Motor vehicle accidents and IDDM

Does gender affect the driving performance of young patients with diabetes?

Recent evidence suggests that poor glycemic control among young patients with type 1 diabetes mellitus (T1DM) has negative cognitive and physical effects, whose extent is gender-dependent. For example, female patients with diabetes present more physical and cognitive limitations than male patients in terms of cognitive adjustment, quality of decision making, and functioning. Studies about traffic safety report that diabetic drivers are at increased risk of being involved in road crashes, especially when driving in a state of hypoglycemia under which their blood glucose level is too low. We have recently demonstrated that acute hyperglycemia (when the blood glucose level is too high) can also lead to poor driving performance among T1DM young adult patients. Against this background, the objective of the present study was to find out whether gender affects the driving performance of young drivers with diabetes. Twenty-six T1DM drivers participated in a counterbalanced crossover experiment. While being monitored by an eye tracker, they drove a driving simulator and twice navigated through the nine hazardous scenarios: once under a normal blood glucose (euglycemia) level and once high blood glucose (hyperglycemia) level. The first main result is that young female drivers are more affected by diabetes than young male drivers, regardless of momentary glycemic changes. The second main result is that poor glycemic control substantially deteriorates hazard perception and driving performance of young males with diabetes. Thus, it is argued that an uncontrolled state of a high blood glucose level may be more hazardous for young males with diabetes since it negatively impacts their driving performance.

Attitudes to driving among patients with diabetes mellitus in Punjab (ADD-Punjab study)

AIM

Currently there are no regulations regarding diabetes and driving licensing in India. The study was planned to gather information about attitudes to driving among patients with diabetes mellitus.

METHODS

Adult patients with diabetes mellitus holding a current valid driving license on treatment with insulin or secretagogue were interviewed using a validated structured questionnaire.

RESULTS

150 patients were interviewed with a mean age of 52 years, males (86%), insulin users (34%) and only secretagogue users (66%). 16 (10.6%) patients had severe hypoglycemia in the past year with 9.3% having hypoglycemic unawareness. Only 32% patients were aware of the relation between hypoglycemia and driving, 88.6% never checked glucose prior to driving and only 23% patients carried carbohydrates for treatment of hypoglycemia during driving. 25 (16.7%) of subjects had hypoglycemia during driving and in 6 (4%) this involved a traffic accident in the past one year.

CONCLUSIONS

Around 4% of patients on hypoglycemia causing treatment have a traffic accident/event every year. In the absence of regulations currently, focus should be on patient education. However, on the long-term appropriate regulations will make the roads safer for patients with diabetes.

Diabetes and collision risk. A meta-analysis and meta-regression

AIMS

The main objective of this study was to see whether diabetes is associated with an increased collision risk and to test the effect of age and gender on the overall collision risk for diabetes drivers.

MATERIALS AND METHODS

Twenty-eight studies were included in meta-analysis, using mean age, gender, continent and the prevalence of fatal road incidents as covariates.

RESULTS

The collision risk for diabetes drivers was small and not statistically significant - RR = 1.11 (1.01-1.23) with a prediction interval (PI) or 0.77-1.65. Age and gender were not associated with an increased overall risk. Insulin-dependent diabetes patients had a slightly increased effect size compared with the overall diabetes population, but the effect was not statistically significant. European diabetes drivers had a lower collision risk compared with their North American counterparts, the main cause being the difference of collision risk in the countries in which the studies were performed.

CONCLUSIONS

Overall, diabetes patients do not have a statistically significant increased risk for unfavourable traffic events. Old age and insulin-dependent patients tend to have a higher risk. Advances in diabetes care, associated with advances in road safety regulations, and automotive industry have not decreased significantly the collision risk in the last 50 years for drivers with diabetes.

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.

Road traffic accident risk in patients with diabetes mellitus receiving blood glucose-lowering drugs. Prospective follow-up study

AIM

To investigate, at a national level, whether patients using insulin or oral glucose-lowering agents had an increased risk of road traffic accidents compared with non-users.

METHODS

All Norwegians aged 18-69 years (3.1 million) were followed from April 2004 until September 2006. Information on drug prescriptions, road traffic accidents and emigration/death was obtained from the following population-based registries: the Prescription Database, the Road Accident Registry and the Central Population Registry. The exposure period was the time from the first prescription of insulin or oral glucose-lowering agent during the study period. The incidence of accidents in the exposed person-time was compared with the incidence of accidents in the unexposed person-time by standardized incidence ratio (SIR).

