The association between diabetes and safe driving: A systematic search and review of the literature and cross-reference with the current guidelines

AIMS

We conducted this review to characterize the quality of evidence about associations between diabetes and safe driving and to evaluate how these findings are reflected within current guidelines available to support clinicians and their patients with diabetes.

METHODS

The first stage entailed a systematic search and review of the literature. Evidence surrounding harms associated with diabetes and driving was identified, screened, extracted and appraised for quality utilizing the Newcastle Ottawa Scales (NOS). Next, relevant guidelines regarding driving and diabetes were sourced and summarized. Finally, the identified guidelines were cross-referenced with the results of the systematic search and review.

RESULTS

The systematic search yielded 12,461 unique citations; 52 met the criteria for appraisal. Fourteen studies were rated as 'high', two as 'medium' and 36 as 'low'. Studies with ratings of 'high' or 'medium' were extracted, revealing a body of inconsistent methods and findings. These results, cross-referenced with the guidelines, suggest a lack of agreement and a limited evidence base to justify recommendations.

CONCLUSIONS

The results presented emphasize the need for a better understanding of the impacts of diabetes on safe driving to inform evidence-based guidelines.

Consistent Effects of Hypoglycemia on Cognitive Function in People With or Without Diabetes

OBJECTIVE

Hypoglycemia poses an immediate threat for cognitive function. Due to its association with acute cognitive impairment, the International Hypoglycemia Study Group (IHSG) defines a blood glucose level <3.0 mmol/L as "level 2 hypoglycemia." In the current study we investigated whether having diabetes, type of diabetes, or hypoglycemia awareness moderates this association.

RESEARCH DESIGN AND METHODS

Adults with type 1 diabetes with normal (n = 26) or impaired (n = 21) hypoglycemic awareness or with insulin-treated type 2 diabetes (n = 15) and age-matched control subjects without diabetes (n = 32) underwent a hyperinsulinemic-euglycemic-hypoglycemic glucose clamp (2.80 ± 0.13 mmol/L [50.2 ± 2.3 mg/dL]). At baseline and during hypoglycemia, calculation ability, attention, working memory and cognitive flexibility were measured with the Paced Auditory Serial Addition Test (PASAT) and the Test of Attentional Performance (TAP).

RESULTS

For the whole group, hypoglycemia decreased the mean ± SD proportion of correct answers on the PASAT by 8.4 ± 12.8%, increased reaction time on the TAP Alertness task by 32.1 ± 66.6 ms, and increased the sum of errors and omissions on the TAP Working Memory task by 2.0 ± 5.5 (all P < 0.001). Hypoglycemia-induced cognitive declines were largely irrespective of the presence or type of diabetes, level of symptomatic awareness, diabetes duration, or HbA1c.

CONCLUSIONS

IHSG level 2 hypoglycemia impairs cognitive function in people with and without diabetes, irrespective of type of diabetes or hypoglycemia awareness status. These findings support the cutoff value of hypoglycemia <3.0 mmol/L (<54 mg/dL) as being clinically relevant for most people with diabetes.

Dextrose 50% versus Dextrose 10% or Dextrose Titration for the Treatment of Out-of-Hospital Hypoglycemia: A Systematic Review

INTRODUCTION

Paramedics commonly administer intravenous (IV) dextrose to severely hypoglycemic patients. Typically, the treatment provided is a 25g ampule of 50% dextrose (D50). This dose of D50 is meant to ensure a return to consciousness. However, this dose may cause harm and lead to difficulties regulating blood glucose levels (BGLs) post-treatment. It is hypothesized that a lower concentration, such as 10% dextrose (D10), may improve symptoms while minimizing harm.

METHODS

PubMed, Embase, CINAHL, and Cochrane Central were systematically searched on September 15, 2020. The PRISMA guidelines were followed. GRADE and risk of bias were applied to determine the certainty of the evidence. Primary literature investigating the use of IV dextrose in hypoglycemic diabetic patients presenting to paramedics or the emergency department was included. Outcomes of interest included safety, efficacy (symptom resolution), and BGL.

