Grandma doesn't spend much time online — but she would be better off if she did, researchers agree.

Some 92 percent of Americans ages 18-29 are online (meaning they admit to using the Internet and e-mail at least occasionally), according to the Pew Internet and American Life Project. The rate falls modestly to 87 percent for those ages 30-49, and somewhat more steeply to 79 percent to those ages 50-64. But for those 65 and older the rate falls of a cliff, to 42 percent.

But a recent study by the Phoenix Center for Advanced Legal & Economic Public Policy Studies, a non-profit think-tank in Washington, DC, indicates that spending time online cuts the incidence of depression among senior citizens by at least 20 percent. The results were based on surveys of 7,000 people age 55 and older who were retired and not working, but not living in nursing homes.

"Increased Internet access and use by senior citizens enables them to connect with sources of social support when face-to-face interaction becomes more difficult," said study co-author Sherry G. Ford, a professor at the University of Montevallo in Montevallo, Alabama. Hence, they are less susceptible to depression.

"Considering that depression costs the U.S. economy about $100 billion annually, Internet use for the elderly may have a significant payoff," concluded the 26-page study.

Since 62 percent of the $100 billion cost is shouldered by employers, and assuming that senior citizens are 30 percent of the population, cutting the depression rate by 20 percent would save the nation more than $2 billion in direct costs, the study estimated.

Another recent study found that first-time use of the Internet by older adults enhanced brain function and cognition.

There is more to seniors' resistance to surfing the web than sheer crotchetiness, other research shows.

Aging often involves decreased memory, attention, cognitive speed, visual acuity, and fine motor control — the same capacities needed to use a computer. So it's no surprise that senior citizens typically take twice as long to learn digital skills, and are more prone to errors when they do get online, says Neil Charness of Florida State University.

Consequently, they may decide that the results are just not worth the effort.

To close the digital divide, Charness and colleagues called for more attention to the digital needs of the elderly. Their suggestions include:

* Web sites with higher contrast, larger fonts, minimal scrolling, more navigational aids, and more user help.

* Cell phones with simpler menus, larger fonts, larger buttons, and noise filters.

They also suggest more computer-based brain fitness games for the elderly, since they can slow or even reverse age-related declines in perception and cognition, research shows. However, there is as yet little evidence these games can boost the user's overall quality of life.