortality compared to normal individuals. So being either anosmic or hyponosmic is associated with an increase in a person’s  mortality. And because of the limited length of this study and the relatively small group examined, the effect on mortality is probably underestimated.

Overall, these results are striking. Since these were older individuals, the possibility of other factors influencing these results was examined. The study ruled out confounding factors such as nutrition, mental health, smoking, alcohol abuse, frailty, and neurodegenerative diseases in the results. Those at a higher risk for anosmia or olfactory loss were males, those who were overweight or obese, and those with a lower socioeconomic status.

While the human sense of smell is not as dominant as in other mammals (such as dogs), it is associated with good health and nutrition. The sense of smell is strongly tied to an array of brain functions and is the strongest sense tied to individual memory. Remembered scents can provoke intense memory responses and can stimulate memories from long ago.

The sense of smell is also highly connected to other parts of the central nervous system. Unique among the senses, normal olfactory function relies on cellular regeneration of the specialized sensory cells lining the inside of the nose. If the olfactory system is not working properly, these cells won’t regenerate like they are supposed to do.

Recently, we reported on a study that determined that human noses are capable of distinguishing between at least a trillion different scents. It now appears that the loss of this ability is an omen of death. The exciting part is that a simple scent test taking less than five minutes could become a powerful new way to identify those at high risk of upcoming mortality and lead to interventions that could prolong people’s lives.

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