Your Night Light Color may Affect Your Mood

In a study involving hamsters, researchers found that blue light had the worst effects on mood-related measures, followed closely by white light.

But hamsters exposed to red light at night had significantly less evidence of depressive-like symptoms and changes in the brain linked to depression, compared to those that experienced blue or white light.

The only hamsters that fared better than those exposed to red light were those that had total darkness at night.

The findings may have important implications for humans, particularly those whose work on night shifts makes them susceptible to mood disorders, said Randy Nelson, co-author of the study and professor of neuroscience and psychology at The Ohio State University.

"Our findings suggest that if we could use red light when appropriate for night-shift workers, it may not have some of the negative effects on their health that white light does," Nelson said.

The study appears in the Aug. 7, 2013, issue of The Journal of Neuroscience.

The research examined the role of specialized photosensitive cells in the retina -- called ipRGCs -- that don't have a major role in vision, but detect light and send messages to a part of the brain that helps regulate the body's circadian clock. This is the body's master clock that helps determine when people feel sleepy and awake.

Other research suggests these light-sensitive cells also send messages to parts of the brain that play a role in mood and emotion.

"Light at night may result in parts of the brain regulating mood receiving signals during times of the day when they shouldn't," said co-author Tracy Bedrosian, a former graduate student at Ohio State who is now a postdoctoral researcher at the Salk Institute. "This may be why light at night seems to be linked to depression in some people."

What people experience as different colors of light are actually lights of different wavelengths. The ipRGCs don't appear to react to light of different wavelengths in the same way.

"These cells are most sensitive to blue wavelengths and least sensitive to red wavelengths," Nelson said. "We wanted to see how exposure to these different color wavelengths affected the hamsters."

In one experiment, the researchers exposed adult female Siberian hamsters to four weeks each of nighttime conditions with no light, dim red light, dim white light (similar to that found in normal light bulbs) or dim blue light.

They then did several tests with the hamsters that are used to check for depressive-like symptoms. For example, if the hamsters drink less-than-normal amounts of sugar water -- a treat they normally enjoy -- that is seen as evidence of a mood problem.

Results showed that hamsters that were kept in the dark at night drank the most sugar water, followed closely by those exposed to red light. Those that lived with dim white or blue light at night drank significantly less of the sugar water than the others.

After the testing, the researchers then examined the hippocampus regions of the brains of the hamsters.

Hamsters that spent the night in dim blue or white light had a significantly reduced density of dendritic spines compared to those that lived in total darkness or that were exposed to only red light. Dendritic spines are hairlike growths on brain cells that are used to send chemical messages from one cell to another.

A lowered density of these dendritic spines has been linked to depression, Nelson said.

"The behavior tests and changes in brain structure in hamsters both suggest that the color of lights may play a key role in mood," he said.

"In nearly every measure we had, hamsters exposed to blue light were the worst off, followed by those exposed to white light," he said. "While total darkness was best, red light was not nearly as bad as the other wavelengths we studied."

Nelson and Bedrosian said they believe these results may be applicable to humans.

In addition to shift workers, others may benefit from limiting their light at night from computers, televisions and other electronic devices, they said. And, if light is needed, the color may matter.

"If you need a night light in the bathroom or bedroom, it may be better to have one that gives off red light rather than white light," Bedrosian said.

Source-Eurekalert

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Study Sheds Light on Smoking Cessation, Weight Gain, and Subsequent Heart Disease Risk

"Cigarette smoking is an important cause of cardiovascular disease, and smoking cessation reduces the risk. However, weight gain after smoking cessation may increase the risk of diabetes and weaken the benefit of quitting," write Juhua Luo, Ph.D., of the Indiana University School of Public Health, Bloomington, Ind., and colleagues.

As reported in a Research Letter, the authors used data from the Women's Health Initiative (WHI) to assess the association between smoking cessation, weight gain, and subsequent coronary heart disease (CHD) risk among postmenopausal women with and without diabetes. In the WHI, 161,808 postmenopausal women 50 through 79 years of age were recruited from 40 sites between 1993 and 1998 and followed up every 6 to 12 months. Women without known cancer or cardiovascular disease at baseline or CHD at year 3 were followed up until CHD diagnosis, date of death, loss to follow-up, or September 30, 2010, whichever occurred first.

