In older people, diabetes is a disabling disease due to the associated vascular complications, multiple comorbidities and the increased prevalence of geriatric syndromes. Because of the complexity of diabetes in old age a comprehensive assessment is important at initial diagnosis, with the aim of preventing loss of autonomy and preserving independence.

Clinical presentation

Around 50% of older people with diabetes are asymptomatic.1 When symptoms are present they are often nonspecific, patients may feel generally unwell, tired or lethargic. Symptoms may be atypical such as anorexia rather than the typical polyphagia. Classic osmotic symptoms are usually less prominent in older age because of an increased renal threshold for glucose, resulting in reduced polyuria, and impairment of thirst sensation, resulting in reduced polydipsia. Diabetes complications such as nonketotic hyperosmolar coma may be the presenting symptom or diabetes may be first diagnosed during an acute illness or routine screening.

Diagnosis

Diabetes should be diagnosed if fasting plasma glucose is ≥ 7 mmol/L or two hour postprandial glucose ≥ 11.1 mmol/L.²

Normal glycaemia is defined as fasting plasma glucose < 6.1 mmol/L or two hour postprandial glucose < 7.8 mmol/L. Therefore, there are two categories between normal glycaemia and diabetes:

• Impaired fasting glycaemia when plasma fasting glucose is ≥ 6.1 but < 7 mmol/L

• Impaired glucose tolerance when two hour postprandial glucose is ≥ 7.8 but < 11.1 mmol/L

Patients in these two categories are at high risk of developing diabetes and vascular complications.3 HbA_1c can be used as a diagnostic test with a cut-off ≥ 48 mmol/mol (6.5%) for a diagnosis of diabetes. The advantages of testing for HbA_1c are: convenience to patients, less day to day variability, and international standardisation. However, HbA1c has high specificity (98.7%) for diagnosing diabetes but low sensitivity (46.8%) which means that more than 50% of individuals with diabetes may be missed.⁴

Assessment

In addition to traditional micro- and macrovascular complications seen in younger people, older people with diabetes are at risk of developing atypical complications or geriatric syndromes such as cognitive dysfunction, depression, disability, falls, persistent pain and urinary incontinence. Therefore, older people with diabetes should have a comprehensive assessment on diagnosis, see table 1.

Management

Lifestyle modification and drug therapy

Adopting a healthy lifestyle, such as weight reduction in overweight patients, regular exercise and smoking cessation, is beneficial across all age groups.

However, special considerations should be undertaken when making decisions about drug therapy in older people with diabetes, see table 2.

Glycaemic targets

These should be individualised taking into consideration the patient’s overall health and life expectancy. Both hyperglycaemia, which causes dehydration, visual impairment, infections and lethargy, and hypoglycaemia, which causes confusion and falls, need to be avoided. It is important to remember that older people may tolerate higher levels of blood glucose before they develop osmotic symptoms because of a higher renal threshold for glucose with increasing age. On the other hand, they may appear to tolerate lower levels of blood glucose because of diminished autonomic symptoms of hypoglycaemia with increasing age. Targets are day to day or long term:

Day to day: A comfortable daily target of random blood glucose > 4 but < 15 mmol/L seems suitable to avoid development of symptoms as blood glucose outside this range is likely to be symptomatic and results in cognitive changes.⁵ Maintaining blood glucose in this ‘comfort zone’ especially in frail patients may ensure ‘comfort care’ avoiding extreme blood glucose levels to maintain mental function and general wellbeing.⁶

Long term: Long-term targets are based on HbA1c levels which should be around 53 mmol/mol (7%) for the fit elderly in the community with new onset diabetes, similar to that for younger patients.

However, for older people with established cardiovascular disease and long-standing diabetes a safer target around 58 mmol/mol (7.5%) is appropriate. In frail older people with multiple comorbidities a target around 64 mmol/mol (8%) is suitable. Targets could be even higher for more frail elderly patients especially those in nursing homes with a very short life expectancy where day to day glucose levels are more important than the long term HbA1c value to avoid symptoms and preserve quality of life.7

Special considerations in older people

Reducing hypoglycaemia: The increased risk of hypoglycaemia in older people with diabetes is not only related to tight glycaemic control but also to overall health and associated multiple comorbidities.⁸

Older patients are at an increased risk of hypoglycaemia even at a comparable level of glycaemic control to younger patients. The use of sulfonylureas, stroke, transient ischaemic attack, heart failure and depression have been shown to predict an increased risk for hypoglycaemia in older people.9 Recognising symptoms and risk factors for hypoglycaemia is important, see tables 3 and 4, above. ^10-13

Medications should be reviewed, and patients taking longer acting sulfonylureas switched to shorter acting agents. In insulin-treated patients the new class of long-acting insulin analogues may be a good option as they reduce the risk of hypoglycaemia.

