Statistics Predicted a Healthier Medieval London Following the Black Death

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The Black Death, a pandemic at its height in Europe during the mid-14th century, was a virulent killer. It was so effective that it wiped out approximately one third of Europe’s population. Recent studies have shown that the elderly and the sick were most susceptible. But was the Black Death a “smart” killer?

A recent PLOS ONE study indicates that the Black Death’s virulence might have affected genetic variation in the surviving human population by reducing frailty, resulting in less virulent subsequent outbreaks of the plague. By examining the differences in survival rates and mortality risks in both pre-Black Death and post-Black Death samples of a London population—in combination with other, extrinsic factors, like differences in diet between the two groups—the researcher found that in London, on average, people lived longer following the plague than they did before it, despite repeated plague outbreaks. In other words, in terms of genetic variation, the Black Death positively affected the health of the surviving population.

To uncover differences in the health of medieval Londoners, Dr. Sharon DeWitte of the University of South Carolina examined 464 pre-Black Death individuals from three cemeteries and 133 post-Black Death individuals from one. She chose a diverse range of samples for a comprehensive view of the population, including both the rich and the poor, and women and children, but targeted one geographic location: London.

The ages-at-death of the samples were determined by calculating best estimates—in statistics these are called point estimates—based on particular indicators of age found on the skeletons’ hip and skull bones. Individuals’ ages were then evaluated against those in the Anthropological Database of Odense University, a pre-existing database comprising the Smithsonian’s Terry Collection and prior age-at-death data from 17th-century Danish parish records.

After estimating how old these individuals were when they died and comparing the age indicators against the Odense reference tool, the author conducted statistical analyses on the data to examine what the ages-at-death could tell us about the proportion of pre- and post- Black Death medieval Londoners who lived to a ripe old age, as well as the likelihood of death.

Survivorship was estimated using the Kaplan-Meier Estimator, a function used to indicate a quantity based on known data; in this case the function evaluated how long people lived in a given time period (pre-Black Death or post-Black Death). The calculated differences were significant: In particular, the proportion of adults who lived beyond the age of 50 from the post-Black Death group was much greater than those from the pre-Black Death group.

Age-at-death Distributions

Age-at-death Distributions

In the pre-Black Death group, death was most likely to occur between the ages of 10 and 19, as seen above.

The Kaplan-Meier survival plot shows how the chances of survival, which decrease with age, differ for Pre-Black Death and Post-Black Death groups, as seen below.

Survival Functions

Survival Functions

As the survival plot indicates, post-Black Death Londoners lived longer than there Pre-Black Death predecessors.

Finally, Dr. DeWitte estimated the risk of mortality by applying the age data to the statistical model known as the Gompertz hazard, which shows the typical pattern of increased risk in mortality with age. She found that overall post-Black Death Londoners faced lower risks of mortality than their pre-Black Death counterparts.

To make long and complicated methodology short, these analyses indicate that post-Black Death Londoners appear to have lived longer than pre-Black Death Londoners. The author estimates that the general population of London enjoyed a period of about 200 years of improved survivorship, based on these results.

The virulent killer, the Black Death, may have helped select for a healthier London by influencing genetic variation, at least in the short term. However, to better understand the improved quality of life of post-Black Death London, the author suggests further study to disentangle two major factors: the selectivity of the Black Death, coupled with improvements in lifestyle for post-Black Death individuals. For example, the massive depopulation in Europe resulted in increased wages for workers and improvements to diet following the plague, which also likely improved health for medieval Londoners. By unraveling intrinsic, biological changes in genetic variation from outside extrinsic factors like improvements in diet, it may be possible to better understand the aftermath of one of the most devastating killers in infectious disease history.

The EveryONE blog has more on the medieval killer here.

Citation: DeWitte SN (2014) Mortality Risk and Survival in the Aftermath of the Medieval Black Death. PLoS ONE 9(5): e96513. doi:10.1371/journal.pone.0096513

Image 1: The Black Death from Simple Wikipedia

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A Disease of Considerable Antiquity: Cancer Detected in a Nubian Skeleton

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Cancer, the transformation of normal cells into malignant tumor cells, reigns among diseases as one of the leading causes of death around the world. In 2012, cancer claimed 8.2 million lives, and numbers continue to increase each year. While our understanding of cancer is far from complete, we’ve been able to attribute some of the killer’s virulence to increased environmental risk: Increased pollutants and other environmental carcinogens, coupled with an average increase in tobacco and alcohol use and added to a concurrent decrease in daily exercise, cumulatively represent significant risk factors directly related to an increasingly modern world. Ironically, we humans also live a lot longer than we used to, which increases the disease’s chances of occurring.

However, we have identified far fewer examples of the disease in the archaeological record compared to its current frequency in the current population, which has led to the idea that cancer was much less widespread in antiquity. As a result, very little is known about its evolutionary history.