RESULTS

During the study period, 20 494 road traffic accidents with personal injuries were registered in Norway. One hundred and eighty-three accidents were registered for insulin users not taking oral glucose-lowering agents and 219 for users of oral blood glucose-lowering drugs without insulin. The SIR (95% confidence interval) for all ages and both genders combined were: insulin 1.4 (1.2-1.6), oral glucose-lowering agents 1.2 (1.0-1.3) and users of drugs for peptic ulcer and gastro-oesophageal reflux disease (negative comparators) 1.3 (1.2-1.4). The highest SIRs were found among the youngest insulin users (18-34 years old).

CONCLUSIONS

A slightly increased risk of being involved in a road traffic accident was observed for drivers prescribed insulin, while no increased risk was observed for drivers prescribed oral glucose-lowering agents. The increased risk observed for insulin users was similar to that observed for users of drugs for peptic ulcer and gastro-oesophageal reflux disease.

Road traffic accidents and diabetes: insulin use does not determine risk

AIMS

Progressive restrictions placed on insulin-treated patients with diabetes exclude them from driving group 2 and class C1 and D1 vehicles. This reflects an assumption that an increased risk of hypoglycaemia in these patients will cause road traffic accidents. These restrictions have been implemented without any consistent evidence that this is the case. The aim of the study was therefore to investigate whether the rate of road traffic collisions in insulin-treated patients was higher than that of the non-diabetic population using a population register-based study.

METHODS

A historical cohort study combined information from the Devon and Cornwall Constabulary database on road traffic collisions with the district wide retinal screening database, to provide an anonymized matched database of road traffic collisions in the diabetic population. Accident rates were calculated in the diabetic population and compared to rates in the non-diabetic population using relative risks.

RESULTS

The estimated overall annual accident rate for the non-diabetic population was 1469 per 100,000 vs. 856 per 100,000 for the diabetic population as a whole (Chi-squared, P < 0.001). On stratification of the groups by age, within the insulin-treated group there was no significant difference in the accident rate compared to the non-diabetic population, with relative risks between 0.51 [confidence interval (CI) 0.25-1.05] and 1.13 (CI 0.88-1.46).

CONCLUSIONS

Our findings suggest that insulin-treated patients as a group do not pose an increased risk to road safety. They reiterate the need for an individualized risk-based assessment when considering driving restrictions.

Mortality in childhood-onset type 1 diabetes: a population-based study

OBJECTIVE

To describe the age- and sex-specific mortality in a cohort of young type 1 diabetic patients and to analyze the causes of death with special focus on suicide, accidents, and unexplained deaths.

RESEARCH DESIGN AND METHODS

A population-based incident childhood diabetes register, covering onset cases since 1 July 1977, was linked to the Swedish Cause of Death Register up to 31 December 2000. The official Swedish population register was used to calculate age- and sex-standardized mortality rates (SMRs), excluding neonatal deaths. To analyze excess risks for specific diagnoses, case subjects were compared with five nondiabetic control subjects, matched by age, sex, and year of death. Death certificates were collected for all case and control subjects. For case subjects with an unclear diagnosis, hospital records and/or forensic autopsy reports were obtained.

RESULTS

Mean age- and sex-SMR was 2.15 (95% CI 1.70-2.68) and tended to be higher among females (2.65 vs. 1.93, P = 0.045). Mean age at death was 15.2 years (range 1.2-27.3) and mean duration 8.2 years (0-20.7). Twenty-three deaths were clearly related to diabetes; 20 died of diabetic ketoacidosis. Only two case subjects died with late diabetes complications (acute coronary infarction). Thirty-three case subjects died with a diagnosis not directly related to diabetes; 7 of them committed suicide, and 14 died from accidents. There was no significant difference in traffic accidents (odds ratio 1.02 [95% CI 0.40-2.37]). Obvious suicide tended to be increased but not statistically significantly so (1.55 [0.54-3.89]). Seventeen diabetic case subjects were found deceased in bed without any cause of death found at forensic autopsy. Only two of the control subjects died of similar unexplained deaths.

