With the increasing ageing population, the epidemiology of diabetes is shifting towards old age with increasing prevalence of comorbidities. Geriatric syndromes; especially cognitive dysfunction is emerging as a third complication category in addition to the traditional macro and microvascular disease in older people with diabetes. This review article investigates the relationship between diabetes and dementia, the impact one condition has on the other and explores the best practical management plans to maximise the safety and benefits of diabetes treatments.
Diabetes and dementia: the link
Diabetes and dementia: the risk
Diabetes and dementia: the consequences
Diabetes and dementia: practical management
Diabetes and dementia: glycaemic targets
With the increasing ageing population and changes in lifestyle, the prevalence of diabetes is likely to increase —especially among older individuals aged ≥75 years.1 Old age is associated with multiple comorbidities which, in turn, increase the complexity of care for older people with diabetes (Box 1). Geriatric syndromes such as cognitive and physical dysfunctions are emerging as a third category of complications in addition to the traditional micro and macrovascular disease in older people with diabetes.2 (Figure 1) As a result diabetes is recognised as a risk factor for institutionalisation of older people increasing the risk of nursing home admission by three fold.3 Unlike other chronic conditions, diabetes care is dependent upon the patient’s ability to perform self-care tasks, which may be compromised by the presence of geriatric syndromes; particularly cognitive dysfunction.
Persistent hyperglycaemia increases the risk of cerebrovascular disease by inducing inflammation, endothelial dysfunction, oxidative stress and insulin resistance leading to an increased incidence of vascular type dementia.4 On the other hand, accelerated brain ageing due to altered amyloid metabolism, increased protein glycosylation and direct cerebral glucotoxicity may explain the increased incidence of Alzheimer’s type dementia.5 Repeated episodes of hypoglycaemia, which is common in older people, may contribute to cognitive dysfunction and this relationship appears to be bidirectional. A history of severe hypoglycaemia increases the risk of cognitive dysfunction6 and similarly, cognitive dysfunction increase the risk of hypoglycaemia.7 Structural changes in the brain have been noted to be associated with diabetes and dementia. For example, cerebral and hippocampal atrophy are reported more frequently in older people with diabetes and contribute to cognitive dysfunction; particularly an impairment in immediate memory.8 It appears that insulin resistance within the brain shows a correlative increase in Alzheimer’s disease—suggesting that Alzheimer’s may be caused by a type of “brain diabetes”.
Progressive decline in cognitive function leading to dementia is a common occurrence in older people with diabetes. The risk of developing Alzheimer’s disease or vascular dementia is two fold in older people with diabetes compared to a cohort of age-matched control subjects without diabetes.9 In diabetics, it has been shown that the relative risk of developing Alzheimer’s disease is 1.56 (95% CI 1.41 to 1.73) or a 56% increase, vascular dementia is 2.27 (1.94 to 2.66) or a 127% increase and all types of dementia is 1.73 (1.65 to 1.82) or a 73% increase.10 Over 10 years, the risk of a diabetic developing dementia is 5.3% (95% CI 4.2 to 6.3) for the lowest score (-1) and 73.3% (64.8 to 81.8) for the highest (12-19) sum scores.
Age, microvascular disease, diabetic foot, cerebrovascular disease, cardiovascular disease, acute metabolic events, depression and education were most strongly predictive of dementia and constituted the risk score.11 In addition, the presence of diabetes accelerates the mortality rate in patients with dementia. In a retrospective Australian study, patients with combined dementia and diabetes died almost twice as fast as those without diabetes (hazard ratio 1.9, 95% CI 1.3 to 2.9).12
|BOX 1: Common geriatric syndromes
in older people with diabetes
|BOX 2: Screening for dementia|
This should be done as part of the patient’s annual review and prompt early dementia screening using the Mini Cog test if one of the following is observed:
Older people with diabetes and dementia experience difficulties in performing self-care tasks. 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 feet inspection) decreased as cognitive impairment increased. Specific self-care tasks of exercise and diet adherence were the most strongly associated with cognitive impairment.13 These individuals are also more likely to experience treatment-related complications such as severe hypoglycaemia—requiring assistance.14 Due to erratic eating patterns, associated with dementia, older people with diabetes are also at risk of malnutrition, dehydration and thus: worsening diabetic control (Figure 2). Carers of patients with diabetes and dementia will face extraordinary challenges to care for both conditions especially in those individuals who develop behaviour changes. Their needs should be identified early for greater support from the healthcare system.