As part of a larger research project undertaken by the British Museum in the city of Amara West, Sudan, the authors of a PLOS ONE paper dug a little deeper into the dark, early history of cancer. Their subject of interest was an over 3,000 year-old skeleton of a young man from ancient Nubia, then part of Egypt, whose remains were excavated at this site, designated on the map below.

Figure 1

When the researchers uncovered skeleton 244-8, as he has been cataloged, they were presented with the difficulties of examining a less-than-complete body. Parts of the skeleton had been broken, highlighted as fragmentary in the image below. In addition, salt in the surrounding soil had slowly damaged the skull over time. The soft tissue of the over 3,000-year-old skeleton, was also long gone.

Figure 3

On top of these difficulties, damages to the body incurred over time, both before and after death, can look very similar to the eye. Cancer, in particular, is notoriously hard to diagnose in human remains; its similarities to other pathologies combined with natural damages sustained after burial made the researchers’ task of properly diagnosing skeleton 244-8 a complicated one. The earliest signs of cancer in bone are also only visible via methods like X-ray that allow us to visualize the inner parts of bone where the disease begins, which the naked eye cannot see.

The researchers assessed the condition of skeleton 244-8, using digital microscopes, scanning electron microscopes (SEM), and radiography (X-rays), and by examining the visual markers on the bone. They looked for evidence of sustained lesions, or damage on the bone, which they found on his vertebrae, ribs, sternum, pelvis, and other parts of the skeleton.

Figure 8

In the X-ray and photo image above of a rib, we can see the damage as noted by the arrows. The parts of the skeleton most affected by lesions were sections of the spine. The image below depicts an especially damaged thoracic vertebra.

Figure 9

The authors discussed four possible causes for the skeleton’s bone damage:

  • Metastatic organ cancer, or the rapid creation of abnormal cells that spread from the original site in the organs to other parts of the body
  • Multiple myeloma, a cancer of the plasma cells in bone marrow
  • Fungal infection
  • Taphonomic damage, or natural decay after death

Although very similar, the visual markers on bone differ slightly depending on the malady causing the damage. We can see in the image below of the tibia that taphonomic damage caused by insects is slightly more uniform in shape than lesions caused by cancer, and the holes continue straight through to the other side of the affected bone.

Figure 13

Based on the shape, size, and appearance of the lesions under X-ray, the authors surmised that the man suffered from metastatic cancer, originating in the man’s organs. However, since no soft tissue was preserved over time, it is nearly impossible to ascertain the exact location of skeleton 244-8’s primary tumor, which would have affected soft tissue like his organs.

Considering the decay caused by time, salt, and insects, the researchers were able to ascertain quite a lot about skeleton 244-8 based on their examinations of the skeleton. In addition to diagnosing him with metastatic cancer, researchers suggest that skeleton 244-8 was a young man between the ages of 25 to 35 who belonged to a middle-class Nubian family at the time of his death, based on the context of his burial.

With increasing advances in the technology used to examine subjects like skeleton 244-8, the inner secrets and pathologies held in places like the inside of bone become less of a mystery. With further study, we’ll be able to understand a little more about the environmental risk factors of skeleton 244-8’s own world: for instance, the possible use of fires in poorly ventilated mudbrick houses, or possible infectious diseases spread by parasites. By taking a closer look at human remains like skeleton 244-8, it may eventually be possible to see the effects of a disease not only of our time, but of considerable antiquity.

Citation: Binder M, Roberts C, Spencer N, Antoine D, Cartwright C (2014) On the Antiquity of Cancer: Evidence for Metastatic Carcinoma in a Young Man from Ancient Nubia (c. 1200BC). PLoS ONE 9(3): e90924. doi:10.1371/journal.pone.0090924

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Picked Clean: Neanderthals’ Use of Toothpicks to Fight Toothache

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The toothpick —an often unnoticed tool for post-meal rituals and appetizer stability—has played a greater role in our ancestors’ health and comfort than many would imagine. In a world before dentists, Neanderthals and modern humans took oral hygiene into their own hands using the only tools they had readily available: little bits of nature they found surrounding them.

Researchers from Spain have presented evidence in PLOS ONE that Neanderthals used small sticks or blades of grass not only to remove fragments of food from between their teeth, but also to lessen the pain caused by periodontal disease, a form of gum disease. While multiple human and Neanderthal remains have been found showing evidence of toothpick use, the authors propose that the combined evidence of toothpick use and gum disease suggests that Neanderthals were perhaps practicing an early form of dental care.

The samples in the image above show an adult’s upper jaw with three teeth left intact found at the Cova Foradà cave site in Valencia, Spain, amidst animal remains and tools dated to the Mousterian era (300,000-30,000 years ago). The adult teeth, believed to belong to an individual between 35-45 years old, show heavy wear on the top surface and exposed roots, the result of a lifetime’s consumption of fibrous and abrasive foods like meats and grains. There are no signs of cavities in the remaining teeth, though decayed bone and the porous surface texture of the left side of the jaw indicate the presence of gum disease.

