CHECKUP : NEWS, TIPS AND TRENDS MUTATION LINKED TO SKATER'S DEATH.

When two-time Olympic figure-skating champion Sergei Grinkov suffered a fatal heart attack while training last November, doctors grappled with how a 28-year-old could have died so suddenly.

But an analysis of Grinkov's blood has found that he carried a genetic mutation associated with an increased risk of heart attack at an early age, according to researchers from Johns Hopkins University in Baltimore. Grinkov's father died suddenly at the age of 52.

The mutation is located at a site called P1A2, according to lead author Dr. Pascal J. Goldschmidt-Clermont, whose findings appear in the June 29 issue of the medical journal the Lancet.

Although exactly how this mutation can trigger a heart attack is unknown, researchers suspect that the gene affects the way blood platelets, which cause blood to clot, behave.

When platelets do not function correctly, tiny blood clots can form inside heart arteries and cause them to narrow - a process that can lead to heart attack, according to the researchers.

Youth movement: Teen-agers who engage in regular exercise appear to be happier than those who spend much of their time watching ``Beavis and Butt-head,'' a new report shows.

In the study of 5,000 teen boys and girls, those reporting regular exercise and participation in sports had significantly higher scores on tests of emotional well-being than their couch-potato peers.

Teens who exercised the least were more likely than their active counterparts to report feelings of upset or other signs of poor well-being, according to the study, published in the June 29 issue of the Lancet.

Because many American and British teens do not meet recommended physical activity levels, parents and teachers should encourage adolescents to participate in sports, enroll in a dance class or take up some other form of exercise, British researchers reported.

While previous studies have looked at how exercise affects adults, the new study is one of the first to examine how participating in sports affects teens, according to the researchers, led by Andrew Steptoe, a professor of psychology at St. George's Hospital Medical School in London.

Dial, then smile: Consumers will have something to smile about as the Academy of General Dentistry hosts its fifth annual toll-free dental hot line today and Tuesday, during the organization's 44th annual meeting in Portland, Ore.

``The SmileLine provides patients an excellent opportunity to ask dental questions they may be uncomfortable asking their own dentist face-to-face,'' said Dr. Paul Bussman, coordinator of this year's SmileLine. ``It gives consumers a chance to inquire about certain procedures or treatment plans they don't understand.''

Last year, more than 40,000 callers from the United States and Canada called the SmileLine. Callers were most interested in information about tooth bleaching, according to the AGD.

You can ``dial a dentist'' by calling [phone] from 5 a.m. to 5 p.m. both days.