When we were young and cruel, our reflexes lightning fast, our vision 20/20, a friend of mine imitated an old person driving. He slid down on the leather seat, death-gripped the wheel, hunched toward the windshield, and slowed to eight miles an hour. Gasping in mock protest, I had to laugh. He had captured a transformation we were sure we, who saw it so clearly, would never undergo ourselves.
Ah, but we will. I already get a few more outraged honks than I used to. Old drivers slow down, because their bodies and their reaction time have slowed down. These days, my hope is that senescent Baby Boomers will calm the roads, restore the need for patience and understanding before it is my turn for white knuckles.
Because what we need to be vigilant for is the opposite of slowing down.
Jason Doherty, a Washington University research statistician I met at, of all places, our neighborhood dog park, used the time our dogs spent romping to tell me about his team’s latest finding. The DRIVES Project, led by Dr. Ganesh Babulal, has been busy. When Jason finished his account, I sat down hard on the bench.
Reckless driving can indicate preclinical Alzheimer’s disease.
Preclinical refers to a reassuringly long period, fifteen to twenty years, when the disease starts in the brain but is not yet having any obvious effect on memory, thinking, or behavior.
DRIVES is one of the first studies to measure specific driving behavior over time. And what the team has already learned is that well before any cognitive signs of dementia show up, reckless driving—hard stops, sudden acceleration, speeding—indicates its future onset.
“Why driving?” I ask, thinking of all the other lapses that trouble anybody over a certain age. (The age at which we are certain of our opinions. Certain who we are. Certain we will die in less time than we have already been alive.) We panic and make nervous jokes about senior moments: looking for the glasses atop our head. Hunting runaway car keys. Groping for the names, dissolved into the mist, of people we know and even like. Forgetting why we went down to the basement in the first place.
Meanwhile, we watch friends drive like Chicago cabbies, zooming then slamming on the brakes, blithely straddling two lanes, sailing along at seventy in a forty, and we grudgingly admire their panache. They are not worried about their fuzzy bifocals or their short-term memory.
But they may have more to worry about in the future.
Neuroscientists have already identified the main biomarker associated with Alzheimer’s disease: abnormalities in levels of the amyloid beta protein. Those levels show up in cerebrospinal fluid, which was tested regularly for the study participants. So was the volume of their hippocampus. So were their cognitive skills.
An estimated 30 to 40 percent of cognitively normal adults are classified as having preclinical Alzheimer’s, based on sensitive tests of biomarkers for brain pathology. They are still functioning normally, but they are more likely to fail a road test, and they are at increased risk of traffic violations and crashes. The riskiest factors are those chosen by the researchers: speeding, hard braking, and sudden acceleration. Not creeping along scared to merge. That can be risky, too, and it exasperates the young ’uns. But mainly, it shows an awareness of slowed reflexes and dulled vision and an attempt to compensate by avoiding risk, driving more carefully, driving less often.
Those with preclinical Alzheimer’s often lack such caution, and their risky driving worsened over time, while their peers’ risks lessened because they deliberately took fewer chances. Older adults with preclinical Alzheimer’s may begin to score lower on cognitive tests as time goes by, but those cognitive changes are nowhere near dramatic enough to account for the increase in risky driving.
So what does?
Another study by The DRIVES Project looked at memory, processing speed, and attention (the ability to focus and ignore distractions). Drivers who were losing some of their sharp focus and ability to concentrate drove less each month, drove less at night, went to fewer new places, and made shorter trips. But in those with preclinical Alzheimer’s, attentional control explained only about 1 percent of their worsening driving score. No cognitive changes predicted the increases in hard braking, sudden acceleration, or speeding.
“Driving behavior is a dynamic activity requiring rapid, sustained, and coordinated deployment of several conscious and subconscious systems (cognitive, motor, sensory, affective),” the team notes in its conclusions. “The constraints and demands widely vary.”
Because driving takes so much fluid awareness and complex response to whatever the hell the driver in front or alongside you just did, it turns out to be a great early warning system for invisible changes deep inside the brain. Maybe those with preclinical Alzheimer’s disease are less able to detect the limitations brought on by aging. Maybe they are less able to moderate their own impulsive driving behavior.
But here is the oddest (to my untrained mind) finding of all: those who showed biomarkers of preclinical Alzheimer’s and had already begun to lose volume in their hippocampus (the seat of memory, emotion, and unconscious stress response) had less of an increase in risky driving. In those who had not yet begun to lose hippocampal volume, the risky behavior worsened. One possible reason, Doherty says, is that until the hippocampus begins to shrink, people are less likely to experience memory issues, so they are overconfident in their driving.
The good news here is the possibility of early detection. Really early, before any cognitive changes begin. Being injured or dying in a car crash—or hurting or killing someone else—is up to five times more likely if you have Alzheimer’s disease. But caution can be exercised early on, now that we know that reckless driving—which can look as nonchalant as a teenager zig-zagging down the highway with one finger on the wheel—is more ominous than brave. The opposite of the old-driver stereotype, this is the pattern we should have worried about all along.
Read more by Jeannette Cooperman here.