Although there is an association between hyperglycaemia and cognitive dysfunction, it has been shown that tight glycaemic control is not able to prevent a decline in mental function.15 As discussed, once dementia develops —diabetes self-care deteriorates therefore, checking for cognitive dysfunction should be high priority on a clinician’s mind if a patient’s noncompliance with self-care tasks is observed (Box 2). Clinicians should also be aware that dementia may be associated with language impairment, disorientation and personality changes which may mimic the symptoms of hypoglycaemia.16 The Mini Cog test is a simple screening tool for dementia which has a sensitivity of 86.4% (95% CI 64.0 to 96.4%) and a specificity of 91.1% (85.6 to 94.6%) and takes only three minutes to perform; ideal for clinicians with limited consultation times.17 (Box 3)
|Box 3: The Mini-Cog Test: Mini-Cog scores 0–3 out of a maximum of 5 defines cognitive impairment|
Mini Cog test for dementia screening in older people with diabetes
Ask the person to repeat three items eg. lemon, key and balloon.
Provide a clock face:
1) Ask the person to draw the numbers of the clock face
2) Ask the person to draw the hands of the clock to show the time as ten to three.
Ask them to recall the three items.
|Score||One mark for each task, maximum 2 marks||One mark for each item recalled, maximum 3 marks|
As the decline in cognitive function continues, older people with diabetes and dementia will have complex needs due to increased dependency and unpredictable behavioural changes. For example, hydration should be maintained due to impaired thirst sensation to avoid risk of volume depletion and hyperglycaemic crises. In insulin treated patients the new class of long acting insulin analogues may be a good option as they reduce the risk of hypoglycaemia and can be conveniently injected once daily.18 Patients who have erratic eating patterns and unpredictable caloric intake could be managed with a regime where short-acting insulin analogues are administered only after meal consumption, thus preventing insulin induced hypoglycaemia if a meal is missed or only partly consumed.
Older people with dementia are likely to be frail with limited life expectancy and thus a target HbA1c of 64–75mmol/mol (8-9%) is appropriate. Tight glycaemic control in this population may be harmful by inducing hypoglycaemia and reducing quality of life. Also higher HbA1c >75mmol/mol (>9.0%) has been shown to be associated with increased mortality.19 More importantly, targets in this population should focus on short term day-to-day blood glucose levels rather than a long term HbA1c—due to a limited life expectancy. This will avoid both hyperglycaemia—which may lead to lethargy, dehydration, visual impairment and infections, and hypoglycaemia—which may lead to falls and confusion. Short-term targets in a comfortable daily range of random blood glucose >4 but <15mmol/L is appropriate as blood glucose outside this range is likely to be symptomatic and results in cognitive changes.20
Due to the ageing population, diabetes is increasingly becoming a disease of old age. As a result, diabetes in older people is associated with multiple comorbidities including increased prevalence of the geriatric syndromes such as cognitive and physical dysfunction. Therefore, although delivering care to this particular group of patients with complex needs is challenging, it is imperative to focus management on maximising the benefits and safety of diabetes treatment.
Bhavna Sharma, Department of Elderly Medicine, Rotherham General Hospital, Moorgate Road, Rotherham
Ahmed H Abdelhafiz, Department of Elderly Medicine, Rotherham General Hospital, Moorgate Road, Rotherham
Conflict of interest: none declared
7. Punthakee Z, Miller ME, Launer LJ, et al.; ACCORD Group of Investigators; ACCORD-MIND Investigators. Poor cognitive function and risk of severe hypoglycaemia in type 2 diabetes: post hoc epidemiologic analysis of the ACCORD trial. Diabetes Care 2012; 35: 787–93
13. Feil DG, Zhu CW, Sultzer DL. The relationship between cognitive impairment and diabetes self-management in a population-based community sample of older adults with Type 2 diabetes. J Behav Med 2012; 35: 190–99
15. Launer LJ, Miller ME, Williamson JD, et al.; ACCORD MIND investigators. Effects of intensive glucose lowering on brain structure and function in people with type 2 diabetes (ACCORD MIND): a randomised open-label substudy. Lancet Neurol 2011; 10: 969–77.
17. Sinclair AJ, Gadsby R, Hillson R, Forbes A, Bayer AJ. Brief report: Use of the Mini-Cog as a screening tool for cognitive impairment in diabetes in primary care. Diabetes Res Clin Pract 2013; 100: 23–25
18. Rosentock J, Daily G, Massi-Benedetti M, et al. Reduced Hypoglycaemia Risk With Insulin Glargine: A metaanalysis comparing insulin glargine with human NPH insulin in type 2 diabetes. Diabetes Care 2005; 28: 950-56