RESULTS

Of 680 abstracts screened, 51 full-text articles were reviewed, with eleven studies included. Data from three randomized controlled trials (RCTs) and eight observational studies were analyzed. A single RCT comparing D10 to D50 was identified. The primary significant finding of the study was an increased post-treatment glycemic profile by 3.2mmol/L in the D50 group; no other outcomes had significant differences between groups. When comparing pooled data from all the included studies, there was greater symptom resolution in the D10 group (95.9%) compared to the D50 group (88.8%). However, the mean time to resolution was approximately four minutes longer in the D10 group (4.1 minutes [D50] versus 8.0 minutes [D10]). There was a greater need for subsequent doses with the use of D10 (19.5%) compared to D50 (8.1%). The post-treatment glycemic profile was lower in the D10 group at 6.2mmol/L versus 8.5mmol/L in the D50 group. Both treatments had nearly complete resolution of hypoglycemia: 98.7% (D50) and 99.2% (D10). No adverse events were observed in the D10 group (0/1057) compared to 13/310 adverse events in the D50 group.

CONCLUSION

Studies show D10 may be as effective as D50 at resolving symptoms and correcting hypoglycemia. Although the desired effect can take several minutes longer, there appear to be fewer adverse events. The post-D10-treatment BGL may result in fewer untoward hyperglycemic episodes.

Blood glucose monitoring by insulin-treated pilots of commercial and private aircraft: An analysis of out-of-range values

AIM

To examine blood glucose measurements recorded as part of the diabetes protocol operated by the UK, Ireland and Austria, which allows commercial airline pilots with insulin-treated diabetes to fly.

METHODS

An observational study was conducted in pilots with insulin-treated diabetes, granted medical certification to fly commercial or noncommercial aircraft, who recorded pre-flight and hourly in-flight blood glucose measurements. These values were correlated to a traffic light system (green 5.0 to 15.0 mmol/L; amber 4.0 to 4.9 mmol/L and 15.1 to 20.0 mmol/L; and red <4.0 mmol/L or >20.0 mmol/L) and studied for trends in glucose concentrations, time course within flight and any consequences. Pilot demographics were also analysed.

RESULTS

Forty-four pilots (90%) recorded one or more blood glucose value outside the green range during the 7 years of the study. Pilot age, diabetes type and duration, and follow-up period were comparable among subgroups, and mean glycated haemoglobin did not differ before and after certification in a way which would indicate poorer glycaemic control in any subgroup. A total of 892 blood glucose values (2.31%) were outside the green range, with half reported in-flight at various time intervals. There were 48 (0.12%) low red range values recorded, 14 (0.04%) of which occurred in-flight; all but four were restored to within the green range by the time of the next measurement. Appropriate corrective action was taken for all out-of-range values, with no reports of pilot incapacitation from any cause.

CONCLUSIONS

The traffic light system appears effective in identifying and reducing the frequency and severity of out-of-range values.

An Evaluation of the Safety of Pilots With Insulin-Treated Diabetes in Europe Flying Commercial and Noncommercial Aircraft

OBJECTIVE

The risk of hypoglycemia in people with insulin-treated diabetes has debarred them from certain "safety-critical" occupations, including flying commercial aircraft. This report evaluates the effectiveness of a protocol enabling a large cohort of insulin-treated pilots to fly commercially.

RESEARCH DESIGN AND METHODS

This was an observational study of pilots with insulin-treated diabetes who were granted medical certification to fly commercial and noncommercial aircraft. Clinical details, pre- and in-flight (hourly and 30 min before landing) blood glucose values were correlated against the protocol-specified ranges: green (5-15 mmol/L), amber (low, 4-4.9 mmol/L; high, 15.1-20 mmol/L), and red (low, <4 mmol/L; high, >20 mmol/L).

RESULTS

A total of 49 pilots with type 1 (84%) or type 2 (16%) diabetes who had been issued class 1 or class 2 certificates were studied. Median diabetes duration was 10.9 years. Mean HbA_1c was 7.2% (55.0 mmol/mol) before certification and 7.2% (55.1 mmol/mol) after certification (P = 0.97). Blood glucose values (n = 38,621) were recorded during 22,078 flying hours. Overall, 97.69% of measurements were within the green range, 1.42% within the low amber range, and 0.75% within the high amber range. Only 0.12% of readings were within the low red range and 0.02% within the high red range. Out-of-range readings declined from 5.7% in 2013 to 1.2% in 2019. No episodes of pilot incapacitation occurred, and glycemic control did not deteriorate.

CONCLUSIONS

The protocol is practical to implement, and no events compromising safety were reported. This study represents what is, to our knowledge, the most extensive data set from people with insulin-treated diabetes working in a "safety-critical" occupation, which may be relevant when estimating risk in other safety-critical occupations.