CONCLUSIONS

In a well-developed health care system, there is still a significant excess mortality in young type 1 diabetic patients. We confirm a very large proportion of unexplained deaths in bed, which should be further studied. There is no clear excess death rate caused by suicide or traffic accidents among young diabetic subjects.

Hypoglycaemia and driving in people with insulin-treated diabetes: adherence to recommendations for avoidance

BACKGROUND

Hypoglycaemia impairs driving performance, so drivers with insulin-treated diabetes should try to avoid hypoglycaemia when driving, and treat it effectively if it occurs. It is not known how many insulin-treated drivers are familiar with, or adhere to, recommended safe practice.

METHODS

We surveyed a representative sample of 202 current drivers with insulin-treated diabetes (115 with Type 1 diabetes), using a structured questionnaire. Data were obtained on driving history, estimated frequency of hypoglycaemia, and measures taken to avoid and treat hypoglycaemia when driving.

RESULTS

The licensing authority (DVLA) and motor insurance company had been informed by almost all participants. Sixty-four participants (31.7%) had experienced hypoglycaemia while driving, and 27 (13.4%) reported that this had occurred within the preceding year. A minimum blood glucose level of 4.0 mmol/l or higher was considered necessary for driving by 151 drivers (74.8%), and 176 (87.1%) reported always keeping carbohydrate in their vehicle. However, 77 (38.1%) reported never carrying a glucose meter when driving, and 121 (59.9%) that they never test blood glucose before driving, or test only if symptomatic of hypoglycaemia. Most participants (89%) would stop driving to treat hypoglycaemia and would not resume driving immediately, although only 28 (13.9%) would wait longer than 30 min. Almost half of participants were failing to observe at least one essential aspect of safe driving.

CONCLUSIONS

Compliance with statutory requirements to inform the licensing authority and motor insurer is good, and drivers' perceptions of the minimum safe blood glucose level for driving are encouraging. However, most drivers rely on symptoms to detect hypoglycaemia while driving, and seldom test blood glucose before driving. Patient education should emphasize the role of blood glucose monitoring in relation to driving, and highlight the potential deterioration in driving performance when blood glucose falls below 4.0 mmol/l.

Diabetes and driving mishaps: frequency and correlations from a multinational survey

OBJECTIVE

The intensive treatment of diabetes to achieve strict glycemic control is a common clinical goal, but it is associated with an increased incidence of hypoglycemia. Becoming hypoglycemic while driving is a hazardous condition and may lead to a greater incidence of driving mishaps. This study investigated whether diabetes is associated with increased risk of driving mishaps and correlates of such a relationship.

RESEARCH DESIGN AND METHODS

During routine visits to diabetes specialty clinics in seven U.S. and four European cities, consecutive adults with type 1 diabetes, type 2 diabetes, and nondiabetic spouse control subjects (n = 341, 332, and 363, respectively) completed an anonymous questionnaire concerning diabetes and driving.

RESULTS

Type 1 diabetic drivers reported significantly more crashes, moving violations, episodes of hypoglycemic stupor, required assistance, and mild hypoglycemia while driving as compared with type 2 diabetic drivers or spouse control subjects (P < 0.01-0.001). Type 2 diabetic drivers had driving mishap rates similar to nondiabetic spouses, and the use of insulin or oral agents for treatment had no effect on the occurrence of driving mishaps. Crashes among type 1 diabetic drivers were associated with more frequent episodes of hypoglycemic stupor while driving, less frequent blood glucose monitoring before driving, and the use of insulin injection therapy as compared with pump therapy. One-half of the type 1 diabetic drivers and three-quarters of the type 2 diabetic drivers had never discussed hypoglycemia and driving with their physicians.

CONCLUSIONS

Type 1 diabetic drivers are at increased risk for driving mishaps, but type 2 diabetic drivers, even on insulin, appear not to be at a higher risk than nondiabetic individuals. Clinical and treatment factors appear to increase risk, e.g., more frequent hypoglycemia while driving, method of insulin delivery, and infrequent self-testing before driving. Physicians are encouraged to talk to their type 1 diabetic patients about hypoglycemia and driving.

