Infectious Burden: The Cause Of Aging And Age-Related Disease

94 Pages·2016·2.91 MB·English

by  Lustgarten Michael.

Infectious Burden: The Cause of Aging and Age-Related Disease This book
contains the ideas and opinions of its author. It is not in any way a substitute for
the reader’s own physician(s) or other medical professionals based on the
reader’s own individual conditions, symptoms, or concerns. If the reader needs
personal medical, health, dietary, or other assistance or advice, the reader should
consult a competent physician and/or other qualified health professionals. The
author specifically disclaims all responsibility for injury, damage, or loss that the
reader may incur as a direct or indirect consequence of following any directions
or suggestions given in the book.

The unauthorized use and/or duplication of this material without the expressed
and written permission of the author is strictly prohibited.

© 2016 by Michael Lustgarten. All rights reserved.

Cover Image: Scanning election micrograph of methicillin-resistant
Staphylococcus Aureus (yellow) and a dead human neutrophil (red). Source:
National Institute of Allergy and Infectious Diseases.
Introduction
We live in a microbial world. Although there are 7 billion people (7*109) on
earth, in contrast, the total number of prokaryotes (including bacteria) and
viruses have been estimated at 1030 and 1031, respectively (Whitman et al. 1998;
Duerkop et al. 2014). Even without including other microbes (i.e. fungi,
protozoa), we’re outnumbered by at least 1021 to 1! Luckily, all of these
microorganisms aren’t detrimental to human health, but more than 1400
microbial species have been shown to be pathogenic to people (Taylor et al.
2001).
Accordingly, until ~1900, infectious diseases were the major cause of all deaths.
As shown in the figure below, the infectious diseases, pneumonia/ influenza,
tuberculosis, gastrointestinal infections, and diphtheria collectively accounted
for 53% of all deaths (Jones et al. 2012):
As a result, lifespan was short, as people lived an average of only 30 years
(Wiley 2005).
Over the next 100+ years, the establishment of public health departments that
focused on sewage disposal, water treatment, food safety, organized solid waste
disposal, and public education about hygienic practices, and the introduction of
antibiotics and vaccines allowed for a dramatic decrease in infectious disease-
related deaths (http://www.cdc.gov):
In 2010, deaths directly related to infectious diseases (i.e. pneumonia/ influenza)
were only 3% (Jones et al. 2012) of all deaths!
In addition, from 1900-2010, lifespan had its greatest increase in human history,
as most people now live more than 70 years (Wiley 2005). This is the first line
of evidence that links reductions in infectious disease-related mortality with an
increased lifespan.
Because infectious disease-related mortality has been almost completely
eliminated, can we say that the war against infectious disease is over?
Definitely not! Because we are heavily outnumbered by microbes, our existence
is under constant attack. Eventually, our immune system can’t properly handle
this challenge, and very slowly, over time, more and microbes enter and live in
inside us, where they accumulate in various tissues including blood vessels and
the brain, thereby negatively impacting systemic physiology. This increases risk
for most of the primary causes of death, including cardiovascular disease,
cancer, Alzheimer’s disease, cerebrovascular disease, and diabetes. If we live
long enough to escape those diseases, we once again succumb to infectious
disease mortality, as pneumonia is the primary cause of death (other than “old
age”) in adults older than 100 years. In sum, over the past 115+ years, we
haven’t eliminated infectious-related mortality, we have merely delayed it!
Infectious Burden Underlies the Major Causes Of
Death In 2016
Let’s have a look at the data that supports the hypothesis that infection and the
total sum of infectious microbes that live inside us (infectious burden) are
involved with the etiology of the major causes of death in 2016.
Although it has long been thought that the blood is sterile and free of microbes,
recent evidence disputes this hypothesis. In the figure below, we see that bacteria
(measured by the presence of 16S rRNA on the y-axis) are found in whole blood
(light grey bars), and within the sum of white blood cells, red blood cells and
plasma (dark bars) in 29 young, healthy adults (average age, 21 years; Païssé et
al. 2016). On average, each subject had 40 million (4*107) circulating copies of
16S rRNA per milliliter of blood:
Each bacterium has 1 to 15 copies of the 16S gene per genome (Klappenbach et
al. 2001). When considering that our body contains about 5 liters of blood, this
suggests a circulating bacterial load of 13 to 200 billion (low estimate, 4*107
5/0.001 15 = 13.3*109; high estimate, 4*107 5/0.001 = 200109)!
We can also calculate how many circulating white blood cells (WBCs) are
available to counteract this infectious burden. The WBC reference range is
4,000-11,000 cells per microliter of blood. Again, based on a total blood volume
of 5 liters, we have 20 to 55 billion (low end of the range, 4000*5/ 0.000001 =
20*109; high end of the range, 11000*5/ 0.000001 = 55*109) circulating WBCs