On Tuesday you can’t find the car keys. On Saturday you rush into the kitchen and forget (for three seconds) why you’re there. Who among us, positive or negative, doesn’t sometimes fear we’re losing our minds? These days, that fear seems a national obsession—witness the boom in Alzheimer’s research and other studies suggesting that playing Mozart and Sudoku can keep our brains buff.

For people with HIV—who now routinely reach their golden years—the dread can be numbing. Alzheimer’s rates aren’t higher among those with HIV, but many do fear AIDS dementia, remembering the days before combo therapy when the virus often destroyed body and mind. Says 20-year HIV survivor Wallace Corbett, 46, of Washington, DC, “My partner, a concert pianist, had dementia in his final year of life. He forgot how to play.” Though Corbett’s health is good, he fears the same fate. “Sometimes at work I forget something and I think, ‘Is this it?’ The lapses are usually just stress-related,” he says, “but with HIV, you get paranoid.”

Thanks to HIV meds, some researchers estimate that dementia now affects fewer than 2% of positive people; it’s still seen in late stages of AIDS when CD4 counts hit bottom, especially with opportunistic infections or a history of drug use or alcoholism. For people on combos, with CD4s above 200, the real challenge is “brain fog”—a much subtler and slower diminishing of brain function. The term is, well, foggy, covering everything from sporadic forgetfulness to persistent minor cognitive motor disorder (MCMD), where memory lapses become habitual, with personality changes and decreased motor skills.

Mary Catherine George, research manager at Mt. Sinai Medical Center in Manhattan, says doctors there see MCMD in a few “high functioning” HIV long timers like nurses or executives—most with low CD4 counts, though still above 200—who become unable to perform their complex jobs. Mt. Sinai’s Elizabeth Ryan, PhD, says that while “we’re not sure whether MCMD sometimes develops into dementia,” it can go away. For stubborn cases, current remedies include behavioral therapies and drugs for particular symptoms, such as antipsychotic meds for abrasive behavior.

Brain fog can stem from hep C, street drugs or HIV-related illnesses; researchers are focusing on HIV’s relationship to the brain. When you contract the virus, it enters the brain and doesn’t leave. “HIV drugs control the virus in the body,” says researcher Harris Gelbard, MD, of University of Rochester Medical Center in New York, “but no combo has been shown to eliminate HIV from the brain,” and chronic inflammation may result. Over decades, Dr. Gelbard believes, this may cause some loss of brain function.

What adds to the confusion, says Giovanni Schifitto, MD, who works with Dr. Gelbard, is that depression is often misdiagnosed as dementia or MCMD because “the symptoms [including concentration problems, social withdrawal, agitation and anxiety] are similar.”

Some researchers advocate HIV meds that penetrate the brain—Viramune (nevirapine), Sustiva (efavirenz), Ziagen (abacavir) and others—especially once MCMD appears. But none of these eliminates HIV from the brain, and studies haven’t confirmed the strategy. Cincinnati’s Judith Feinberg, MD, and Barbara Zeller, MD, of New York City’s Project Samaritan emphasize that controlling HIV overall, regardless of which meds you take, remains the best approach.

So Dr. Gelbard says, use those brain-teasers, and discuss any symptoms with your doc. “Don’t worry,” he adds. “We’re working hard so the remedies will be ready when more people get to the point of needing them.” Got that?