Assessing Fitness to Drive

In this section

1.2.1. General considerations

1.2.2. Vasovagal syncope

1.2.3. Blackouts due to medical causes not covered in the standards

1.2.4. Blackouts of undetermined mechanism

Blackouts may occur due to a range of mechanisms including:

• vasovagal syncope or ‘faint’, which accounts for more than 50 per cent of blackouts and may be due to factors such as hot weather, emotion or venepuncture but may also be due to more serious causes that may recur
• syncope due to other cardiovascular causes such as structural heart disease, arrhythmias or vascular disease
• epileptic seizure, which accounts for less than 10 per cent of blackouts
• other causes including metabolic causes (e.g. hypoglycaemia), drug intoxication or a sleep disorder.

Determination of the mechanism of a blackout may be straightforward based on history, investigations and specialist referral, and the person may be managed as per the appropriate chapter. Alternatively, it may require extensive cardiovascular and neurological investigations and referral to several specialists. People should be advised not to drive until the mechanism is ascertained and the corresponding standard met.

Some drivers may attribute a crash or driving mishap to a ‘blackout’ to excuse an event that occurred for some other reason such as inattention or distraction (e.g. a mobile phone conversation). There will also be a small proportion of cases in which a clear cause cannot be established.

See references 1, 2, 3, 4

The most common cause of transient loss of consciousness is vasovagal syncope (‘fainting’). Where this has been triggered by a well-defined provoking factor or a situation that is unlikely to recur while driving (e.g. prolonged standing, venepuncture or emotional situation), it is not necessary to restrict driving. However, vasovagal syncope may also result from other causes that are not so benign. In such cases, fitness to drive should be assessed according to the cardiovascular conditions standards for syncope (refer to section 2. Cardiovascular conditions).

See reference 5

If the cause of the blackout is determined to be a medical condition not covered in the standards, then first principles regarding fitness to drive should be applied (refer to Part A section 2. Assessing fitness to drive – general guidance). Considerations include the likelihood of recurrence of blackout and the treatability of the condition as well as the nature of the driving task. There should also be an appropriate review period. A more stringent approach should be considered for commercial vehicle drivers.

If, despite extensive investigation, the mechanism of a blackout cannot be determined, fitness to drive should be assessed according to section 1.3. Medical standards for licensing. The standards for blackout of undetermined mechanism are similar to those for seizure.