Of 104,391 women followed up, 3,381 developed CHD, during an average of 8.8 years. The researchers found that smoking cessation was associated with a lower risk of CHD among postmenopausal women with and without diabetes. Weight gain following smoking cessation weakened this association, especially for women with diabetes who gained 11 lbs. or more, although power was limited in this subgroup due to the small number of cases.

Source-Eurekalert

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Latest Setback Sheds Light on 'Gap' for HIV Vaccine Efforts

With the next attempts expected to be years away, top researchers now say there is a "void" or a "gap" in current clinical trial efforts to test whether a vaccine may be safe and effective in people.

A kind of ongoing autopsy of the last four major bids to make an HIV vaccine has informed the field as to what does not work, with the latest casualty being a trial called HVTN 505 that was halted early because it did not prevent HIV.

"It leaves us with a gap in several years before we have another HIV vaccine efficacy trial under way, and that is unfortunate," said James Kublin, executive director of the HIV Vaccine Trials Network.

Another concern for researchers is that two vaccine trials -- HVTN 505 and a previous trial known as STEP that ended unsuccessfully in 2007 -- both revealed apparent increases in the number of vaccinated patients who got HIV.

HVTN 505 showed 41 cases of HIV were acquired in the vaccine group, compared to 31 in the placebo group. Among some 2,500 participants, the difference was not statistically significant, and so researchers found that no harm was caused by the trial.

"But the number is in the wrong direction," said trial leader Scott Hammer, who described the trial's outcome as a "disappointment."

Researchers are still investigating why this may have happened, but some theorize the cold virus known as Ad5 that served as a vector to deliver the vaccine may have somehow caused more infections by making it easier for HIV to penetrate the body.

"You scratch your head," said Hammer, a professor of medicine at Columbia University, adding that Ad5 may now be considered too risky and other options are being investigated.

"No one is going to want to a do a major trial with this sort of vector in the future," he told AFP.

The key puzzle in the vaccine search has been the nature of the human immunodeficiency virus itself, which has managed to fool modern medicine by changing its genetic makeup so often that a single weapon cannot silence it.

"The virus is a very elusive foe," said Wayne Koff, chief scientific officer at the International AIDS Vaccine Initiative (IAVI).

"It is more variable than almost any other virus that a vaccine has been attempted for. So if one wants to make antibodies against a virus that is variable, one has to have a broadly reactive antibody," he told AFP.

A small number of HIV-positive people have been found to produce antibodies that can neutralize a broad range of HIV variants, but scientists have not yet figured out how to make a vaccine from that information.

"Lots of people are working on that very hard. I would have thought we would have that immunogen to test in phase I trials by now, but hopefully soon," said Hammer, a leading HIV researcher.

About 34 million people are infected with HIV worldwide, and AIDS has killed 30 million people since the epidemic began 30 years ago.

The vaccine field has fallen short of expectations since 1984, when Margaret Heckler, who was then US secretary of Health and Human Services, declared a vaccine would be ready for testing in about two years' time.

The first phase I trial of a vaccine began in 1987 at the National Institutes of Health in Bethesda, Maryland, and included 138 healthy volunteers. The first large-scale trials did not begin until the late 1990s.

The sole success story to date has been a trial in Thailand known as RV144, which in 2009 saw a modest, 31 percent rate of protection, still far below the 50 percent threshold needed in order to license a vaccine.

Researchers are continuing to study the results for clues as to why it worked in some cases but not others, and why it appears the protective effects may have waned over time.

A similar vaccine modeled for South Africans is expected to enter human trials in the next couple of years. Other approaches for increasing T-cell immunity are also on the horizon.

"I am an optimist. I think we are at least halfway there, hopefully further," said Hammer. "The world needs an HIV vaccine."

Source-AFP

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