Here are some of the latest health and medical news developments, compiled by editors of HealthDay:

AMA Mum on Menthol Cigarette Exemption

The American Medical Associated voted Tuesday to defer comment on a proviso in federal tobacco legislation that would grant an exemption to menthol while banning other cigarette flavor additives such as mint, clove, and vanilla.

The AMA voted "to refer the decision on menthol to its board, effectively silencing the doctors who wanted the organization to speak out against the exemption," the Associated Press reported. The exemption is key to a compromise that would give regulatory control of cigarettes to the U.S. Food and Drug Administration.

While the other additives tend to be favored by younger people, menthol is preferred by more than 75 percent of blacks who smoke. That compares to fewer than 25 percent of whites who smoke, the AP said, citing government estimates.

Former Secretary of Health and Human Services Louis Sullivan, who held the post from 1989 to 1993, is among seven former health secretaries who have written to Congress opposing the menthol exemption.

"If we're banning things such as clove and peppermint, then we should ban menthol," he said. "This bill [if it includes the exemption] will be discriminatory against African-Americans."

But AMA President Dr. Ron Davis is among those who favors keeping the exemption, having said that removing it could threaten passage of the entire bill, the AP reported. "It would change the entire political dynamic," he said.

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New Alzheimer's Drug Shows Promise

The experimental Alzheimer's disease drug bapineuzumab appears to be effective in some patients, according to mid-stage study results released Tuesday by drug makers Wyeth and Elan Corp, the Wall Street Journal reported.

In patients with a gene known to increase the risks of Alzheimer's -- and of developing the disease at an earlier stage -- the drug showed statistically significant clinical improvements. This did not occur in patients without the gene, who were at greater risk for fluid buildup in the brain, especially when taking the drug at higher doses.

Detailed results of the study are expected to be presented July 29 at the International Conference on Alzheimer's Disease in Chicago. The drug has received a fast-track designation from the U.S. Food and Drug Administration. It's expected that it will be at least two years before Wyeth and Elan apply for FDA approval of bapineuzumab, the Wall Street Journal reported.

The drug is designed to attack beta-amyloid. Many experts believe that a build-up of this substance in the brain causes Alzheimer's disease.

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U.S. Employers Facing Big Increases in Health Care Costs

Health care costs for American employers are expected to increase 9.9 percent this year and another 9.6 percent in 2009, says a PriceWaterhouseCoopers study released Tuesday.

There are two main reasons for the rising costs, the study said. One is an increase in the expenses people with insurance are paying for people without coverage. Second, many hospitals are replacing facilities and adding private rooms and outpatient treatment centers, the Associated Press reported.

"Health care providers, insurers and employers will have to monitor medical costs carefully if we are to avoid a resurgence of the double-digit annual increases seen in the past," said Dr. David Chin, leader of the Health Research Institute at PriceWaterhouseCoopers.

In an effort to control health care costs, study leaders said employers are increasing wellness, prevention and disease management programs designed to keep workers healthy and boost productivity, the AP reported.

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New Egg Freezing Method Called Safe

A new method of freezing human eggs for later use is as safe as conventional in vitro fertilization (IVF) treatment, say Canadian researchers, who looked at 200 children conceived using eggs that were rapidly frozen using a process called vitrification.

In this method, water is removed from the egg, an "antifreeze" solution is added, and the eggs are then flash frozen in liquid nitrogen, BBC News reported. Up to 95 percent of eggs survive vitrification, compared with 50 percent to 60 percent of eggs frozen using older methods.

The Canadian team found that about 2.5 percent of the children born using vitrified eggs had birth defects, which is about the same as in natural pregnancies and conventional IVF.

The study appears in the journal Reproductive Biomedicine Online.

Additional studies are needed before the safety of vitrification can be established, Dr. Allan Pacey, the secretary of the British Fertility Society, told BBC News.

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AMA Report Card Rates Insurers

A report card that compares how quickly and accurately health insurers pay doctors was released Monday by the American Medical Association. The report card, based on an analysis of three million claims, compares Medicare and seven national commercial insurers, the Associated Press reported.

About 98 percent of medical services billed were paid by Medicare at the contracted rate, compared with 71 percent for Aetna and 62 percent for United Healthcare, which had the lowest rate of contract compliance.

Doctors and their billing services share responsibility for prompt payment, United Healthcare spokesman Gregory Thompson told AP.

"Data show there is often a significant lag time between when services are provided and physician claims are submitted," he said.

The aim of the report card is to lower claims processing costs and help doctors negotiate contracts with insurance companies, the AP reported. A reduction in wasteful administration costs (estimated at $210 billion a year) will help patients, said Dr. William Dolan, an AMA board member.

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Bone Density Screens Can Be Done Every Five Years: Study

Screening for bone loss in older adults can be done as infrequently as every five years, according to Canadian researchers who looked at 9,423 people, ages 25 to 85.

They found that women ages 50 to 54 had the most pronounced bone loss of all the participants -- 1.3 percent. The researchers said this decrease is within the margin of error of most bone density screening machines, which means that amount of bone loss is not as significant as previously believed, CBC News reported.

"The extent of bone loss that we observed suggests that repeat measurements of bone density could be delayed to intervals of up to five years in the absence of other risk factors," the researchers wrote.

Their findings was published Tuesday in the Canadian Medical Association Journal.

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Marijuana May Harm Fetal Brain

Smoking marijuana while pregnant may harm the developing brain of a fetus, say researchers at the University of Aberdeen in Scotland.

In tests on mice, the researchers found that marijuana can affect molecules essential to a signaling process that plays a role in normal brain development. The researchers also found that certain prescription drugs, including some used to treat obesity, can have a similar effect, BBC News reported.

"Our findings highlight that the integrity of this signaling system should be maintained and not disrupted if the brain is to develop normally," said Professor Tibor Harkany. "Anything that disrupts this process ... could ultimately affect the brain's functionality."

The study was published in the journal Proceedings of the National Academy of Sciences.

Previous research has suggested that children born to women who used marijuana while pregnant experienced problems with physical activity, BBC News reported.