Statistics Predicted a Healthier Medieval London Following the Black Death

Black_Death

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

Image 2: pone.0096513

Image 3: pone.0096513

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Science for Marathon Monday

Update: On Monday afternoon at 2:56pm, two explosions occurred near the finish line of the Boston Marathon. In light of these events, PLOS ONE would like to express our deepest sympathies for the victims and families affected by this tragedy.

 

Still procrastinating on those tax returns? If you have finally filed and are looking to blow off some steam, maybe a 26.2 mile run will do the trick! Today on April 15th, over 27 thousand people will lace up their sneakers, warm up their muscles and prepare for one of the world’s oldest races, the Boston Marathon.

Vasque Mindbenders after a muddy trail run in the hills of Griffith Park.  (c) 2011 Geoff CordnerThe very first Boston Marathon was held in 1897 and was then known as the B.A.A. Road Race. Originally 24.5 miles in length, the race was extended to 26.2 miles in 1924 to conform to the Olympic standard. Since that first race day which featured 15 runners, the marathon has grown immensely, with 26 thousand people participating last year.

In honor of the 117th marathon or whatever race you may be running today, here are some recently published articles featuring the sport:

In a paper published this February, researchers have determined the cause of runners fatigue during a marathon in warm weather. These authors recruited 40 amateur runners to test their fatigue and measure their pace during the race. Through their analysis, the authors found that participants who felt the greatest fatigue had elevated levels of blood markers of muscle breakdown. There is still further research to be done to find if this muscle damage is due to mechanistic or metabolic factors.

But what effect does warm weather have on a marathon? In another recent article, authors investigated whether climate change has affected the winning times of the Boston Marathon.  The authors found the temperatures between 1933 and 2004 did not consistently slow winning times on race day. However, the analysis also indicated that if temperatures warmed by 0.058°C a year, we would have a 95% chance of detecting a slowing of winning marathon times by 2100. And if average race day temperatures had warmed by 0.028°C a year (a mid-range estimate) we would have a 64% chance of detecting a decline in winning timings by 2100.

This analysis gives us some insight on how running may change in the future, but have you ever wondered what the sport was like 30,000 years ago? Unlike current shoe wearing athletes, our ancestors were barefoot runners and so are other modern human populations, including the Daasanach. In an article published this year, researchers have investigated the foot strike patterns among barefoot runners in northern Kenya. Data was collected from 38 adults, who ran at their own speed and distance. The authors found that not all the barefoot runners landed on their fore- or mid foot, but the majority landed on their heels first. This observation dismisses the original hypothesis that the barefoot runners would land on the fore-or mid foot, and suggests that there may be a number of other factors which influence foot strike patterns.

Whether you are ready to take your mark, or getting set to file those taxes, visit our site here for more papers on the topic.

 

Citations:

Citation: Del Coso J, Fernández D, Abián-Vicen J, Salinero JJ, González-Millán C, et al. (2013) Running Pace Decrease during a Marathon Is Positively Related to Blood Markers of Muscle Damage. PLoS ONE 8(2): e57602. doi:10.1371/journal.pone.0057602

Citation: Miller-Rushing AJ, Primack RB, Phillips N, Kaufmann RK (2012) Effects of Warming Temperatures on Winning Times in the Boston Marathon. PLoS ONE 7(9): e43579. doi:10.1371/journal.pone.0043579

Citation: Hatala KG, Dingwall HL, Wunderlich RE, Richmond BG (2013) Variation in Foot Strike Patterns during Running among Habitually Barefoot Populations. PLoS ONE 8(1): e52548. doi:10.1371/journal.pone.0052548

Image: on Flickr by geoff cordner

Heart Health Awareness Month

Before this month comes to a close, let us not forget to honor February as American Heart Month.

According to the CDC, heart disease, also known as coronary artery disease or cardiovascular disease,  claims 600,000 lives in the U.S. each year. Heart disease refers to the plaque buildup in the walls of the arteries, resulting in a heart attack or stroke. Other heart conditions include arrhythmia, congenital defects, heart failure and hypertension (high blood pressure).

Researchers continue to study the best ways to properly care for and treat the beating organ within us. Last September, we discussed cardiovascular heath among women, and highlighted related articles published. Today, in honor of American Heart Month, we bring you recently published research that increases awareness and insight to heart health.

Did you ever feel there was a connection between your heart beat and self-image? PLOS ONE authors have attempted to answer this question by investigating the relationship between self-objectification and the beating heart in a recent article. Using a heartbeat perception task and questionnaire, researchers found that women who were able to hear their own heart beat were less likely to objectify themselves, proving yet another link between heart health and overall wellbeing.

In another recently published study, researchers explored the connection between white blood cell count and heart disease risk in young adults. The authors tested the white blood cell counts for over 29,000 healthy young men over an average of seven and a half years and also screened the participants for signs of coronary artery disease. Their investigation found that a higher white blood cell count correlated with coronary artery disease risk in young men. They concluded that white blood cell count may help in identifying young men with low or high risk for heart disease progression.

