The relationship between cognitive dysfunction and type 2 diabetes has been explored in some detail. It has been determined that diabetes increases the risk of all types of dementia by approximately twofold (Cheng et al, 2012; Gudala et al, 2013), with the mechanisms implicated including persistent hyperglycaemia and repeated episodes of hypoglycaemia (Crane et al, 2013; Feinkohl et al, 2014). In the presence of cognitive difficulties, irrespective of the cause, a number of key problems may emerge in those attempting diabetes self-care, such as deficits in numeracy, diabetes knowledge, insulin adjustment skills, ability to learn to perform insulin injections, adherence to medications, frequency of self-care activities, keeping appointments, and frequency and accuracy of reporting blood glucose monitoring. The relationship with dementia risk is less clear in type 1 diabetes and it is not certain that the same neuropsychological deficits experienced in type 2 diabetes occur and how diabetes self-care is affected.
A recent study in Northern California by Lacy et al (2018), summarised in our Digest here, examined the association between long-term glucose control, measured by HbA1c, and dementia incidence in 3,433 patients with type 1 diabetes, aged approximately 56 years at baseline, who were followed for an average of 6 years. By the end of the follow-up period, 155 cases of dementia were observed. The risk of dementia appeared to be increased in those with greater exposure to higher HbA1c levels (64–74 mmol/mol [8.0–8.9%] and ≥75 mmol/mol [≥9.0%]) and lower in those with lower HbA1c levels (42–52 mmol/mol [6.0–6.9%] and 53–63 mmol/mol [7.0–7.9%]). The difference equates to a greater than twofold increased risk of dementia in those with poorer glycaemic control and a 60% reduced risk in those with better glycaemic control.
A previous study from the UK also suggested that adults with type 1 diabetes in late middle age and older may be at increased risk of dementia occurring at a younger age than their non-diabetic counterparts (Smolina et al, 2015). Taken together, the results of these studies suggest that diabetes teams need to start screening for cognitive impairment in older adults with type 1 diabetes, as well as screening those with type 2 diabetes (Sinclair et al, 2014). Screening may serve as a prompt to ensure that unnecessary glycaemic exposure is minimised to maintain high cognition in a safe and effective way through education, by agreeing sensible HbA1c targets, and by appropriate glucose-lowering therapy.
Older adults with type 1 diabetes and dementia are increasingly being recognised as posing special challenges to healthcare teams in hospital and in care home settings, as a lack of self-care ability in those with moderate-to-severe cognitive impairment may worsen their nutritional state, increase their risk of hypoglycaemia, and jeopardise their recovery and outcomes. It is of paramount importance to identify these patients’ special needs, but this may not always happen if care staff members are not tuned in to this important issue.
More research into older people with type 1 diabetes is needed. The results of the study by Lacy and colleagues, however, provide some reassurance that the recommended glycaemic targets for those with type 1 diabetes are appropriate to lessen the cognitive sting of diabetes.
Click the links below to access the latest Diabetes Digests related to older people:
- Glycaemic control influences dementia risk in type 1 diabetes
- Symptom burden greatest in undiagnosed diabetes
- Applying evidence to improve diabetes care for older people
- Glargine 300 units/mL reduces nocturnal hypoglycaemia in over 65s
References
Cheng G, Huang C, Deng H, Wang H (2012) Diabetes as a risk factor for dementia and mild cognitive impairment: a meta-analysis of longitudinal studies. Intern Med J 42: 484–91
Crane PK, Walker R, Hubbard RA et al (2013) Glucose levels and risk of dementia. N Engl J Med 369: 540–8
Feinkohl I, Aung PP, Keller M et al (2014) Severe hypoglycemia and cognitive decline in older people with type 2 diabetes: The Edinburgh Type 2 Diabetes Study. Diabetes Care 37: 507–15
Gudala K, Bansal D, Schifano F, Bhansali A (2013) Diabetes mellitus and risk of dementia: a meta-analysis of prospective observational studies. J Diabetes Investig 4: 640–50
Lacy ME, Gilsanz P, Karter AJ et al (2019) Long-term glycemic control and dementia risk in type 1 diabetes. Diabetes Care 41: 2339–45
Sinclair AJ, Hillson R, Bayer AJ; National Expert Working Group (2014) Diabetes and dementia in older people: a Best Clinical Practice Statement by a multidisciplinary National Expert Working Group. Diabet Med 31: 1024–31
Smolina K, Wotton CJ, Goldacre MJ (2015) Risk of dementia in patients hospitalised with type 1 diabetes and type 2 diabetes in England, 1998–2011: a retrospective national record linkage cohort study. Diabetologia 58: 942–50
Attempts to achieve remission, or at least a substantial improvement in glycaemic control, should be the initial focus at type 2 diabetes diagnosis.
9 May 2024