Insulin-treated diabetes and driving in the UK

Diabetes, and particularly insulin-treated diabetes, has important implications for motor vehicle driving, largely because of its association with potential hypoglycaemia. For this reason, most countries operate some driving restrictions on insulin-treated diabetic patients, as well as systems of intermittent reassessment of hypoglycaemic risk. In the UK, regulations are operated by the Driver and Vehicle Licensing Agency (DVLA), which is an agency of the Department of the Environment, Transport and the Regions (DETR). They are supported by an Expert Panel which advises the Secretary of State on diabetes-related issues relating to fitness to drive. The patient organization Diabetes UK is also concerned with diabetes and driving issues, largely from a position of lobbying policy-influencers and supporting individual cases. All parties involved with diabetes and driving issues recognize the need for more research on the subject, as the current literature is flawed in design, though no convincing excess of accidents amongst diabetic drivers has been conclusively demonstrated. Currently in the UK, Class 2 vehicles (large trucks and passenger vehicles) are barred to diabetic drivers on insulin. European law has recently extended this to so-called C1 (large vans and small lorries) and D1 (minibuses) vehicles, though the law has recently been revised to allow individual consideration for potential diabetic C1 drivers on insulin treatment. Diabetes and insulin-treated diabetes is an emotive and difficult issue, for which a stronger evidence base is urgently needed.

Accidents in patients with insulin-treated diabetes: increased risk of low-impact falls but not motor vehicle crashes--a prospective register-based study

BACKGROUND

Patients with diabetes mellitus may be at increased risk of accidents, mainly because of hypoglycemia. A variety of approaches have been adopted in an attempt to quantify this risk, but there has not been, to date, a systematic study using a national trauma register. In this study, we report findings from the Scottish Trauma Audit Group database.

METHODS

The database includes all patients admitted to hospital for 3 or more days, or who died in hospital as a result of their accident. The study includes 11,244 cases aged 15 years or over entered into the database between July 1996 and June 1998. This included 151 patients with insulin-treated diabetes. Using detailed prescribing information from one representative region, we have calculated the rates of different types of accidents for patients treated with insulin and compared this with the control population. We have analyzed information on the mechanism and severity of injury, outcome, and length of hospital stay.

RESULTS

Overall, the rate of accidents for insulin-treated patients was estimated at 291.2 per 100,000 population per year compared with 148.4 for the control population (p < 0.001; relative risk, 1.97; 95% confidence interval, 1.68-2.32). Insulin-treated patients were, on average, older (p < 0.005), more likely to be women (p < 0.02), and had longer stay in hospital (p < 0.001). The major excess of injuries related to low falls (< 2 m), which accounted for 62.3% of the injuries in the insulin-treated group compared with 47.1% in the remainder (p < 0.01). Low falls in the insulin-treated group (n = 94) were examined in detail: compared with the control population, there was no difference in age and sex, Injury Severity Score, Revised Trauma Score (a measure of the severity of physiologic disturbance), or calculated probability of survival (TRISS). Length of inpatient stay was higher in the insulin-treated low-fall patients (10 vs. 7 days, p < 0.01). Of the 151 catalogued injuries, the vast majority were fractures at peripheral sites. Only 23 insulin-treated individuals were admitted after a motor vehicle crash during the study period. This represents a slight but not significant increase above the rate for the background population.

CONCLUSION

This study confirms that patients taking insulin are at increased risk of accidents. Among the different types of injury, only low-impact falls were significantly increased. This is most likely related to an increased tendency for insulin-treated patients to fall during a hypoglycemic episode. However, patients with diabetes may also be at higher risk of sustaining a fracture after a fall. The number of car crashes involving drivers with insulin-dependent diabetes is small, and the rate is not significantly greater than that of the background population. Further study of the causes and consequences of falls in diabetic patients is warranted.

Driving and insulin--consensus, conflict or confusion?

AIMS

All drivers requiring insulin treatment must be able to demonstrate satisfactory diabetic control and recognition of hypoglycaemic symptoms before being allowed to drive a motor vehicle. Clinicians have a duty to discuss fitness to drive with their patients. However, is the advice given consistent and in line with the regulations published by the Driver and Vehicle Licensing Authority (DVLA)?

METHODS

Six 'real-life' case scenarios were posted to clinicians (consultant diabetologists, specialist registrars and diabetes specialist nurses) within Wessex, UK. The identical cases were also sent to the DVLA for their comments.

