Hypoglycaemia in Clinical Diabetes

318 LIVING WITH HYPOGLYCAEMIAfor public safety, much lay, and even medical, ignorance exists about hypoglycaemiaand its effects, so that discriminatory practices still occur, particularly with regard toemployment.Effect of Hypoglycaemia on DrivingDriving is a common and everyday activity that demands complex psychomotor skills,including good visuo-spatial functions, rapid information processing, vigilance and satisfactoryjudgment. Because hypoglycaemia rapidly interferes with cognitive functions, evenmodest degrees of neuroglycopenia may affect driving skills, without necessarily provokingsymptomatic awareness of hypoglycaemia. Seminal studies using a sophisticated drivingsimulator have examined the driving abilities of drivers with type 1 diabetes at different bloodglucose concentrations, maintained by a glucose clamp (Cox et al., 1993; Cox et al., 2000).Driving performance started to deteriorate when blood glucose declined below 3.8 mmol/l,and typical driving deficiencies included speeding and inappropriate braking, driving offthe road, crossing the centre line, ignoring ’STOP’ signs and causing an increased numberof ‘crashes’. Allowing for the artificial conditions of a driving simulator, it is evident thathypoglycaemia has an adverse effect on driving performance. A particularly disconcertingobservation in these studies was that none of the drivers took action to treat hypoglycaemiauntil their blood glucose had declined to < 28 mmol/l, and then only 30% of the participantsresponded (Cox et al., 2000). Many of the drivers did not experience any warning symptomsof hypoglycaemia, and fewer than 25% said they did not feel competent to drive whentheir blood glucose was low (Cox et al., 1993; Cox et al., 2000). The driving simulatorstudies also demonstrated that driving has a substantial metabolic demand that can lowerblood glucose (Cox et al., 2001, Cox et al., 2002), leading the authors to recommend thata prophylactic snack should be consumed before driving if blood glucose is 5.0 mmol/l orless. Various studies have shown that many drivers with insulin-treated diabetes believethat it is safe to drive when their blood glucose is low (Weinger et al., 1999; Clarkeet al., 1999; Graveling et al., 2004); this misperception may be influenced by progressiveneuroglycopenia.Hypoglycaemia can impair cognitive function and judgment without necessarily provokingwarning symptoms or altering consciousness. Driving can therefore continue while apparentlynot being under conscious control, a condition which is given the strictly legal term of‘automatism’ (there are no medical publications about ‘automatism’), and irrational andcompulsive behaviour during hypoglycaemia has been described by insulin-treated diabeticdrivers (Frier et al., 1980). The police, suspecting alcohol and inebriation to be the cause ofa driver’s altered behaviour and symptoms, have on occasion arrested diabetic drivers whoare hypoglycaemic.Risk of Accidents and Restriction of Driving LicencesHypoglycaemia can adversely affect the ability to drive, and in individual cases hypoglycaemiahas been implicated as a precipitating cause of road traffic accidents, causing theoccasional fatality. In a study of insulin-treated drivers in Northern Ireland, the number ofhypoglycaemic episodes that occurred while driving in the preceding year was shown to beassociated with the total number of accidents during the previous five years (Stevens et al.,