W ASHINGTON — Reading this sentence is good for your mental health. In fact, reading anything is good for you.

It may also be helping generations to come.

The problem is, we’re becoming a country of non-readers. And, as our librarian first lady could say, only in a more grammatically correct way, that ain’t good.

First, a science lesson. Brain researchers have long known the link between mental exercise (think of reading as a Stairmaster workout) and a healthy life. It’s the brain’s internal wiring and something called synapses (electrical impulses; think spark plug) that control body functions … like thinking. As long as the wiring and synapses thingies are in tune, all’s well. It’s when they slip into disuse that mental abilities begin to fade. As they say, use it or lose it.

It doesn’t matter whether one spends quality time with Jane Austen or John Grisham, the Wall Street Journal or the local Daily Fish Wrapper, the act of reading helps keep the brain active and keeps those spark plugs firing away. Have nothing handy? Check out the label on a can of soup. Whatever.

For the record, other gray-matter calisthenics include playing word games and board games, dancing, learning a foreign language, doing your own math instead of using a calculator and writing. Snippy e-mail missives don’t count.

Just last summer a National Endowment for the Arts survey found a dramatic decrease in Americans who read literature (novels, plays, poetry, short stories), with more than half — HALF! — of Americans not reading for pleasure. The survey found an overall decline of 10 percentage points in literary readers from 1982 to 2002, a loss of 20 million potential readers.

Said NEA Chairman Dan Gioia: “The decline in reading among every segment of the adult population reflects a general collapse in advanced literacy. To lose this human capacity — and all the diverse benefits it fosters — impoverishes both cultural and civic life.”

While the NEA survey found reading declines in all demographic groups, it was particularly dramatic among those 18 to 24 years old. Among this group, the decline was 55 percent greater than that of the total adult population. At the current rate of loss among the young, literary reading will virtually disappear in 50 years, the NEA warns. That’s not exactly reassuring.

Not to say that America is racing toward becoming a land of clueless mush-heads, MTV notwithstanding. But it does raise concerns about our culture. Granted, ridding the land of much of today’s pop culture isn’t such a bad idea. Quite the contrary. But it’s that culture of literacy, decency, manners, interests and tastes that we inherited from our grandparents and their grandparents that we must not allow to disappear.

A scary thought: Imagine a generation or two from now no one could tell who Tom Sawyer or Huck Finn are. Or know any of the chivalrous exploits of the Knight of the Rueful Countenance. Or think Annabelle Lee is a movie starlet.

Our culture would be greatly diminished.

At the other end of the age spectrum, it is the older person who can benefit from a lively novel that engages the imagination. Reading forces us to think, to keep those little synapses rat-a-tat-tatting.

Note to Gramps: We are not suggesting that mental decline is a fact of aging. It definitely is not. In fact, some brain functions — judgment, wisdom — improve with the years.

A report in the June 2003 New England Journal of Medicine found that seniors can reduce their risk of dementia 35 percent by reading several times a week. Other activities were found to be even more beneficial in reducing the risk: playing a musical instrument, 69 percent; and learning new dance steps, 76 percent.

The concern is with the retiree who after a career of being mentally engaged at work suddenly finds himself with little to do other than watching trees grow. Talk about letting those synapses snooze. Can memory loss be far behind?

It doesn’t have to be that way. Check out what’s on the bookshelf and devour it. Your brain can use the exercise. In fact, the NEA survey found that readers are more likely to be involved in cultural, sports and volunteer activities than are non-readers.

Keep on synapsing; it just might help you win over new friends and influence people. You’re on your own in the “handsome” department, but we guarantee readers an uptick in the “witty” and “wise” categories.

A grateful nation thanks you.