Patients with type 1 diabetes treated with insulin, with the potential for hypoglycaemia, must inform the National Driver Licence Service (NDLS) and adhere to precautions set out in the Medical Fitness to Drive Guidelines, April 2017.¹ The aim of this study was to assess awareness of and adherence to these guidelines, to see if certain groups of people have a higher compliance rate than others to the guidelines and to see if patients are receiving advice from their GPs regarding safe driving practices.

In Ireland driver health is overseen by both EU laws and regulations made in Ireland, under the Road Traffic Acts. The Medical Fitness to Drive Guidelines are an interpretation of these laws and have been made within the context of best medical evidence and best current international practice. They set out motor vehicle driving restrictions for many conditions including insulin-treated diabetes.

In Ireland, patients with type 1 diabetes account for 10-15% of the total population of people living with diabetes, which is just over 207,000. There is some controversy regarding whether patients with diabetes have higher accident rates compared to the general population.^2,3 The available studies fail to differentiate between types of diabetes and are dependent on patient recall. Hence good-quality, large, prospective studies are needed.

Previous studies have shown that professionals are often providing inadequate advice to patients with type one diabetes regarding safe driving.⁴ Although there has been data published in other countries on this topic, no significant data has yet been published in Ireland. 

The main safety concern for people with type one diabetes, with respect to driving, is hypoglycaemia. Factors which lead to an increased driving risk are patients who regularly experience severe episodes of hypoglycaemia; patients who have had a previous hypoglycaemic episode while driving; and patients who fail to check blood glucose levels before driving.^{5, 6}

It appears that patients are frequently basing their decision on whether or not to drive on their detection of symptoms of hypoglycaemia.⁷ However, it has been demonstrated that estimates of blood glucose based on symptoms are neither accurate nor safe.^{8, 9, 10}

There are clear deficits in aspects of both patient and healthcare professionals’ knowledge with regard to the recommendations for safe driving for patients with type one diabetes. Greater availability of information about minimising the risks associated with driving and diabetes is  required if patients with insulin-treated diabetes are to become better informed about and understand driving regulations and recommendations.⁷

Methods

In total, 107 participants took part in our study; 55 males  and 52 females. Occupations of participants ranged from manual (6), professional (48) and skilled workers (20), to unemployed (25) and retired (8) individuals. The average length of time in which patients had been diagnosed with type one diabetes was 18.5 years. 

We conducted a cross-sectional, quantitative survey using a SurveyMonkey link to a self-designed questionnaire. Questionnaires were distributed via diabetes clinics in CUH, GP surgery and online diabetes support groups. 

Data were entered into Microsoft Excel and analysed using SPSS software. The chi squared test was used to generate P values for the strength of association between study variables. The study was approved by the Clinical Research Ethics Committee of the Cork Teaching Hospitals.

Results 

• In total, 107 patients were surveyed and of these, 36 were aware of the NDLS guidelines

• Of the 36 people who appeared to be aware of the guidelines, only 15 (41.7%) always check their blood glucose level before driving

• A total of 83 participants always carry their testing kit in their vehicle while driving; 21 of these participants were over 40 years compared to 62 under 40 

• A total of 29 (27.1%) participants were aware of the appropriate management of hypoglycaemia while driving

• Finally, only 17 (15.9%) patients reported that they had received advice about safe driving from their GP.

We can see from these results that few patients with type 1 diabetes appear to be aware of the driving licence guidelines for patients on insulin or know how to manage hypoglycaemia appropriately. Most say they have not received safe driving advice from their GP. However, a majority do carry their testing kit in the car. Patients need to be better informed on the driving guidelines and GPs have a major role in ensuring patients have the appropriate information.  

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Testing kit in vehicle

We showed a statistically significant association between patient age and whether or not they carried a blood glucose testing kit in their vehicle while driving; 83 participants always carry their testing kit in their vehicle while driving, 21 of these participants were over 40 years compared to  62 under 40. (p = 0.001).

No relationship between gender and hypoglycaemia while driving were found. The age of participants ranged from 18-71 years with a mean age of 38 years.

There was a statistically significant association between  occupation and hypoglycaemia while driving. Patients with type 1 diabetes in the professional and skilled workforce were more likely to experience hypoglycaemia during driving compared to manual, retired and unemployed patients with diabetes (p = 0.022).

There was a statistically significant association between years driving and knowledge of the licensing authority guidelines – 87% of the participants who appeared unaware of the NDLS had their licence for greater than five years (p = 0.013).

Severe hypoglycaemia while driving

With regard to severe hypoglycaemia while driving, which is defined as an episode in which the patient required the help of another individual, one participant experienced a severe hypoglycaemic episode while driving in the previous year and two participants experienced two episodes. One patient stated how an episode of hypoglycaemia while driving had previously resulted in an accident. 

If hypoglycaemia is suspected while driving, 11 (10.3%) participants would continue driving but with increased care, 67 (62.6%) would stop driving, remove keys from ignition, move to passenger seat, eat/drink a carbohydrate source and then resume driving and 29 (27.1%) stated that they would stop driving, remove keys from ignition, move to passenger seat, eat/drink a carbohydrate source and then rest for at least 45 minutes before driving again.

Knowledge of glucose levels

• 88.8% (95/107) of participants considered less than 5mmol/l an unsafe level to drive

• 8.4% (9/107) considered greater than 5mmol/l an unsafe blood glucose level at which to drive

• 2.8% (3/107) of participants did not know below which blood glucose level it is considered unsafe to drive.

