Medical assessment involves a review of medical conditions and drugs that could impair driving ability. In general, any condition or drug that can impair consciousness should raise concern about driving safety.

Falls

Falls and motor vehicle crashes share common causative factors (eg, impaired vision, muscle strength, cognition). A history of falls in the past 1 to 2 yr indicates increased risk of crashes and should prompt further evaluation of physical functioning (see above).

Cardiac disorders

Cardiac disorders may increase driving risk. General guidelines include refraining from driving for

• 1 mo after MI, coronary artery bypass surgery, or stabilization of unstable angina symptoms
• 3 mo after arrhythmia with syncope
• 6 mo after internal cardioverter defibrillator placement or after resuscitation required because of sustained ventricular tachycardia or ventricular fibrillation

Patients with severe heart failure (eg, class IV heart failure, dyspnea at rest or while driving) should refrain from driving until they can be evaluated with on-road testing.

Neurologic disorders

Neurologic disorders also increase driving risk. Specific disorders include

• Stroke or transient ischemic attack (TIA): Drivers with a single TIA should wait 1 mo before resuming driving; those with recurrent TIAs or stroke should be event-free for at least 3 mo before resuming driving. Physical examination should be done to assess how residual disability due to stroke may affect driving ability.
• Seizures: Regulations for drivers who have seizures are state-specific, but most states require a seizure-free interval (often 6 mo) before they reinstate driving privileges. Anticonvulsants can adequately control seizures in about 70% of patients, although relapses may occur when these drugs are withdrawn.

Many other neurologic disorders (eg, Parkinson's disease) cause disability and should be monitored by functional assessment and possibly an on-road test.

Diabetes mellitus

Diabetes mellitus poses a risk because patients may become hypoglycemic while driving. Patients who have had a recent hypoglycemic episode affecting awareness should not drive for 3 mo or until factors contributing to the episode (eg, diet, activity, timing and dose of insulin or antihyperglycemic drug) have been assessed and managed. Sensory changes in the extremities due to diabetes can also impair driving ability.

Sleep disorders

Sleep disorders, most notably obstructive sleep apnea syndrome, can cause drowsiness leading to crashes, and patients should refrain from driving until they are adequately treated.

Drugs

When starting a new drug that could affect visual, physical, or cognitive function, patients should refrain from driving for 1 to 2 days to be sure no adverse effects occur. Drugs that increase driving risk include

• Antihistamines, benzodiazepines, opioids, anticholinergics, hypnotics, antihypertensives, or tricyclic antidepressants: These drugs increase driving risk because they can cause drowsiness; some can also cause hypotension or arrhythmias.
• Antiparkinsonian dopamine agonists (eg, pergolide, pramipexole, ropinirole): These drugs occasionally cause acute sleep attacks, which pose an especially high risk of crashes.
• Antiemetics (eg, prochlorperazine) and muscle relaxants (eg, cyclobenzaprine): These drugs are cause for concern because of their potential for altering sensory perception.

Instructing patients to bring all drug containers to the office can help identify drugs that increase risk.

Older adults are involved in fewer alcohol-related fatal crashes. Fewer older adults consume alcohol, but limiting alcohol consumption is still important because blood alcohol level per amount of alcohol consumed is higher in older adults. Also, concurrent use of alcohol and other drugs, particularly multiple drugs, further impairs cognition, increasing the risk of crashes.

Last full review/revision October 2009 by David B. Carr, MD; Peggy P. Barco, MS, BSW, OT/L