Diabetes mellitus is an increasingly common chronic disease in all societies, with a greater proportion of cases arising in the working age population. There are up to 2.3 million people with diabetes in the UK, and an estimated 750,000 who have the condition but don’t know. Many of these are likely to be in work.
There are two types of diabetes. Type 1 diabetes is an auto-immune disease of insulin secretion, often arising in childhood or young adulthood. Its onset is usually clear‑cut with polyuria, ketoacidosis and, ultimately, collapse in coma. Insulin by injection is life-saving and required to maintain life. Type 1 diabetes is the least common form of the condition, accounting for between 5% and 15% of cases.
Type 2 diabetes is a disease of increasing insulin resistance promoted by increasing weight and sedentary habits in middle life in predisposed individuals. Initially, the pancreas increases insulin secretion to compensate, but in time this compensatory activity starts to fail and blood glucose rises, crossing the threshold of normal to levels initially categorised as “impaired glucose tolerance” and then to diabetes. Even after diagnosis, and despite treatment, in Type 2 diabetes insulin secretion gradually declines and blood glucose continues to rise.1, 2 This raised blood glucose will, over many years, damage blood vessels and lead to the well-recognised complications of diabetes such as retinopathy, cardiovascular disease, neuropathy and kidney disease.
Patients with Type 2 diabetes have markedly increased risk of stroke and myocardial infarction3 related to raised blood pressure and abnormal lipids, both of which seem to be associated with abdominal obesity and insulin resistance, a state of affairs which is described as the “metabolic syndrome”. Individuals with the syndrome may not yet have Type 2 diabetes but are at risk of developing it in the future. Metabolic syndrome is common in people with Type 2 diabetes (occurring in more than 90% of cases).
Controlling the disease
To prevent the onset of long-term complications of diabetes, blood glucose needs to be maintained close to normal for many years. In addition, to prevent myocardial infarction and stroke, blood pressure and lipids must be tightly controlled, particularly in Type 2 diabetes1, 2.
In Type 2 diabetes, in order to maintain blood glucose close to the normal non-diabetic levels, increasing treatment is required to compensate for progression over time. Initial treatment usually focuses on diet and exercise to reduce weight and improve insulin sensitivity, allowing even impaired pancreatic insulin secretion to control blood glucose. Oral agents can be added to further improve insulin sensitivity, reduce glucose absorption or stimulate insulin secretion. With the progression of the insulin secretion deficit Type 2 diabetes, increasing amounts of treatment and combinations of treatment are required. Overall levels of glycated proteins, of which haemoglobin A1c (HbA1c) is the most useful marker, are used to assess glucose control. It is common practice to review a patient for HbA1c and blood pressure every three months and for cardiovascular risk factors every year. Ultimately, on average, around 10 years after diagnosis, insulin will be required to keep blood glucose well controlled, although a patient with Type 2 diabetes is much less likely to become as acutely insulin deficient as a Type 1 patient.
The drug treatments for diabetes can be divided into those where an error in dosing or meal time could lead to hypoglycaemia with symptoms of activation of the sympathetic nervous system, and those where hypoglycaemia is a low risk (see table 1).
A regimen of incremental oral agents, which adheres closely to current guidance but uses drugs with low risk of hypoglycaemia, is: Metformin (up to 850mg three times daily) + Glitazone (eg Pioglitazone 30mg) + Gliptin (Sitagliptin 100mg once daily) + Glinide (Nateglinide 120mg three times daily).
The American Diabetes Association and the European Association for the Study of Diabetes guidance4 on Type 2 diabetes suggests forced titration of drugs and the addition of agents to achieve and keep HbA1c below 7%. HbA1c is measured every three months and treatment added each time HbA1c is above the 7% level. It is appropriate to take this approach with the above sequential oral agent dosing regimen, particularly since the risk of accumulation of these agents and onset of hypoglycaemia is low. If one agent is not tolerated, another from the same class can be substituted, and if one class is not tolerated or contraindicated, that step can be skipped.
The role of the OH physician
Managers work in partnership with occupational physicians and require guidance on whether employees can remain in a particular job or whether they need to be redeployed. Some occupations have tightly defined fitness standards to allow work to be carried out safely. A sound opinion about these standards allows for a careful match between the employee’s abilities and health whilst observing statutory requirements. This is especially true for the fitness assessments required in military employment. Periodic medical assessments in the transportation industry may reveal occult diabetes before it has an impact on employee health and safety.
Diabetic employees need to be assessed for the likelihood of sudden incapacity. Examples include an episode of hypoglycaemia, sudden cardiovascular event or loss of vision. Risk assessments need to be done in safety critical environments. Where control measures cannot be put in place then work should be restricted.
