Work the Night Shift? Beware Diabetes
An Upset in the Body's Internal Clock May Cause Blood Sugar Spikes, Insulin Resistance
March 3, 2009 -- By pitting the time clock against the body's internal
clock, night-shift work may cause
diabetes and obesity.
The 8.6 million Americans who work the night shift are at increased risk of
obesity, diabetes, and heart disease. Why?
A new study shows that much of the body's biological clock -- its circadian
rhythm -- keeps day-shift time even when a person goes on the night shift.
Harvard/Brigham and Women's Hospital researcher Frank A.J.L. Scheer and
colleagues studied five women and five men who volunteered to undergo a kind of
progressive jet lag.
For eight "days," the participants ate and slept on a 28-hour
schedule, during which they ate four identical-calorie meals.
When their cycle shifted about 12 hours out of phase -- when they were
sleeping during the day and up at night -- the participants' bodies got
seriously out of rhythm:
- After meals, three of eight participants tested had blood sugar spikes and
insulin resistance similar to those seen in people with diabetes or prediabetes.
- The participants' bodies made more insulin, yet their blood sugar went
- Blood levels of leptin went down. Long term, this would increase obesity
risk, as decreased leptin makes people burn less energy while craving more
- Sleep efficiency -- the time one
actually sleeps while in bed -- decreased.
pressure got higher.
- Cortisol -- the so-called stress hormone that affects
blood pressure and blood sugar -- rose and dropped at the wrong time.
The study participants went back to their normal sleep schedules after the
experiment. That's not an option for shift workers. Long term, the changes seen
in the Scheer study may have ominous consequences.
Animals studies, the researchers note, show that "internal
desynchronization" from repeated shifts in the day/night cycle cause
Scheer and colleagues report their findings in the March 2 early online
edition of the Proceedings of the National Academy of Sciences.