In the news yesterday, a new study showing how shift work (night time work outside of normal daytime hours) doubles a teen's risk of developing Multiple Sclerosis.  This is considered an "environmental factor" as opposed to a genetic factor.  This new paper comes from the Karolinska Institute in Sweden and was published in the Annals of Neurology.  The researchers did not propose a specific theory as to how shift work might increase the risk of MS, but they did comment on how circadian rhythm disruption might affect melatonin and the immune system.

Here is the complete paper:

http://sverigesradio.se/diverse/appdata/isidor/files/83/11395.pdf

Oddly enough, just last week, another published study showed how shift work raises the risk of metabolic disease, higher body mass index (BMI) and cardiac problems in young adults vias cortisol release. This study was undertaken by Dutch researchers and published in the Journal of Clinical Endocrinology-- only a week prior to the Swedish study.  

Here's the abstract for that paper on shift work:

http://jcem.endojournals.org/content/early/2011/08/25/jc.2011-1551.abstract

Shift work, or work outside standard daytime hours, has been associated with an increased incidence of metabolic syndrome, and cortisol plays a major role in the development of the disease.

Manenschijn and colleagues looked at normal cortisol in shift workers versus day workers by measuing levels of this stress hormone in scalp hair.  One centimeter of hair represented a period of about one month.  They also speculated that higher BMI correlated to long-term cortisol levels.

The researchers also found was that this cortisol increase was the highest and had the most negative affect on the younger participants in the study, via an increase in their higher BMI rates.

Ther authors suggested that older shift workers suffered from less stress than their younger colleagues or simply adjusted better to unconventional hours.  Also, sleep patterns and circadian rhythms change as people grow older, which may have muted the impact of shift work on cortisol levels in older people.

Cortisol is a known endothelial disrupter and can create hypertension and cardiovascular problems as well as metabolic disease.  This is why stress is a known factor in heart disease.

We also already know a few environmental risk factors for young people in developing MS-

SMOKING-  Here's the John's Hopkins study showing how teen smoking increased the risk of developing MS by 2.7 times

http://www.hopkinsmedicine.org/gim/news/2009_News_Items/3-3-09.html

OBESITY and HIGER BMI--The Nurses' Health Study showed this doubled the risk of teen girls later developing MS

http://www.sciencedaily.com/releases/2009/11/091109173400.htm

And now, we can add shift work to the list of environmental factors in teens, and perhaps cortisol increases in the young.  What is interesting is to note that each of these environmental factors affects the vasculature, via endothelial disfunction.  Each of these risks is linked to vasoconstriction and impaired blood flow.  If one can step away from the autoimmune theory of MS and see the disease from the perspective of Dr. Zamboni's research (or that of Rindfleisch, Putnam, Fog and Swank) it makes sense.

Let's hope these researchers read each others' work, and look at cortisol, BMI and blood flow in MS.

Joan