5 studies you may have missed

Here's a roundup of five medical studies published this week that might give you new insights into your health, mind and body. Remember, correlation is not causation – so if a study finds a connection between two things, it doesn't mean that one causes the other.

Sunlight may lower blood pressure
Journal: Journal of Investigative Dermatology

Going outside and embracing the sun may come with unexpected health benefits, a new study suggests. But don't get so much direct exposure that you risk skin cancer.

Researchers looked at the benefits of radiation from the sun. Volunteers received a dose of ultraviolet-A radiation in a laboratory that was equivalent to being in the sun for 30 minutes in summertime in Southern Europe.

The study authors found that participants' blood pressure decreased, but they're not exactly sure why. It's possible that sunlight mobilizes molecules derived from nitric oxide, "so they travel from skin to blood, where they dilate blood vessels and lower blood pressure," LiveScience reports.

Study authors don't know whether blood pressure would continue dropping with multiple exposures to UVA, or if a person's age, sex or disease would affect the result.

Read more from LiveScience

Oldest-known living cancer is '11,000 years old'
Journal: Science

Scientists have decoded the genome of a rare sexually-transmitted cancer that's 11,000 years old. It began in one dog and has been spreading in canines over millennia.

The cancer's DNA unveiled the origins of the disease in an ancient dog that was husky-like. That dog would have been medium-sized, with a grey-brown or black-colored straight coat, the BBC reported.

"We do not know why this particular individual gave rise to a transmissible cancer," lead researcher Elizabeth Murchison told the BBC.

"But it is fascinating to look back in time and reconstruct the identity of this ancient dog, whose genome is still alive today in the cells of the cancer that it spawned."

Fish oil may help preserve your brain cells
Journal: Neurology

There's been a lot of back and forth about whether fish oil, and more generally omega-3 fatty acids, are useful tools in fighting dementia. The evidence on this subject has been mixed.

A new study argues in favor of the effectiveness of fatty acids derived from fish.

Researchers looked at omega-3 fatty acid levels in 1,111 women who were participating in the Women's Health Initiative, a larger study. They found a correlation between high levels of omega-3 fatty acids and larger overall brain volume, as well as volume of a structure called the hippocampus, which is important for memory.

It's important to note that brain volume shrinkage is a normal part of aging, Jay Pottala of the University of South Dakota in Sioux Falls and Health Diagnostic Laboratory in Richmond, Virginia, told USA Today.

"This doesn't mean their brains got bigger; it just means their brains didn't atrophy as much," he said.

But MedPage today points out that this study does not actually look at brain atrophy over time, as participants only had their brains scanned once - a serious limitation to the study. There could be other reasons for the correlation - fish oil isn't necessarily causing an effect. 

Alzheimer's drugs fail in clinical trials
Journal: New England Journal of Medicine

Alzheimer's disease researchers got some bad news this week, too: Two drugs that were intended to treat the condition failed in clinical trials.

The therapies are monoclonal antibodies, and they are called solanezumab and bapineuzumab. Neither of them were effective in slowing the loss of cognitive function in patients with mild to moderate Alzheimer's disease.