In this analysis elderly patients ≥ 70 years were more likely to have suffered from any severity (but mostly asymptomatic) hypoglycemia within the last 12 months prior to inclusion than younger patients < 60 years at comparable glycemic control. This is important because it should result in increased awareness of physicians and patients towards this severe but sometimes even asymptomatic complication and in an adjustment of treatment to prevent further complications.
Hypoglycemia in the elderly
It is well known that elderly patients are at an increased risk for hypoglycemia and often limits their proper management. Risk factors for hypoglycemia are similar to those in the young but are highly prevalent in the elderly. These include multiple co-morbidities, polypharmacy (≥ 5 medications), chronic renal or hepatic impairment, poor nutrition, use of sulfonylurea or insulin, acute illness, hypoglycemic unawareness and diminished counter regulatory responses.
Although it has been reported that hypoglycemia is more frequent in the young, rates of symptomatic hypoglycemia appear to be reduced in the elderly. This has been attributed to repetitive hypoglycemia leading to blunted symptomatic and hormonal responses to subsequent episodes leading to impaired awareness of hypoglycemia, also called hypoglycemia associated autonomic failure (HAAF). These patients often experience glucose concentrations below 2.0 mmol/l without becoming symptomatic. Furthermore, a number of variables such as glycemic control, alcohol, exercise, and age affects and reduces symptomatic and hormonal responses to subsequent hypoglycemia[20–24]. Elderly patients also report different symptoms and responses to hypoglycemia with less autonomic and more prominent neuroglycopenic symptoms. In this group, hypoglycemia can be misdiagnosed as dementia or neurological events.
Pharmacotherapy and hypoglycemia
Polypharmacy is an important predictor of subsequent hypoglycemic events. This is exemplified in our study with a more frequent use of cardiovascular medical treatment (beta blockers and diuretics in particular). Both drugs not only add to polypharmacy but are considered to impair glucose control by reducing hypoglycemia awareness and countermeasures or to simply increase blood glucose levels directly[27, 28]. Antidiabetic treatment was also different in the elderly, who were more frequently treated with sulfonylureas and less frequently with metformin, thiazolidinediones and DPP-4 inhibitors, a treatment pattern which was even more pronounced in elderly who experienced hypoglycemia during the last 12 months. The occurrence of hypoglycemia as a result of antidiabetic treatment of the elderly casts a cloud over modern risk adopted medical therapies and foils its achievement. Not surprisingly the uni- and also multivariate analyses found an elevated risk of hypoglycemia in those being treated with sulfonylureas. Taken together polypharmacy and in particular therapies with a remarkable hypoglycemic potential, such as sulfonylureas, should be used with caution, especially in patients with co-morbid disease such as heart failure or CAD, who require medication that might increase this risk for hypoglycemia.
Variables associated with hypoglycemia in the elderly
Beyond the use of sulfonylureas, stroke / TIA, heart failure and clinically relevant depression were predicting an increased risk for hypoglycemia in a multivariate model. Interestingly also patients who perform blood glucose self-measurement had an increased risk of (asymptomatic) hypoglycemia. This may be regarded as a self-fulfilling prophecy but is important not only because asymptomatic biochemical hypoglycemia may result in neurological impairment but because severe hypoglycemia may be masked as being asymptomatic in the elderly. Indeed we found that the majority of hypoglycemic events in the elderly were either asymptomatic or symptomatic but without the need for help.
Although the association of hypoglycemia with depression has already been described[29, 30], it is a finding with major public health implications. In a study of 99 adult patients with long-standing type-1 diabetes it was shown that poor sleep quality was independently associated with a positive hospital anxiety and depression scale (HADS), a possible explanation could be the occurrence of nocturnal hypoglycemia. Undisputable and self-explaining is the fact that hypoglycemia is causing reductions in health related quality of life as a study in type-2 diabetes mellitus patients showed and depression is a major determinant of this. Further research is warranted to evaluate if these mechanisms are solely able to explain the findings or if other variables should be taken into account.
Blood glucose targets in the elderly
It is important to understand that especially the elderly gain benefit from an individualized approach, instead of undifferentiated efforts to lower blood glucose. The ADA generally considers an HbA1c < 8.0% as being sufficiently tight in elderly patients with multiple co-morbidities, functional disabilities and / or limited life expectancy. The DDG proposes a more individualized approach and considers strict HbA1c values to be not very useful. However, to give an orientation of how elderly patients should be treated in terms of their blood glucose and HbA1c targets, the 2010 DDG practice guidelines propose a decision making process based on the actual health situation of the patients and his/her functional status. Patients with a good functional status (no reduction of their autonomy, good self-management and training skills), and a low level of co-morbidity (so called ‘go-go’ patients) should aim for an HbA1c between 6.5-7.0% without hypoglycemia. Patients with a reduced functional status (reduced autonomy, self-management and training skills), and multi-morbidity (so called ‘slow-go’ patients) should aim for an HbA1c of 7.0-8.0% without hypoglycemia. Only patients with significant functional reductions or limited life-expectancy (so called ‘no-go’ patients) should not aim for any certain HbA1c level, rather than to avoid symptoms of diabetes and hyper- or hypoglycemia. In this group of patients the focus is to preserve of a maximal quality of life[31–33].
It is important to highlight that the database for sufficient evidence based decisions and an optimal treatment of the elderly diabetic patients is weak. More efforts are required to set up a solid database of this steadily increasing group of patients. The necessity to include more of the elderly into clinical trials on the treatment of diabetes and to perform functional and cognitive assessments accordingly is a challenging requirement of geriatric societies with a high prevalence of diabetes in order to optimize medical therapy.
Results in perspective
Just recently a new consensus statement on the treatment of type-2 diabetes in the elderly was developed by the International Association of Gerontology and Geriatrics (IAGG), the European Diabetes Working Party for Older People (EDWPOP), and the International Task Force of Experts in Diabetes. They stated that hypoglycemia is highly prevalent and underrecognized in older people and that longer-acting sulfonylureas (or insulin) confer an increased risk. In those at high risk sulfonylureas should be avoided and DPP-4 inhibitors or, in the case of a BMI > 35 kg/m2, GLP-1 analogues should be considered. In addition they recommend not to lower blood glucose too aggressively in the elderly. These recommendations are consistent with our own findings and the potential clinical implications of our work.
Despite the considerable strength of the study in documenting real world patients, treatment patterns, co-morbidity and treatment related events a few limitations of the present analysis deserve mentioning. 1) The present analysis only considered oral antidiabetic drugs for the evaluation of hypoglycemia in the elderly. Therefore it is consistent with prior data that we identified sulfonylurea but not insulin as being associated with events. 2) Hypoglycemic events were recorded on an anamnestic basis where physicians and patients were required to recall events within the last 12 months. The bias however appears to be reasonably confined because preliminary data for the first year of follow-up resulted in similar hypoglycemia rates. 3) While we also considered to look at the very elderly (80+) we chose a definition of 70+ as being elderly. This was because of the quantitative importance of this patient group which makes up almost one third of patients in clinical practice. 4) Clinical diagnoses on co-morbid disease conditions were not validated but relied on the physicians’ assessment instead. This is common practice in this type of registries and cannot be alleviated because of financial constraints and the acquisition of data in real world clinical practice and its well known constraints of time.