The effect of postprandial glycaemia on cognitive function: a randomised crossover trial

The effect on cognitive test scores of generating differences in postprandial glycaemia using test foods or beverages has been inconsistent. Methodological issues may account for some of the variable results requiring further investigation using strong study designs into the relationship between glycaemia and cognitive functioning. The objective of this study was to determine the effects of postprandial glycaemia on cognitive function by examining cognition after consumption of foods that differ only by the rate of digestion of available carbohydrate in a population of young adults. In a double-blind, randomised, crossover trial, sixty-five participants received trifle sweetened either with a higher-glycaemic index (GI) sugar (sucrose; GI 65) or a lower-GI sugar (isomaltulose; GI 34). Cognitive tests were completed prior to trifle consumption, and 60 and 120 min after. There was no between-trifle difference at 60 min in performance on free word recall (0·0 (95 % CI -0·6, 0·5)), short delay word recall (0·0 (95 % CI -0·5, 0·5)), long delay word recall (0·0 (95 % CI -0·6, 0·6)), letter-number sequence recall (0·3 (95 % CI - 0·2, 0·7)) and visuo-spatial recall (-0·2 (95 % CI -0·6, 0·2)) tests. At 120 min, no difference was detected in any of these tests. The participants performed 7·7 (95 % CI 0·5,14·9) s faster in Reitan's trail-making test B 60 min after the higher-GI trifle than the lower-GI trifle (P = 0·037). Our findings of a null effect on memory are generally consistent with other works in which blinding and robust control for confounding have been used.

Cognitive costs of reproduction: life-history trade-offs explain cognitive decline during pregnancy in women

Life-history theory predicts that access to limited resources leads to trade-offs between competing body functions. Women, who face higher costs of reproduction when compared to men, should be especially vulnerable to these trade-offs. We propose the 'cognitive costs of reproduction hypothesis', which states that energy trade-offs imposed by reproduction may lead to a decline in maternal cognitive function during gestation. In particular, we hypothesize that the decline in cognitive function frequently observed during pregnancy is associated with the allocation of resources between the competing energetic requirements of the mother's brain and the developing foetus. Several distinctive anatomical and physiological features including a high metabolic rate of the brain, large infant size, specific anatomical features of the placenta and trophoblast, and the lack of maternal control over glucose flow through the placenta make the occurrence of these trade-offs likely. Herein, we review several lines of evidence for trade-offs between gestation and cognition that are related to: (i) energy metabolism during reproduction; (ii) energy metabolism of the human brain; (iii) links between energy metabolism and cognitive function; and (iv) links between gestation and cognitive function. We also review evidence for the important roles of cortisol, corticotropin-releasing hormone and sex hormones in mediating the effects of gestation on cognition, and we discuss possible neurophysiological mechanisms underlying the observed effects. The evidence supports the view that energy trade-offs between foetal growth and maternal endocrine and brain function lead to changes in maternal cognition, and that this phenomenon is mediated by neuroendocrine mechanisms involving the hypothalamic-pituitary-adrenal axis, brainstem nucleus locus coeruleus and hippocampus.

Effects of hypoglycaemia on working memory and regional cerebral blood flow in type 1 diabetes: a randomised, crossover trial

AIMS/HYPOTHESIS

The aim of this randomised, crossover trial was to compare cognitive functioning and associated brain activation patterns during hypoglycaemia (plasma glucose [PG] just below 3.1 mmol/l) and euglycaemia in individuals with type 1 diabetes mellitus.

METHODS

In this patient-blinded, crossover study, 26 participants with type 1 diabetes mellitus attended two randomised experimental visits: one hypoglycaemic clamp (PG 2.8 ± 0.2 mmol/l, approximate duration 55 min) and one euglycaemic clamp (PG 5.5 mmol/l ± 10%). PG levels were maintained by hyperinsulinaemic glucose clamping. Cognitive functioning was assessed during hypoglycaemia and euglycaemia conditions using a modified version of the digit symbol substitution test (mDSST) and control DSST (cDSST). Simultaneously, regional cerebral blood flow (rCBF) was measured in pre-specified brain regions by six H₂¹⁵O-positron emission tomographies (PET) per session.

RESULTS

Working memory was impaired during hypoglycaemia as indicated by a statistically significantly lower mDSST score (estimated treatment difference [ETD] -0.63 [95% CI -1.13, -0.14], p = 0.014) and a statistically significantly longer response time (ETD 2.86 s [7%] [95% CI 0.67, 5.05], p = 0.013) compared with euglycaemia. During hypoglycaemia, mDSST task performance was associated with increased activity in the frontal lobe regions, superior parietal lobe and thalamus, and decreased activity in the temporal lobe regions (p < 0.05). Working memory activation (mDSST - cDSST) statistically significantly increased blood flow in the striatum during hypoglycaemia (ETD 0.0374% [95% CI 0.0157, 0.0590], p = 0.002).