Two distinct grooves are present on the sides of the existing premolar and molar above the crown of the tooth. These grooves were caused by consistent dragging of a tool across the side of the tooth. The existence of these marks above the gum line indicates heavy dental wear and disease. Here, the gums had receded and left the base of the tooth unprotected. With the roots exposed, it would be easy for leftover debris from meals to get stuck and put pressure on already inflamed gums. The use of a foreign object pushed between the teeth would remove any particles lodged in this sensitive area. Without the extra burden of invasive food detritus, force on the gums would be reduced and irritation and pain would decrease.

Over the last few years, studies have shown that Neanderthals were capable of complex behaviors and emotions, may have used a sophisticated language, were more often right-handed than left, and were generally not the inferior cousins some thought they were. As this study shows, they practiced dental care as well. So, the next time you’re heading out of your favorite restaurant, take a good look at that bowl of toothpicks at the front: the contents could very well be evidence of one of our oldest habits.

Check out more coverage of this article in National Geographic and Archaeology magazine.

Citation: Lozano M, Subirà ME, Aparicio J, Lorenzo C, Gómez-Merino G (2013) Toothpicking and Periodontal Disease in a Neanderthal Specimen from Cova Foradà Site (Valencia, Spain). PLOS ONE 8(10): e76852. doi:10.1371/journal.pone.0076852

Image Credit: Image from Figure 2 of the manuscript

Exploring multiple facets of modern men’s health

2695540485_7fed1903e5_zJune is Men’s Health Month! This is a time to bring awareness to preventable health issues and encourage early detection of diseases affecting men. As we wind down from celebrating Father’s Day this past weekend, here are a few articles focusing on some important men’s health issues.

Lowering salt intake helps alleviate a number of health concerns, such as decreasing the risk of heart disease, stroke and stomach cancer. However, how easy is it to reduce your sodium intake without compromising taste, or your wallet?  In a recent study, researchers sought to determine how feasible a low-sodium, inexpensive and nutritious meal for men could be. The authors used cost and nutritional data to model and optimize familiar diets. In this analysis, they showed that it is possible to decrease sodium levels to well below the recommended maximum, proving that nutrition does not need to be compromised when preparing an enjoyable low-cost meal.

So what should men be consuming to help with disease prevention? Olive plant leaves (Olea europaea L.) have been used in traditional medicine to treat diabetes for centuries. In a PLOS ONE clinical trial published this year, researchers investigated the effects of olive polyphenols on insulin balance.  In this study, 46 male participants received either capsules of olive leaf extract or a placebo for 12 weeks.  Through their observations, the researchers found that olive leaf extract significantly improved two factors related to Type 2 Diabetes (insulin sensitivity and pancreatic ?-cell secretory capacity) in overweight, middle-aged men.

What about prostate health, you might ask? The Prostate Specific Antigen test, along with digital rectal examination is widely used for prostate cancer screening. PSA, which stands for Prostate Specific Antigen, is a glycoprotein secreted by epithelial cells of the prostate gland, and individuals with prostate cancer have a higher than normal amount of this compound in their systems. PSA levels can also change in response to external factors like surgery, though, so understanding these other forces is crucial for the test to be effective.  In a recent study, authors investigated whether bike riding affects PSA concentration in men. The researchers took blood samples from 129 male participants 60 minutes before a bike ride and 5 minutes after completion. They found that cycling caused their PSA to increase an average of 9.5% when measured within 5 minutes after completing the ride. Based on these findings, the authors suggest a 24–48 hour period of abstinence from cycling before a PSA test to avoid any false positive results.

These articles are just a taste of the published articles touching on men’s health; for more research visit PLOS ONE here.

 

Citations:

Wilson N, Nghiem N, Foster RH (2013) The Feasibility of Achieving Low-Sodium Intake in Diets That Are Also Nutritious, Low-Cost, and Have Familiar Meal Components. PLoS ONE 8(3): e58539. doi:10.1371/journal.pone.0058539

de Bock M, Derraik JGB, Brennan CM, Biggs JB, Morgan PE, et al. (2013) Olive (Olea europaea L.) Leaf Polyphenols Improve Insulin Sensitivity in Middle-Aged Overweight Men: A Randomized, Placebo-Controlled, Crossover Trial. PLoS ONE 8(3): e57622. doi:10.1371/journal.pone.0057622

Mejak SL, Bayliss J, Hanks SD (2013) Long Distance Bicycle Riding Causes Prostate-Specific Antigen to Increase in Men Aged 50 Years and Over. PLoS ONE 8(2): e56030. doi:10.1371/journal.pone.0056030

 Image Credit: on Flickr by Lindz Graham