There was a statistically significant association between age of the patient and whether they had received advice about safe driving with type 1 diabetes, (p = 0.042). 

Almost half of the participants, 50 (47%), indicated that they had received advice; 38 (76%) of these participants were less than 40 years, 12 (24%) were over 40 years.

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Discussion

In this study, most participants were aware that it is unsafe to drive at blood glucose levels of less than 5mmol/l. This is important for patients to be aware of, as cognitive dysfunction has been shown to occur when blood glucose falls below this level.¹¹ However, for the most part, the blood glucose testing habits of drivers with type one diabetes are not adequate and a large proportion of participants were not compliant with guidelines.

It is disconcerting that 8.4% of patients never carry their testing kit in their vehicle while driving and only 34.6% always test blood glucose before driving. Fourteen per cent never test blood glucose before driving and of the 36 people who appeared to be aware of the Licensing Authority guidelines, only 15 (41.7%) reported that they always check their blood glucose level before driving.

Of note, there are no requirements to monitor blood glucose regularly in order to obtain an ordinary driving licence. However, failure to measure blood glucose could have legal consequences as previous studies have suggested,⁵ so proper patient education by healthcare professionals is paramount.

Only 29 (27.1%) participants were aware of the appropriate management of hypoglycaemia while driving; reflecting a minority of patients in the study.

The study was limited to patients with type 1 diabetes for a number of reasons. From reading the literature surrounding diabetes and driving, patients with type one and type two diabetes are for the most part distinct groups. For example, patients with type two diabetes are usually older and frequently have multiple comorbid conditions or serious sequelae of diabetes such as retinopathy or neuropathy which also play a role in safe driving.¹²

However, a future study could include patients with type two diabetes on insulin therapy or oral therapies which have the potential for hypoglycaemia and would undoubtedly yield interesting results.

Strengths and limitations

A strength of the study is that the sample size is comparable to, or in fact larger than, other similar studies in the field, most of which were published outside of Ireland, with the exception of a clinical audit carried out in Sligo Regional Hospital in 2013.¹³ 

A limitation to the study is that participants were not asked if they had informed the NDLS about their diabetes and one would be intrigued as to compliance with statutory requirements. Data was self-reported which may have introduced some bias. This study also includes responses from patients who are actively involved in support groups for patients with diabetes. One could infer that these patients are possibly more knowledgeable about driving regulations for patients with diabetes, compared type one diabetes patients in the general population.

Conclusion

Hypoglycaemia is a very real risk for patients with type 1 diabetes. It is important for us as health professionals to carefully examine current practices surrounding driving and to optimise opportunities to provide information/to reinforce precautions for driving to patients, as set out in the Medical Fitness to Drive Guidelines.

The clinical significance of this study is not only to  improve patient care with adequate education but also to help increase the safety of all drivers on our roads.

GPs often see diabetes patients more frequently than other health professionals involved in this area of care. They need to be well informed on current driving guidelines and regulations for patients with type 1 diabetes so that they can provide the most accurate, up-to-date information. 

References

1. Sláinte agus Tiomáint Medical Fitness to Drive Guidelines April 2017. Guiding Assessment for Licensing Drivers in Ireland. www.rsa.ie
2. MacLeod K. Diabetes and driving: towards equitable, evidence-based decision-making. Diabetic Medicine 1999;16(4):282-90
3. Cox DJ, et al. Diabetes and driving mishaps frequency and correlations from a multinational survey. Diabetes Care 2003; 26(8): 2329-34
4. Choudhary P, Amiel SA. Hypoglycaemia: current management and controversies. Postgraduate Medical Journal 2011; 87(1026):298-306 
5. Graveling AJ, Warren RE, Frier BM. Hypoglycaemia and driving in people  with insulin-treated diabetes: adherence to recommendations for avoidance. Diabetic Medicine 2004; 21(9): 1014-9
6. Inkster B, Frier BM, Choudhary P, et al. Diabetes and Driving. Diabetes, Obesity & Metabolism 2013; 15(9): 775-83 
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8. Weinger K, Kinsley BT, Levy CJ, et al. The perception of safe driving ability during hypoglycemia in patients with type 1 diabetes mellitus. The American Journal of Medicine 1999; 107(3): 246-53
9. Cox DJ, Clarke WL, Gonder-Frederick L, et al. Accuracy of perceiving blood glucose in IDDM. Diabetes care 1985; 8(6): 529-36
10. Weinger K, Jacobson AM, Draelos MT, Finkelstein DM, Simonson DC. Blood glucose estimation and symptoms during hyperglycemia and hypoglycemia in patients with insulin-dependent diabetes mellitus. The American Journal of Medicine 1995; 98(1): 22-31 
11. Blackman JD, Towle VL, Lewis GF, Spire J-P, Polonsky KS. Hypoglycmic thresholds for cognitive dysfunction in humans. Diabetes 1990; 39(7): 828-35
12. Chiang JL, Kirkman MS, Laffel LM, Peters AL. Type 1 diabetes through the life span: a position statement of the American Diabetes Association. Diabetes care. 2014; 37(7): 2034-54
13. Toomey M, Hennigan K, Molloy S, Murray P, Ferguson A, Coleman C. Hypoglycaemia and driving – clinical audit on the patients’ experience. Conduceted by diabetes nurse specilaists, September 2013, Sligo Regional Hospital