CONCLUSIONS/INTERPRETATION

During hypoglycaemia (mean PG 2.9 mmol/l), working memory performance was impaired. Altered performance was associated with significantly increased blood flow in the striatum, a part of the basal ganglia implicated in regulating motor functions, memory, language and emotion.

TRIAL REGISTRATION

NCT01789593, clinicaltrials.gov FUNDING: This study was funded by Novo Nordisk.

The risks of nocturnal hypoglycaemia in insulin-treated diabetes

Over half of all episodes of severe hypoglycaemia (requiring external help) occur during sleep, but nocturnal hypoglycaemia is often asymptomatic and unrecognised. The precise incidence of nocturnal hypoglycaemia is difficult to determine with no agreed definition, but continuous glucose monitoring has shown that it occurs frequently in people taking insulin. Attenuation of the counter-regulatory responses to hypoglycaemia during sleep may explain why some episodes are undetected and more prolonged, and modifies cardiovascular responses. The morbidity and mortality associated with nocturnal hypoglycaemia is probably much greater than realised, causing seizures, coma and cardiovascular events and affecting quality of life, mood and work performance the following day. It may induce impaired awareness of hypoglycaemia. Cardiac arrhythmias that occur during nocturnal hypoglycaemia include bradycardia and ectopics that may provoke dangerous arrhythmias. Treatment strategies are discussed that may help to minimise the frequency of nocturnal hypoglycaemia.

Emergency treatment of hypoglycaemia: a guideline and evidence review

AIM

To examine the current treatment guidelines for the emergency management of hypoglycaemia and the evidence underpinning recommendations.

METHODS

International diabetes agencies were searched for hypoglycaemia treatment guidelines. Guidelines were assessed using the Appraisal of Guidelines Research and Evaluation II (AGREE II) instrument. An electronic database search was conducted for evidence regarding emergency treatment of hypoglycaemia in adults, and relevant articles were critically appraised.

RESULTS

Of the international diabetes agencies, six sets of guidelines were deemed relevant and of sufficient detail for appraisal by AGREE II. The evidence search returned 2649 articles, of which 17 pertaining to the emergency management of hypoglycaemia were included. High-quality evidence for the management of hypoglycaemia was lacking, limiting treatment recommendations. In general, guidelines and studies were somewhat concordant and recommended 15-20 g of oral glucose or sucrose, repeated after 10-15 min for treatment of the responsive adult, and 10% intravenous dextrose or 1 mg intramuscular glucagon for treatment of the unresponsive adult. No evidence was found for other treatment approaches.

CONCLUSION

Evidence for the emergency treatment of hypoglycaemia in adults is limited, is often low grade and mostly pre-dates contemporary management of diabetes. Guideline recommendations are limited by the lack of randomized trials. Further high-quality studies are required to inform the optimum management of this frequently occurring emergency condition.

Severe hypoglycemia, impaired awareness of hypoglycemia, and self-monitoring in adults with type 1 diabetes: Results from Diabetes MILES-Australia

AIMS

To assess prevalence of severe hypoglycemia, awareness and symptoms of hypoglycemia, and their associations with self-monitoring of blood glucose.

METHODS

Diabetes MILES-Australia Study participants completed validated questionnaires and study-specific items.

RESULTS

Of 642 adults with type 1 diabetes, 21% reported ≥1 severe hypoglycemic event in the past six months, and 21% reported impaired awareness of hypoglycemia (IAH). Severe hypoglycemia was increased four-fold for those with IAH compared with intact awareness (1.4±3.9 versus 0.3±1.0). Of those with IAH, 92% perceived autonomic and 88% neuroglycopenic symptoms, albeit at lower glucose thresholds compared to people with intact awareness. Those with IAH were more likely to perceive both symptom types at the same glucose level or to perceive neuroglycopenic symptoms first (all p<0.001). Eighteen percent with IAH treated hypoglycemia only when they perceived symptoms and another 18% only when their capillary glucose was <3.0mmol/L.

