The U.S. government on Monday released new dietary guidelines urging all Americans to cut their daily salt intake by one-third and those over 50 to make more drastic reductions.

'"The 2010 Dietary Guidelines are being released at a time when the majority of adults and one in three children is overweight or obese," Agriculture Secretary Tom Vilsack said in a statement.

Children injected with the Pandemrix swine flu vaccine were nine times more likely to contract narcolepsy than those who were not vaccinated, a preliminary study by Finland's National Institute for Health and Welfare, THL, showed Tuesday.

"Currently, the most likely explanation is that the increase in narcolepsy is by joint effect of the vaccine and some other factor(s)," THL said.

A section of the brain involved in memory grew in size in older people who regularly took brisk walks for a year, researchers reported Monday.

The new study reinforces previous findings that aerobic exercise seems to reduce brain atrophy in early-stage Alzheimer's patients, and that walking leads to slight improvement on mental tests among older people with memory problems.

U.S. researchers have found a way to predict how successful a smoker will be at quitting by using an MRI scan to look for activity in a region of the brain associated with behavior change.

The scans were performed on 28 heavy smokers who had joined an anti-smoking program, according to the study published Monday in the peer-reviewed journal Health Psychology.

Moscow and at least two other cities shut all their elementary schools Saturday to help fight one of the worst flu outbreaks to hit central Russia in more than a decade, officials said.

The Moscow closure would affect more than 1,500 schools.

Venezuelan health authorities appealed Thursday to more than 400 people exposed to cholera at a wedding in the Dominican Republic to report for treatment in order to head off an epidemic.

So far, 37 people have been treated for cholera in Venezuela but authorities were still trying to locate the rest of the 452 people who traveled to the Dominican Republic for the January 22 wedding.

Eating foods high in trans-fats and saturated fats increases the risk of depression, according to a Spanish study published in the U.S. Wednesday, confirming previous studies that linked "junk food" with the disease.

Researchers also showed that some products, such as olive oil, which is high in healthy omega-9 fatty acids, can fight against the risk of mental illness.

Bill Gates' foundation and Abu Dhabi's crown prince are donating $50 million each to vaccinate children in Afghanistan and Pakistan against polio and other diseases.

Sheik Mohammed bin Zayed Al Nahyan and the Bill and Melinda Gates Foundation say two-thirds of the funds will go toward a pair of vaccines against pneumonia, diphtheria, whooping cough and other ailments afflicting young children in Afghanistan. The rest will be given to the World Health Organization and UNICEF to provide polio vaccines in Afghanistan and Pakistan.

Federal health officials said Wednesday they are investigating a possible link between breast implants and a very rare form of cancer, raising new questions about the safety of devices which have been scrutinized for decades.

The cancer, known as anaplastic large cell lymphoma, attacks lymph nodes and the skin and has been reported in the scar tissue which grows around an implant. The Food and Drug Administration is asking doctors to report all cases of the cancer so the agency can better understand the association.

Exposure to road traffic noise boosts the risk of stroke for those 65 or older, according to research published online Wednesday in the European Heart Journal.

In a survey of more than 50,000 people, every 10 additional decibels of road noise led to an increase of 14 percent in the probability of a stroke when averaged for all age groups.