In a third article published by PLOS ONE, researchers from the University of Granada investigated heart rate variability and cognitive performance. Participants were divided into a high-fit group and a low-fit group, and the authors measured the effects of three cognitive tasks on the participant’s heart rate variability. The researchers found that cognitive processing has an effect on heart rate variability, and the main benefit of fitness level was associated with processes involving sustained attention.

These articles are just a taste of the PLOS ONE research into cardiovascular health and the prevention of heart disease. As American Heart Month comes to an end, explore more research on the topic here.

Citations:

Ainley V, Tsakiris M (2013) Body Conscious? Interoceptive Awareness, Measured by Heartbeat Perception, Is Negatively Correlated with Self-Objectification. PLoS ONE 8(2): e55568. doi:10.1371/journal.pone.0055568

 Twig G, Afek A, Shamiss A, Derazne E, Tzur D, et al. (2012) White Blood Cell Count and the Risk for Coronary Artery Disease in Young Adults. PLoS ONE 7(10): e47183. doi:10.1371/journal.pone.0047183

 Luque-Casado A, Zabala M, Morales E, Mateo-March M, Sanabria D (2013) Cognitive Performance and Heart Rate Variability: The Influence of Fitness Level. PLoS ONE 8(2): e56935. doi:10.1371/journal.pone.0056935

Image Credit: natalie419 on Flickr

Announcing: Women’s Health and Fitness Series

This month, in honor of National Women’s Health and Fitness Day on September 26th, we’ll be exploring upcoming and previously published work in PLOS ONE surrounding this topic. The breadth of this subject is wide and, sure, we could probably start a whole new blog just to discuss PLOS ONE articles about women’s health, but instead we’ve created a bite-sized series that will highlight a few important issues, including cardiovascular health, anorexia, pregnancy, and ovarian cancer.

We know that physical fitness has significant repercussions for overall physical and mental well-being, and the results of a clinical trial  published in PLOS ONE earlier this year further underscore how physical activity relates to other health issues. The study, led by researchers from Pennington Biomedical Research Center in Baton Rouge, Louisiana showed that for overweight women, 6 months of aerobic exercise reduced total counts of white blood cells and neutrophils, two markers commonly associated with an increased risk of coronary heart disease and death.

The researchers monitored 390 participants, who alternated between sessions of walking on a treadmill and riding a recumbent bike. One group acted as a control, and the other three groups were prescribed specific exercise “dosages.” The study showed that any increase in exercise improved the participants’ white blood cell and neutrophil counts, and that the effects were generally dose-dependent, with increased exercise resulting in increased health benefit returns.

The study was part of a broader trial called “The Dose-Response to Exercise in Women Aged 45–75 yr” (DREW) study. The most compelling part of this research was that the doses of exercise were strictly monitored in a lab, which led to adherence by the subjects and produced high-quality results.

PLoS ONE 7(2): e31319. Table 2: Mean (95%CI) change in anthropometric and fitness data and total WBC and WBC subfraction counts after 6 months of intervention.

Lack of aerobic exercise may also contribute to the ever-increasing prevalence of Type 2 diabetes found in Americans. The CDC estimates that 26 million Americans have diabetes, half of them women, and it is the 7th leading cause of death in the United States. 90-95% of all diagnosed cases of diabetes are Type 2 diabetes, which is developed by adults late in life and is often a result of obesity and other environmental factors. (Type 1 is more commonly found in children born without the ability to produce insulin.)

There may also be a correlation between socioeconomic status and the incidence of Type 2 diabetes, as explored in a clinical trial  published in December 2011. Researchers from Brigham and Women’s Hospital in Boston observed 23,992 women between February 1993 and March 2007 and found that during this period, 1,262 women developed Type 2 diabetes. Lower socioeconomic status was associated with increased diabetes risk in these women, and this correlation was largely explained by behavior, particularly increased weight.

These two studies only offer a small sample of the extensive research published in this field, both in PLOS ONE and elsewhere, but nonetheless provide compelling evidence that it’s important to get out there and get active.  I look forward to sharing more examples over the next month, so stay tuned!

Citation: Johannsen NM, Swift DL, Johnson WD, Dixit VD, Earnest CP, et al. (2012) Effect of Different Doses of Aerobic Exercise on Total White Blood Cell (WBC) and WBC Subfraction Number in Postmenopausal Women: Results from DREW. PLoS ONE 7(2): e31319. doi:10.1371/journal.pone.0031319

Citation: Lee TC, Glynn RJ, Peña JM, Paynter NP, Conen D, et al. (2011) Socioeconomic Status and Incident Type 2 Diabetes Mellitus: Data from the Women’s Health Study. PLoS ONE 6(12): e27670. doi:10.1371/journal.pone.0027670

Photo Credit: Lululemonathletica w/CC-by License