CONCLUSIONS

One in five adults with type 1 diabetes had IAH or experienced severe hypoglycemia in the past sixmonths. Total loss of hypoglycemia symptoms was rare; most people with IAH retained autonomic symptoms, perceived at relatively low glucose levels. Frequent self-monitoring of blood glucose prompted early recognition and treatment of hypoglycemia, suggesting severe hypoglycemia risk can be minimized.

Effects of Sleep Deprivation on Hypoglycemia-Induced Cognitive Impairment and Recovery in Adults With Type 1 Diabetes

OBJECTIVE

To ascertain whether hypoglycemia in association with sleep deprivation causes greater cognitive dysfunction than hypoglycemia alone and protracts cognitive recovery after normoglycemia is restored.

RESEARCH DESIGN AND METHODS

Fourteen adults with type 1 diabetes underwent a hyperinsulinemic, hypoglycemic clamp on two separate occasions. Before one glucose clamp, the participants stayed awake overnight to induce sleep deprivation. Participants were randomized and counterbalanced to the experimental condition. Cognitive function tests were performed before and during hypoglycemia and for 90 min after restoration of normoglycemia.

RESULTS

Cognitive impairment during hypoglycemia did not differ significantly between the sleep-deprived and non-sleep-deprived conditions. However, in the sleep-deprived state, digit symbol substitution scores and choice reaction times were significantly poorer during recovery (P < 0.001) and hypoglycemia symptom scores were significantly higher (P < 0.001), even when symptoms that may have been caused by sleep deprivation, such as tiredness, were removed.

CONCLUSIONS

Hypoglycemia per se produced a significant decrement in cognitive function; coexisting sleep deprivation did not have an additive effect. However, after restoration of normoglycemia, preceding sleep deprivation was associated with persistence of hypoglycemic symptoms and greater and more prolonged cognitive dysfunction during the recovery period.

Brain glucose metabolism during hypoglycemia in type 1 diabetes: insights from functional and metabolic neuroimaging studies

Hypoglycemia is the most frequent complication of insulin therapy in patients with type 1 diabetes. Since the brain is reliant on circulating glucose as its main source of energy, hypoglycemia poses a threat for normal brain function. Paradoxically, although hypoglycemia commonly induces immediate decline in cognitive function, long-lasting changes in brain structure and cognitive function are uncommon in patients with type 1 diabetes. In fact, recurrent hypoglycemia initiates a process of habituation that suppresses hormonal responses to and impairs awareness of subsequent hypoglycemia, which has been attributed to adaptations in the brain. These observations sparked great scientific interest into the brain's handling of glucose during (recurrent) hypoglycemia. Various neuroimaging techniques have been employed to study brain (glucose) metabolism, including PET, fMRI, MRS and ASL. This review discusses what is currently known about cerebral metabolism during hypoglycemia, and how findings obtained by functional and metabolic neuroimaging techniques contributed to this knowledge.

Driving and diabetes: problems, licensing restrictions and recommendations for safe driving

Driving is a complex process that places considerable demands on cognitive and physical functions. Many complications of diabetes can potentially impair driving performance, including those affecting vision, cognition and peripheral neural function. Hypoglycemia is a common side-effect of insulin and sulfonylurea therapy, impairing many cognitive domains necessary for safe driving performance. Driving simulator studies have demonstrated how driving performance deteriorates during hypoglycemia. Driving behavior that may predispose to hypoglycemia while driving is examined. Studies examining the risk of road traffic accidents in people with insulin-treated diabetes have produced conflicting results, but the potential risk of hypoglycemia-related road traffic accidents has led to many countries imposing restrictions on the type and duration of driving licenses that can be issued to drivers with diabetes. Guidance that promotes safe driving practice has been provided for drivers with insulin-treated diabetes, which is the group principally addressed in this review.

The Impact of Diabetes on Cerebral Structure and Function

Diabetes alters cerebral metabolism, structure, and function. Both hyperglycemia and therapy-associated hypoglycemia are believed to have an impact on the brain, and this impact may depend on the age of the individual, their stage of neurological development, and whether they have Type 1 or Type 2 diabetes. Hypoglycemia in children with Type 1 has consistently been associated with a reduction in neurocognitive function, but such a finding has not been seen in adults with Type 1 diabetes. Both hypoglycemia and hyperglycemia have been linked with dementia in adults with Type 2 diabetes. In both Type 1 and Type 2 diabetes, recurrent episodes of treatment-associated hypoglycemia impair how well the brain can sense and respond to subsequent episodes of hypoglycemia. In this brief review, we will review how diabetes affects the brain with a focus on investigations done in our own laboratory. We have focused on using high magnetic field imaging and spectroscopy to identify subtle changes in brain structure and metabolism that may contribute to the long-term cerebral complications of diabetes. We have found evidence of microstructural changes in white matter regions, reduced gray matter density, and reduced activation of the thalamus in response to recurrent hypoglycemia in patients with Type 1 diabetes.

