There is a document on the ATSB site that addresses pilot incapacitation involved in accidents and incidents from 1975-2006
see:
Pilot Incapacitation 1975-2006
From this document
The results of this study demonstrate that the risk of a pilot suffering from an in-
flight medical condition or incapacitation is low. Such events account for only 0.6
per cent of all the occurrences listed in the ATSB database for the period 1 January
1975 to 31 March 2006. Furthermore, these events account for only 0.19 per cent of
all accidents, 1.0 per cent of all serious incidents, and only 0.05 per cent of all
incidents. The most common cause of the medical event or incapacitation for
affected flights was gastrointestinal illness, usually secondary to food poisoning.
Exposure of the crew to smoke and fumes, and loss of consciousness were the next
most common causes. All fatal accidents occurred in single-pilot operations, where
heart attack in the pilot was the most common cause of the subsequent accident.
Obviously CASA's strict medical policies make the risk of pilot incapacitation extremely small (0.19% of all accidents) because as we all know, pilots are 100% honest with CASA about their medical status and so CASA has been able to remove any pilot who is likely to be incapacitated, from the cockpit.
Imagine the carnage if they weren't so strict! Or heaven forbid, if pilots actually hid things about their medical status from their DAMEs! I know I tell them everything!
That is why every pilot uses their DAME as their GP so that nothing gets unreported.
The majority of pilot incapacitation events recorded by the ATSB do not involve a
chronic or pre-existing medical condition. That is, they are largely unforeseeable
events, often involving acute illnesses or injury. Many are not in themselves life
threatening, but are capable of impairing a pilot’s performance to the extent that
safe operation of the aircraft may be adversely affected. This study also confirms
the findings from other international reports that gastrointestinal illness is the most
common cause of in-flight incapacitation in the pilot population.
Based on the paper, I think CASA's AVMED system would have a huge impact on flight safety if they regularly tested the standard of sandwiches served or snack machines used by flight crew given the largest % of incapacitation is from tummy upsets. This should be the next big area for CASA to be involved in.