Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:
Nearly 1 Billion Teens, Young Adults at Risk for Hearing Loss: WHO
At least 1 billion teens and young adults are at risk for hearing loss from too much exposure to loud music, both on their smartphones and at concerts and sporting events, according to the World Health Organization.
So, the agency has recommended that listening to unsafe levels of music on personal audio listening devices be limited to one hour a day.
WHO also recommended that teens take listening breaks and lower the volume on their smartphones.
In its report, released Friday, WHO said volumes above 85 decibels for eight hours or 100 decibels for 15 minutes are unsafe.
In middle- and high-income countries, almost half of all those aged 12 to 35 listen to unsafe levels of music on their personal audio listening devices or smartphones, the WHO review found.
And almost 40 percent are also exposed to loud music at nightclubs, bars and sporting events, WHO added.
"As they go about their daily lives doing what they enjoy, more and more young people are placing themselves at risk of hearing loss," Dr. Etienne Krug, WHO Director for the Department for Management of Noncommunicable Diseases, Disability, Violence and Injury Prevention, said in a WHO news release. "They should be aware that once you lose your hearing, it won't come back. Taking simple preventive actions will allow people to continue to enjoy themselves without putting their hearing at risk."
Actor Leonard Nimoy Dies of COPD at Age 83
Leonard Nimoy, best known for his role as Mr. Spock on "Star Trek," died Friday morning at age 83.
The actor was hospitalized earlier this week and died at his home in Los Angeles. His wife, Susan Bay Nimoy, confirmed his death and said the cause was end-stage chronic obstructive pulmonary disease (COPD), The New York Times reported.
Last year, Nimoy announced he had the disease and said it was caused by his years of smoking, which he gave up three decades ago.
Nimoy was cast as Mr. Spock -- the Vulcan first officer of the starship Enterprise -- in the original "Star Trek" series, which first aired in the mid-1960s but was canceled after three seasons. Nimoy continued to play Spock in subsequent movies and TV series, with his last appearance in the 2013 movie "Star Trek Into Darkness."
U.S. Military Ends Ebola Mission in Liberia
The United States' military officially ended its five-month Ebola aid mission in Liberia on Thursday.
At one point, there were 2,800 U.S. military personnel in Liberia, but the number gradually fell as the epidemic began to subside. The Pentagon said nearly all troops will be gone from Liberia by the end of April, Agence France-Presse reported.
"The importance of the progress we see today means more than just the reduction in the number of new or suspected cases of Ebola," mission commander Major General Gary Volesky said. "This progress is also about Liberians being able to get back to a normal way of life."
About 100 U.S. troops will remain in the region to boost the "disease preparedness and surveillance capacity" of local governments, the Pentagon said.
Liberia was hardest hit by the Ebola outbreak in West Africa, accounting for 4,037 of the approximately 9,600 deaths. The outbreak began in Guinea in December 2013 and at its height, Liberia and Sierra Leone had between 300 and 550 confirmed, suspected and probable Ebola cases a week, AFP reported.
As of last Sunday, there have been fewer than 400 new cases in all three countries in the previous three weeks, according to the World Health Organization.
U.S. Abstinence Programs in Africa Ineffective Against HIV/AIDS: Study
U.S. efforts to promote abstinence and fidelity in Africa in order to prevent the spread of HIV have been largely useless, a new study says.
The $1.3 billion spent on the program since 2005 did not measurably change sexual behavior, second-year Stanford Medical School student Nathan Lo said at an AIDS conference in Seattle, The New York Times reported.
Lo's work was overseen by Dr. Eran Bendavid, an assistant professor of medicine at Stanford, who has conducted previous analyses of American global anti-AIDS programs for the Institute of Medicine, part of the National Academy of Sciences.
The findings were applauded by critics of the U.S. policy of promoting abstinence and fidelity as a way to combat HIV/AIDS.
"That was fantastic," said Dr. Gilles van Cutsem, medical coordinator for Doctors Without Borders in South Africa, The Times reported.
Restrict Use of New Meningitis Vaccines: Experts
Two newly-approved meningitis vaccines should be used sparingly, a U.S. expert panel says.
The vaccines should be restricted to vulnerable people during outbreaks and not given routinely to teens and college students, the Advisory Committee on Immunization Practices said Thursday, NBC News reported.
The two vaccines -- Trumenba and Bexsero -- were approved by the Food and Drug Administration to protect against the B strain of meningits. However, insurers usually don't pay for vaccines unless they're recommended by the advisory committee.
The decision is likely to anger parents who lobbied for wider use of the two vaccines, NBC News reported.