RESULTS

Sixty-six doctors (36 consultants) and 70 diabetes specialist nurses were contacted by postal questionnaire of which replies were received from 17 consultants (47%), 17 specialist registrars (57%) and 39 diabetes specialist nurses (56%). Although there was general agreement in cases of hypoglycaemia unawareness, there was disagreement where patients had or were at risk of unstable control albeit for a short time.

CONCLUSIONS

Patients treated with insulin may receive conflicting information concerning their ability to drive.

Vision impairment and driving

Driving is the primary mode of travel in many countries. It facilitates the performance of routine daily activities and is thus integral with the concept of quality of life. Vision is inarguably a fundamental component of safe driving. Drivers with certain eye conditions reduce their driving exposure and restrict their driving to the safest times, yet there is preliminary evidence that some eye conditions increase the risk of crashes. Visual acuity is only weakly related to crash involvement, whereas peripheral vision appears to play a more critical role. Color vision deficiency by itself is not a threat to safe driving. Based on the current literature, it is unclear whether other types of visual sensory impairment have a significant impact on driving safety and performance. Tests of visual attention and processing speed show great promise as methods of identifying high-risk drivers. There is a serious need for well-designed studies in key practical areas, such as the safety of low-vision drivers who use bioptic telescopes, the impact of monocular vision impairment on safety, and the effectiveness of vision rescreening policies after initial licensure. For ophthalmologists to guide patients about driving fitness, valid and reliable assessment tools must be developed and made widely available.

Diabetes and driving: towards equitable, evidence-based decision-making

In January 1998, the British government introduced new restrictions on licensing of people with insulin-treated diabetes mellitus to drive. These restrictions were based on the second EU driver licensing directive (91/4389) and looked to be costing insulin-treated diabetic individuals their entitlement to drive light goods and small passenger-carrying vehicles. In response to concerns expressed by the diabetes community in Britain, the British Diabetic Association commissioned a report examining and interpreting the available evidence of accident risk in insulin-treated diabetic patients, particularly that related to unexpected hypoglycaemia. The following article is drawn from that report.

Age-specific patterns of factors related to fatal motor vehicle traffic crashes: focus on young and elderly drivers

This population-based study examines patterns of fatal motor vehicle traffic crashes (MVTCs) by age group (16-24, 25-64, 65+) among Canadian drivers. The Canadian Traffic Accident Information Databank (TRAID) provided information about fata MVTCs between 1984 and 1993. Distribution of risk factors was compared by age group. Crude odds ratios and 95% CIs were calculated for both young and elderly drivers compared with middle-aged drivers. The middle-age group was selected as reference population since it demonstrates the lowest risk of fatality. Compared to the middle-aged group, young drivers demonstrated excess risk for (1) risk-taking behaviours and conditions, specifically alcohol and illicit drug use, speeding, non use of seat belts, fatigue and falling asleep, and inexperience; (2) crashes during the summer, during weekends and at night; and (3) single-vehicle collisions and on performing overtaking manoeuvres. Excess risk among elderly drivers was noted for (1) medical and physical conditions, inattention and inexperience; (2) driver actions, for example, improper turning, failure to yield right-to-way; (3) occurrence on weekdays and during the day; and (4) collisions at intersection and vehicle--vehicle sideswipes. The results show notable differences in risk factors by age group and confirm the need for preventive efforts that incorporate age-specific strategies.

Care and Management of the Child with Diabetes

The management and care of the child with diabetes is ever changing and increasingly complex. The past 20 years have seen a burst in technologic advances, diabetes research, and new information to facilitate optimal diabetes control. Application of those advances is necessary for home health care professionals involved in the care of children with diabetes and their families. Common issues of management for the child with diabetes need to be addressed, and practical information for home health care interventions needs to be developed for those who assist children with diabetes and their families. In light of managed care programs and limited hospital stays, home health care offers an opportunity to ensure appropriate and adequate diabetes education to care for the child with diabetes at home safely and effectively. Home health care professionals ideally should be a part of the diabetes management team but can also act as a bridge between the inpatient and outpatient settings.