Legal issues
The Driver and Vehicle Licensing Agency5 restricts diabetics on insulin from holding Group II licences and also recommends that they should not drive emergency (“blue light”) vehicles due to the risk of sudden incapacity from hypoglycaemia. Similar restrictions are applied to train drivers6 but not all pilots7 on insulin. This is because aircraft have advanced automatic safety systems and, usually, two pilots.
Disability legislation8 requires consideration to be given to reasonable adjustments being made to the workplace. It does not require that adjustments for the disabled employee are made at all costs. If the disabled employee could endanger him or herself or others in the workplace then it is in the best interests of all concerned for him/her not to be there. Some environments may allow for the provision of equipment to assist with low vision and impaired sensation. However, for a driver or a pilot good vision and normal sensation are important.
Diabetes is a long-term condition, a true chronic illness. A diabetic employee may meet the required fitness standard at induction or at diagnosis, but this may change as complications develop. For these reasons diabetic employees in hazardous work need to be monitored regularly by the occupational health department. If a diabetic’s own GP has not carried out the necessary blood tests then the OH appointment is an opportunity to ensure that the necessary monitoring and education take place.
The OH appointment may need to include all elements of relevant history, lifestyle assessment, risk profiling and physical examination. Decision support tools and risk profile software allied to patient education materials are important adjuncts to this.
Referral routes
All diabetics should be encouraged to register with appropriate primary care services. Not all will do this, citing work and travel patterns as obstacles. Indeed, for those in employment, OH may provide the main healthcare service. Close liaison between all practitioners caring for the diabetic employee is important, with the OH physician taking the role of facilitator.
For advice on medication and treatment, OH physicians can refer to GPs or specialists. Employees whose absence has a significant financial impact on a company may find that their employer will fund referrals to ensure a rapid return to work. A return to work in a particular role may be an inducement to help patients achieve monitoring targets.
The OH/GP joint role
HbA1c needs to be monitored every three months and titrated diabetes drugs administered. The avoidance of hypoglycaemia may mean that a clear step-wise treatment algorithm is worth agreeing between the GP and a specialised diabetes service, individualised to the patient’s circumstances, and monitored for adherence and safety by the relevant OH service.
A diabetic patient who is having regular OH reviews to evaluate continued fitness for work in, for example, a safety critical environment, will be asked to provide evidence of appropriate treatment. This will include a record of daily, or more frequent, blood glucose measurements. A list of all medication taken (which could be the repeat prescription print-out) and evidence of attendance at ophthalmic and podiatric testing are useful. It is helpful to have copies of relevant blood results, especially HbA1c, lipids and renal function (estimated glomerular filtration rate).
Review appointments can be used to record weight, body mass index, waist circumference, blood pressure and urinalysis. This can be used in conjunction with blood results to show whether trends are going in the right direction or not.
There are strong associations between diabetes, hypertension, obesity and obstructive sleep apnoea syndrome9,10. It may be useful to ask diabetic patients specifically about quality of sleep and daytime sleepiness. It is helpful to have witness accounts about sleeping habits when considering the possibility of sleep apnoea as a diagnosis.
Health promotion messages are important. Those who take regular exercise, adopt a healthy diet and lose weight will do better than those who do not. Exercise on prescription is available in some areas. Strong encouragement should be given to smoking cessation. Greatest success is seen in those who join a “Stop smoking” group and have nicotine replacement therapy.
High alcohol consumption has an adverse effect on lipid function, liver function and blood pressure. It also affects glycaemic control. Diabetic patients should be encouraged to minimise alcohol intake. The concept of a unit of alcohol is not well understood most people think of it as a glass of wine or half a pint of beer. One unit of alcohol is 10ml of absolute alcohol 1 litre of 10% alcohol contains 10 units of alcohol. A 250ml glass of 12% alcohol wine has three units of alcohol.
Since cardiovascular risk is so much higher in diabetics than the equivalent non-diabetic population, it is important to encourage the employee to adopt healthy behaviours in terms of diet and to reinforce the need for aggressive cardiovascular risk reduction, to prevent disability related to cardiovascular disease during their working life and beyond. It should be the norm that diabetic employees are treated with aspirin and statins because of the strong evidence base that these interventions are effective in similar populations studied in cardiovascular outcome trials.
Diabetes affects many aspects of working life and a cooperative approach to managing the condition will promote safe working practices.
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Key points
Diabetes is increasing in the working population.
Diabetes is a chronic condition and complications may appear over time.
There are two types of diabetes – Type 1 and Type 2. The causes of these are different and they need managing in different ways.
Diabetic employees should be assessed for the likelihood of sudden incapacity and a risk assessment carried out in situations where safety may be compromised.
There are 2.3 million people with diabetes in the UK, the majority of whom have Type 2 diabetes. Many of these are in work.
There are employment limitations on diabetic employees – for example, insulin-dependent diabetics cannot normally drive trains or hold a Group II driving licence.
