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Medical Assessment, several Contracting States permit such applicants to exercise licence privileges,
utilising the flexibility Standard 1.2.4.8, and others may wish to consider doing so. This Appendix
provides guidance to such Authorities. Since the risk to flight safety is greater in Type 1 than in Type 2
insulin-treated diabetic patients, Type 1 applicants should, with currently available treatments and level of
knowledge, be precluded from obtaining a Medical Assessment.
The key areas of concern in certificating aircrew with insulin treated diabetes mellitus are hypoglycaemia
and the enhanced risks of micro- and macrovascular disease. In the paragraphs that follow, the focus will
be on the risks of hypoglycaemia and the protocol at the end of the Appendix will include an assessment
of cardiovascular risk.
2. Risk analysis and literature review
a) Type 1
Any risk assessment requires a review of the literature with reference to the prevalence of hypoglycaemia
in insulin-treated diabetes mellitus. Also required is the application of sound clinical judgement as to
whether one can extrapolate population data to individual cases. It is proposed to discuss the rate of
hypoglycaemia in Type 1 diabetes and then review the differing rates in Type 2 diabetes.
It is very difficult to assess the frequency of hypoglycaemia in insulin-treated diabetic populations
because of the wide variation of severity and outcome. As examples can be mentioned the common
occurrence of asymptomatic biochemical hypoglycaemia, which is only evident if blood glucose is
measured frequently, and the failure to recognize or record many mild episodes including those occurring
during sleep. However, a critical review of the medical literature on the subject provides some data on
which to base a risk assessment. Since the publication of the Diabetes Control and Complication Trial
(DCCT) in Type 1 diabetes, which showed that tight diabetic control could assist in the prevention of
complications, diabetic physicians have striven to improve overall control. However, this study showed
an approximate three-fold increase in prevalence of severe hypoglycaemia in the intensively treated group
compared to that of the conventionally treated (0.54 v 0.17 episodes/patient/year). An analysis of the
cumulative incidence of successive episodes indicated that intensive treatment was also associated with an
increased risk of multiple episodes within the same patient (e.g. 22 per cent experienced five or more
episodes of severe hypoglycaemia within five years of follow-up versus 4 per cent in the conventional
group). Several sub-groups defined by baseline characteristics, including males, adolescents and subjects
with no C-peptide or with a prior history of hypoglycaemia had a particularly high risk of severe
hypoglycaemia in both treatment groups.
Ward and colleagues (1990) found in an out-patient study of 158 patients in Auckland that almost all, 98
per cent, had experienced hypoglycaemic episodes and for 30 per cent these were a major problem. These
ICAO Preliminary Unedited Version — March 2010 III-4A-2
symptoms of hypoglycaemia, which represent a combination of neuroglycopaenia and autonomic neural
stimulation, would be likely to degrade pilot performance. In theory this may be modulated by good
hypoglycaemic awareness and adequate early correction.
The adverse effects of hypoglycaemia on cognitive function, in Type 1 diabetes, have been studied by
Holmes (1983, 1986), Herold (1985) and Pramming (1986). Cox et al (1993) studied this problem in a
driving simulator and found that the degradation in performance, caused by hypoglycaemia, was not
reliably recognized by subjects with Type 1 diabetes. In practice, therefore, it would be unacceptable for a
pilot, who has lack of hypoglycaemic awareness, to fly as this would present a risk to the safety of the
flight. Further work by Cox (2003) comparing Type 1 and Type 2 diabetic individuals and the
relationship to driving mishaps, found that Type 1 diabetic drivers were at increased risk for driving
mishaps but Type 2 diabetic drivers, even on insulin, appeared not to be at higher risk than non-diabetic
individuals. This study adds further weight to the evidence showing a lower risk of hypoglycaemia in
Type 2 diabetic individuals, even those taking insulin.
The risk of severe hypoglycaemia with intensive insulin therapy was further explored in a study by Bott
et al (1997) in 636 Type 1 diabetics. The incidence of severe hypoglycaemia among participants in the
study varied between 0.05 and 0.27 cases per patient per year. In particular, the authors sought to find a
level of haemoglobin A1 that could predict severe hypoglycaemia but there was no linear or exponential
relationship.
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Manual of Civil Aviation Medicine 1(135)