Medical conditions, risk exposure, and truck drivers' accidents: an analysis with count data regression models

Recent studies do not agree on the possible relationship between medical conditions and traffic safety; most of them do not control for exposure factors. This problem has become more pertinent for scientific studies because of litigation that showed that present regulations about access to driver permits might contravene human rights legislation. In our study, we estimate the effect of different medical conditions on truck drivers' distributions of accidents. Our data and our models permit simultaneous control for age; medical conditions; exposure factors measured by hours, kilometer, and qualitative factors; and other characteristics of truck drivers. Our results show that diabetic truck drivers of the permit class for straight trucks have more accidents than drivers in good health. No other studied medical condition has a significant effect on individual accident distributions. Many risk exposure variables are also significant. The effect of age is discussed in detail.

Medical conditions and motor vehicle collision injuries in older adults

OBJECTIVE

To determine whether medical conditions that can impair sensory, cognitive, or motor function increase the risk of injury due to motor vehicle collision in older drivers.

DESIGN

Case-control study.

SETTING

Group Health Cooperative of Puget Sound, a large prepaid health plan.

PARTICIPANTS

Group Health members age 65 or older who were licensed drivers in 5 counties. Cases were injured while driving during 1987 or 1988. Controls were matched to cases on age, gender, and county of residence but experienced no such injury during the study years.

MEASUREMENTS

The outcome was injury requiring medical care due to a police-investigated motor vehicle collision. Risk factors evaluated included selected medical conditions active within the previous 3 years, as determined from the medical record.

MAIN RESULTS

Injury risk was 2.6-fold higher in older diabetic drivers (95% CI: 1.4-4.7), especially those treated with insulin (odds ratio [OR] = 5.8, 95% CI: 1.2-28.7) or oral hypoglycemic agents (OR = 3.1, 95% CI: 0.9-11.0), those with diabetes for over 5 years (OR = 3.9, 95% CI: 1.7-8.7), and those with both diabetes and coronary heart disease (OR = 8.0, 95% CI: 1.7-37.7). Increases were also found for older drivers with coronary artery disease (OR = 1.4), depression (OR = 1.7), alcohol abuse (OR = 2.1), or falls (OR = 1.4), but these associations could easily have arisen by chance.

CONCLUSIONS

Counseling about driving risks may be warranted for certain elderly diabetic drivers. Further research is needed to determine whether transient hypoglycemia or long-term complications explain these effects.

Diabetes and job performance: an empirical investigation

There are approximately 11 million people in the United States with diabetes, and the numbers are increasing by 6% annually. Still, the relationship between diabetes and job performance remains unclear and marked by bias. To help clarify this relationship, a multicriterion job-performance rating scale was developed to rate task behaviors, interpersonal behaviors, down-time behaviors, and hazardous behaviors. A volunteer sample of 53 subjects was selected from people with insulin-dependent diabetes mellitus (IDDM) and non-insulin-dependent diabetes mellitus (NIDDM). All subjects were rated individually by a supervisor, who also rated the norm for the work group. The norm rating was used to determine a norm-referenced control group. The subjects were rated better than the norm in all categories and on all criteria: composite job performance (P < .001), task behaviors (P < .01), interpersonal behaviors (P < .01), down-time behaviors (P < .05), and hazardous behaviors (P < .001).

The risks of licensing persons with diabetes to drive trucks

The 1990 Americans with Disabilities Act forbids employers to bar disabled persons from jobs unless employers can show the disabled person cannot perform the tasks. The Federal Highway Administration will not license persons with diabetes mellitus to drive commercial motor vehicles in interstate commerce. These individuals may experience severe hypoglycemia, greatly increasing their risk of losing control of the truck. This prohibition is currently being reexamined. We describe the disease process leading to severe hypoglycemia and its physical manifestations. To quantify the risks of licensing persons with diabetes to use insulin, we first estimate the number of potential insulin-using drivers. We estimate that 1420 insulin-using persons would seek licenses in the United States if they were permitted to do so (920 noninsulin dependent and 500 insulin dependent). Next, we estimate the annual incidence of mild and severe hypoglycemia in these populations. The third step is to estimate the number of hypoglycemic episodes while driving. Estimating the likelihood of a crash due to a mild or severe hypoglycemic episode is the fourth step. We estimate that an additional 42 crashes each year would occur if insulin using persons were licensed to drive commercial motor vehicles in interstate commerce (20 from insulin dependent and 22 from non-insulin dependent drivers).

