Utah health officials say there's not much mystery as to why the latest mortality statistics show men are catching up with women when it comes to longevity.

It's all a matter of the heart.A new life-expectancy study conducted by Metropolitan Life Insurance Company found that between 1989 and 1996, men gained a year of expected life; women gained 2.4 months.

That gain is likely due to the decline in heart-disease deaths among men, said Robert Rolfs, an epidemiologist with the Utah Department of Health.

"Heart-disease death rates are higher for men than for women. You would expect improvements might shrink that gap a little," he said.

MetLife used figures from the National Center for Health Statistics to determine that boys born in 1996 can expect to live 72.8 years on average, while baby girls can look forward to 79 years.

Those life expectancies translate to a 4-year increase for men since 1975 and 2.4 years for women. Men's life span at birth is now at an all-time high. The women's record was set in 1992, when their average life expectancy was estimated to be 79.1 years.

Michael Friedrichs, a statistician with the Department of Health's chronic-diseases program, found that males in Utah do a little better than their national counterparts.

His calculations show that Utah boys born in 1996 have a life expectancy of 74.9 years. Utah girls are in line with the rest of the country at 79 years.

The gap at birth is always wider than it is later in life, partly because men are more likely to die young than women. By the time those boys and girls born in 1996 are 75, their life span gaps are expected to have narrowed considerably: 83.8 years for men, and 84.9 years for women. That is slightly better than the estimates for the nation, which show men born in 1996 will die 2.1 years sooner than women.

"You can see from that pattern, if you are a male and make it to 75, your life expectancy isn't that much different from a woman's," Friedrichs said.

Nationwide, the increase in men's life spans is due to improved medical treatments such as better emergency response and heart surgeries. Other major factors include better diets, more exercise and less smoking.

"Tobacco use at one time was much higher for men than for women. But women's use increased," Rolfs said. "It might be that men have benefited more from the decline in smoking."

The fact that Utah residents smoke less than the rest of the country contributes to their higher life expectancy. But the state's residents have other behaviors that are deadly.

"Diet and activity patterns are what kill people in Utah," Friedrichs said. "In 1900, tuberculosis was a leading cause of death. In 1998, people die of chronic diseases. So what we die of has changed. Our behavior is what kills us. Your channel changer and your automatic garage opener, they have created a society that is sedentary."

Health studies show that 27.2 percent of Utahns in 1996 got moderate exercise; 21.4 percent claim to eat 5 servings of fruits and vegetables per day; and 25.2 percent are obese. That sounds terrible, but compared to other states, Utah is doing well, Friedrichs said.

"Wisconsin is the fattest state," he said. "The New England and Rocky Mountain states are generally more active."