Basal insulin secretion, PCL-R and recidivism among impulsive violent alcoholic offenders

Current risk assessment tools have a moderate predicting value for violence. Their power may be enhanced with certain biological indicators, which may serve as predictors of recidivistic violence itself. The aim of our study was to determine the strength of serum insulin levels to predict violence, and compare these results with those from the Revised Psychopathy Checklist (PCL-R). The study population consisted of 105 Finnish alcoholics who were severely violent offenders, recruited from 1991 to 1998. After exclusion, 75 cases were followed until March 2008, or until a new offense was registered. Cox regression analysis was used to evaluate the risk of recidivism. The age and weight adjusted effect of insulin to recidivism risk showed a 7.2% increase for each International Unit (IU), or 19% for the mean difference (2.5IU) between recidivists and non-recidivist, which corresponds to a medium effect size (Cohen׳s d=0.46). Adjusting the insulin model with PCL-R factor 1 enhanced the predictive power slightly. Serum fasting insulin level was equivalent to the PCL-R factor 2 score as a predictor, and better than the total PCL-R score. However, the significance of these results was too low for predicting recidivism in the process of judicial decision-making.

Hypoglycaemia in diabetes mellitus: epidemiology and clinical implications

Hypoglycaemia is a frequent adverse effect of treatment of diabetes mellitus with insulin and sulphonylureas. Fear of hypoglycaemia alters self-management of diabetes mellitus and prevents optimal glycaemic control. Mild (self-treated) and severe (requiring help) hypoglycaemia episodes are more common in type 1 diabetes mellitus but people with insulin-treated type 2 diabetes mellitus are also exposed to frequent hypoglycaemic events, many of which occur during sleep. Hypoglycaemia can disrupt many everyday activities such as driving, work performance and leisure pursuits. In addition to accidents and physical injury, the morbidity of hypoglycaemia involves the cardiovascular and central nervous systems. Whereas coma and seizures are well-recognized neurological sequelae of hypoglycaemia, much interest is currently focused on the potential for hypoglycaemia to cause dangerous and life-threatening cardiac complications, such as arrhythmias and myocardial ischaemia, and whether recurrent severe hypoglycaemia can cause permanent cognitive impairment or promote cognitive decline and accelerate the onset of dementia in middle-aged and elderly people with diabetes mellitus. Prevention of hypoglycaemia is an important part of diabetes mellitus management and strategies include patient education, glucose monitoring, appropriate adjustment of diet and medications in relation to everyday circumstances including physical exercise, and the application of new technologies such as real-time continuous glucose monitoring, modified insulin pumps and the artificial pancreas.

Management of Type 1 Diabetes in Older Adults

Older adults with type 1 diabetes are at high risk for severe hypoglycemia and may have serious comorbid conditions. Problems with cognition, mobility, dexterity, vision, hearing, depression, and chronic pain interfere with the ability to follow complex insulin regimens. With the development of geriatric syndromes, unpredictable eating, and frailty, treatment regimens must be modified with the goal of minimizing hypoglycemia and severe hyperglycemia and maximizing quality of life.

Diabetes and driving

The principal safety concern for driving for people treated with insulin or insulin secretagogues is hypoglycaemia, which impairs driving performance. Other complications, such as those causing visual impairment and peripheral neuropathy, are also relevant to medical fitness to drive. Case control studies have suggested that drivers with diabetes pose a modestly increased but acceptable and measurable risk of motor vehicle accidents compared to non-diabetic drivers, but many studies are limited and of poor quality. Factors which have been shown to increase driving risk include previous episodes of severe hypoglycaemia, previous hypoglycaemia while driving, strict glycaemic control (lower HbA1c) and absence of blood glucose monitoring before driving. Impaired awareness of hypoglycaemia may be counteracted by frequent blood glucose testing. The European Union Third directive on driving (2006) has necessitated changes in statutory regulations for driving licences for people with diabetes in all European States, including the UK. Stricter criteria have been introduced for Group 1 vehicle licences while those for Group 2 licences have been relaxed. Insulin-treated drivers can now apply to drive Group 2 vehicles, but in the UK must meet very strict criteria and be assessed by an independent specialist to be issued with a 1-year licence.