Frequency and morbidity of severe hypoglycaemia in insulin-treated diabetic patients

To estimate the frequency and morbidity of insulin-induced hypoglycaemia, a retrospective survey was undertaken of the frequency of severe hypoglycaemia in 600 randomly selected patients with insulin-treated diabetes who were attending a large diabetic outpatient clinic in a teaching hospital. The resulting morbidity (hypoglycaemia-related injuries, convulsions, and road traffic accidents) was ascertained in 302 patients. One hundred and seventy-five (29.2%) of the 600 patients reported a total of 964 episodes of severe hypoglycaemia in the preceding year, giving an overall frequency for the group of 1.60 episodes patient-1year-1. The frequency of severe hypoglycaemia which was documented in 544 Type 1 (ketosis prone) diabetic patients was double that observed in a subgroup of 56 Type 2 diabetic patients who were being treated with insulin (1.70 vs 0.73 episodes patient-1year-1). In the subset of 302 patients, those who had experienced severe hypoglycaemia had greater morbidity associated with an estimated rate of injury of 0.04 injuries person-1year-1. Twenty (6.6%) patients reported a total of 37 convulsions associated with hypoglycaemia, 5 of which had occurred in the preceding year (0.02 convulsions person-1year-1). Five patients reported road traffic accidents in the preceding year which had been caused by hypoglycaemia. The only reliable predictors of severe hypoglycaemia were a history of previous severe hypoglycaemia (p < 0.001), a history of hypoglycaemia-related injury (p < 0.001) or convulsion (p < 0.001), and the duration of insulin therapy (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of epilepsy or diabetes mellitus on the risk of automobile accidents

BACKGROUND

Previous studies of possible associations between chronic medical conditions and traffic safety have been inconsistent and subject to bias because of the incomplete identification of affected persons. Recent advances in the diagnosis and management of epilepsy and diabetes mellitus have improved the control of these disorders and suggest a need to reexamine the risk of traffic mishaps among patients with these conditions.

METHODS

We conducted a population-based retrospective cohort study of 30,420 subjects 16 to 90 years of age, with and without epilepsy or diabetes mellitus. Subjects included all the licensed drivers in seven contiguous ZIP Code areas in which the Marshfield Clinic and St. Joseph's Hospital, Marshfield, Wisconsin, are the primary sources of medical care. Standardized rates of moving violations and accidents over a four-year period (1985 through 1988) were compared in affected and unaffected cohorts.

RESULTS

Standardized mishap ratios for subjects with diabetes were 1.14 for all moving violations (P = 0.23) and 1.32 for accidents (P = 0.01); for subjects with epilepsy the ratios were 1.13 for moving violations (P = 0.26) and 1.33 for accidents (P = 0.04).

CONCLUSIONS

We conclude that drivers with epilepsy or diabetes mellitus have slightly increased risks of traffic accidents as compared with unaffected persons. The increases in risk observed in our study were generally smaller than those in previous studies, and we believe they are not great enough to warrant further restrictions on driving privileges.

Motor vehicle driving among diabetics taking insulin and non-diabetics

OBJECTIVE

To determine whether rates of road traffic accidents were higher in diabetics treated with insulin than in non-diabetic subjects.

DESIGN

Controlled, five year retrospective survey.

SETTING

Diabetic, dermatology, and gastroenterology outpatient clinics.

PATIENTS

596 Diabetics treated with insulin (354 drivers) aged 18-65 attending two clinics and 476 non-diabetic outpatients (302 drivers).

MAIN OUTCOME MEASURES

Rates of accidents in diabetic and non-diabetic subjects.

RESULTS

A self completed questionnaire was used to record age, sex, driving state, and rates of accidents and convictions for motoring offences among diabetic and non-diabetic volunteers. For the diabetic volunteers further information was obtained on treatment, experience of hypoglycaemia, and declaration of disability to the Driving and Vehicle Licensing Centre and their insurance company. Accident rates were similar (81 (23%) diabetic and 76 (25%) non-diabetic drivers had had accidents in the previous five years). A total of 103 diabetic drivers had recognised hypoglycaemic symptoms while driving during the previous year. Only 12 reported that hypoglycaemia had ever caused an accident. Overall, 249 had declared their diabetes to an insurance company. Of these, 107 had been required to pay an increased premium, but there was no excess of accidents in this group.

CONCLUSIONS

Diabetic drivers treated with insulin and attending clinics have no more accidents than non-diabetic subjects and may be penalised unfairly by insurance companies.