Should Dementia Patients Taking Antipsychotics Refrain From Driving?

TUCSON—Nearly one in five drivers with Alz­heimer’s disease who are taking a cholin­es­terase inhibitor has been involved in a motor vehicle collision, with fewer than 40% deemed to be driving properly at the time of the accident, according to Mark Rap­oport, MD, and colleagues. Collisions were significantly more likely to occur when a patient with dementia was undergoing anti­psychotic treatment than when he or she was not. The findings were presented at the 18th Annual Meeting of the American Neuropsychiatric Association.

Prior research has found that crash rates among patients with dementia are two to eight times higher than for age-matched controls. Other research has shown that many patients with dementia continue to drive and that about one third of these patients have had at least one accident before discontinuing driving. However, noted Dr. Rapoport, the relationship between antipsychotic use and driving had not been previously examined.

Dr. Rapoport’s group conducted their study in a cohort of patients with mild to moderate dementia. All participants were treated with a cholinesterase inhibitor and were involved in a motor vehicle collision. The investigators sought to determine whether the patients who had a collision were more likely to have had an antipsychotic dispensed to them in the four months preceding the collision than were those who were not hospitalized for a collision. They also wanted to find out whether older drivers who were taking cholinester­ase inhibitors and had motor vehicle collisions were more likely to have been exposed to antipsychotics in the four months preceding the collision than during the same four-month period from the previous year.

Driving With Dementia

The researchers obtained information concerning prescription drug use, motor vehicle accidents, and hospitalizations from various databases for residents 65 and older in Ontario. For the nested case-control analysis, participants were older drivers with active licenses who had received a prescription for a cholinesterase inhibitor. Cases were drivers involved in collisions, while controls were drivers who had not been in a collision and were matched by age, gender, and rural or urban status.

Dr. Rapoport and colleagues adjusted for a number of confounders, including any prescription for lithium, antidepressants, benzodiazepines, mood stabilizers, or anticonvulsants within 120 days prior to index date and psychiatric hospital admissions 10 years prior to index date. They also adjusted for other prescribed drug therapies, visits for a diagnosis of visual impairment in the five years prior to entry date, number of nonpsychiatric hospitalizations in the five years prior to index date, and number of motor vehicle collisions and violations while the patient was the driver in the five years prior to entry date.

For a separate, population-based, case-crossover analysis, the cohort consisted of older drivers with active licenses who had received a prescription for a cholin­esterase inhibitor and were involved in a motor vehicle collision, with each driver serving as his or her own control. The researchers contrasted antipsychotic use among participants in the four months prior to the collision. Benzodiazepines were used as a positive control, and antifungals were used as a neutral control.

A total of 53,562 patients received a prescription for a cholinesterase inhibitor during the study period, and from that group, 14,558 patients (27%) had a valid driver’s license. The researchers found that 2,703 patients (19%) with a valid driv­er’s license who took a cholinesterase inhibitor were involved in a motor vehicle accident. “Most of the collisions occurred prior to the prescription for a cholinesterase inhibitor (84%), while 16% occurred after the cho­linesterase inhibitor prescription,” said Dr. Rapoport, staff psychiatrist at the Sunnybrook Health Sciences Centre in Toronto.

A breakdown of the collisions revealed that 1,958 accidents involved property damage, 575 involved nonfatal injury, and three resulted in fatalities. A total of 856  patients (33.7%) were driving properly at the time of their collision. Among the reasons cited for the accidents, 457 drivers (18%) failed to yield the right of way, 209 (8%) made an improper turn, 166 (6.5%) lost control, 156 (6%) were following another vehicle too closely, and 122 (5%) disobeyed a traffic signal; 426 accidents (16%) were labeled as “other,” and in 151 cases (6%), the reason for the accident was unknown.

Within the nested case-control analysis, Dr. Rapoport’s group found that a higher percentage of controls (1.5%) had accidents compared with cases (0.9%), a finding that was “counterintuitive,” said Dr. Rapoport. “The most parsimonious explanation is reduced driving exposure,” he said. “Self-restriction is incomplete. Many patients with both Alzheimer’s disease and recent antipsychotic treatment are on the roads.”

As for the case-crossover analysis, the researchers found that of the 2,708 cases involving a collision during this time period, 11 drivers had been censored prior to their collision. Of those involved in collisions, 2% had been exposed to antipsychotics. Thirty-five patients (1.3%) were exposed to an antipsychotic in the four months prior to a motor vehicle collision. Fewer than five patients (0.1%) had been exposed to an antipsychotic within the same four months of the prior year.

“The case-crossover design has the advantage of controlling for individual differences between the subjects, potentially including differences in driving exposure,” said Dr. Rapoport. “Motor vehicle accidents were significantly more likely during an era of antipsychotic treatment than when patients were untreated. However, the small sample size led to wide confidence intervals. The results regarding anti­psychotics must be considered preliminary, as the case-control and case-crossover designs yielded opposite findings. We are currently expanding the cohort of dementia to increase the validity and robustness of our results.”        

—Colby Stong

Suggested Reading
Cummings JL, Frank JC, Cherry D, et al. Guidelines for managing Alzheimer’s disease: part II. treatment. Am Fam Physician. 2002;65:2525-2534.

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