Patients who have erratic eating patterns and unpredictable caloric intake could be managed with a regimen where short-acting insulin analogues are administered only after meals, thus preventing insulin-induced hypoglycaemia if a meal is missed or only partly consumed.

Dementia: Older people with diabetes have been found to be twice as likely to develop Alzheimer’s disease or vascular dementia as age-matched controls without diabetes.¹⁴

Persistent hyperglycaemia may play a part in increasing cerebrovascular disease by inducing inflammation, endothelial dysfunction, oxidative stress and insulin resistance. These cerebrovascular changes may explain the increased incidence of vascular dementia.¹⁵

Accelerated brain ageing due to insulin dysregulation, altered amyloid metabolism, protein glycation and direct cerebral glucose toxicity may explain the increased incidence of Alzheimer’s disease.¹⁶

Hypoglycaemia, on the other hand, is related to cognitive dysfunction in a mutual way. Cognitive dysfunction increases risk of hypoglycaemia17 and a history of severe hypoglycaemia increases risk of cognitive dysfunction,¹⁸ see figure 1.

Structural changes in the brain have been noted to be associated with diabetes. Cerebral atrophy and lacunar infarctions are reported more frequently in older people with diabetes and contribute to cognitive dysfunction. Hippocampal atrophy has also been observed and correlated with impairment in immediate memory. The hippocampus is susceptible to acute metabolic changes suggesting that it might be susceptible to diabetes-related metabolic complications such as hypoglycaemia.¹⁹

Although there is an association between hyperglycaemia and cognitive dysfunction, it has been shown that intensive glycaemic control is not able to prevent a decline in mental function.²⁰

In a community-based study of 1,398 older patients with diabetes, mean (SD) age 70 (7.4) years, adherence to diabetes self-care tasks (taking diabetes medication, performing regular exercise, following a recommended eating plan, undertaking blood glucose monitoring and foot inspection) decreased as cognitive impairment increased. Specific self-care tasks

of exercise and diet adherence were the most strongly associated with cognitive impairment.²¹

The findings of this study may alert clinicians to the importance of screening for cognitive dysfunction if noncompliance with self-care tasks is observed, see table 5.

Care home residents: Around one in four residents in care homes has diabetes. Comorbidity burden is high in this population especially with regard to continence, feeding, mobility and communication. In one study, patients had a mean of four

comorbidities (range 1-8) in addition to diabetes.²² Therefore, diabetes management in these settings should take into account patients’ frail condition and complex needs.

Quality of life should be maintained without subjecting residents to unnecessary therapeutic interventions. Tight glycaemic control including dietary restriction, frequent blood testing, insulin injections and polypharmacy may be a burden leading to additional complications. For example, dietary restriction may cause weight loss, frequent finger pricks and insulin injections may lead to agitation especially in cognitively impaired patients and polypharmacy may increase risk of falls.

Hydration should be maintained because of impaired thirst sensation particularly in patients with dementia to avoid risk of volume depletion and hyperglycaemic crises.

Individualised vs disease oriented models of care: The individualised care model covers a holistic approach to address the complex needs of the individual rather than focusing on a single disease. The health status of older people with diabetes is too heterogeneous to develop a single intervention strategy to fit all. Therefore, educational programmes should be adapted to patients’ abilities. Each individual should have their own care plan — taking into consideration their wishes and preferences, functional status and life expectancy — putting quality of life at the heart of therapeutic goals.

Conclusion

Older patients with diabetes are a heterogeneous group with varying health status. The management of diabetes in older people poses unique challenges. The increased prevalence of comorbidities associated with ageing combined with the increased prevalence of geriatric syndromes contributes to the complexity of managing diabetes in older people.

The diagnosis of diabetes in older people also presents challenges as symptoms may be less prominent or atypical in old age. When diabetes is first diagnosed older patients should have a comprehensive assessment to screen for microvascular complications, screen and treat cardiovascular risk factors and screen for geriatric syndromes. Clinicians should adopt an individualised rather than a disease-orientated approach to care focused on maintaining and improving quality of life.

Cognitive and physical dysfunction are common in older people with diabetes which may affect health outcomes and quality of life. Individual therapeutic targets should take into consideration functional status, life expectancy and patient preferences.