So, hypos under 2 are thought to kill brain cells and risk decline in cognitive function. This is putative risk, because you can't actually see whether it does by doing cognitive function tests and then forcing a hypo before doing another one to compare.
Brief research suggests it's all very putative, unproven.
Brief research:
·
Jacobsen et al "Long-Term Effect of Diabetes and its Treatment on Cognitive Function" 2007 (356) New England Journal of Medicine 1842 – found no correlation between episodes of severe hypoglycaemia and lasting effect on cognitive function;
·
Munsen et al "Impact of Diabetes and Its Treatment on Cognitive Function Among Adolescents Who Participated in the Diabetes Control and Complications Trial" 2008 Diabetes Care (31, 10) 1933 – found no association between frequency of hypoglycaemia and decline on any cognitive domain.
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Seaquist et al "A Report of a Workgroup of the American Diabetes Association and The Endocrine Society" 2015 Diabetes Care (36, 5) 1384 – considered more work was necessary to understand the significance of hypoglycaemic episodes on the long term cognitive ability of adults with type 1 diabetes.
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Ewan et al "Mini-Review: Impact of recurrent hypoglycaemia on cognitive and brain function" Physiology & Behaviour 100(3) 234 – recurrent hypoglycaemia appears to cause brain adaptations which may enhance cognitive performance and fuel supply when euglycemic.
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Puente et al "Recurrent Moderate Hypoglycaemia Ameliorates Brain Damage and Cognitive Dysfunction Induced by Severe Hypoglycaemia" 2010 Diabetes Journals (59,4) 1055 - changes brought about by recurrent moderate hypoglycaemia can be viewed, paradoxically, as providing a beneficial adaptive response in that there is mitigation against severe hypoglycaemia–induced brain damage and cognitive dysfunction.
http://europepmc.org/backend/ptpmcrender.fcgi?accid=PMC2701294&blobtype=pdf
3 May 2007 New England Journal of Medicine
356:
1842–
1852 Jacobsen et al "Long-Term Effect of Diabetes and Its Treatment on Cognitive Function" – study on whether episodes of severe hypoglycaemia has any lasting effect on cognitive function – found no correlation?
http://care.diabetesjournals.org/content/31/10/1933.full
Musen et al, "Impact of Diabetes and Its Treatment on Cognitive Function Among Adolescents Who Participated in the Diabetes Control and Complications Trial" 7 July 2008 Diabetes Care (31, 10) 1933
There were a total of 294 reported episodes of coma or seizure. Neither frequency of hypoglycemia nor previous treatment group was associated with decline on any cognitive domain. As in a previous analysis of the entire study cohort, higher A1C values were associated with declines in the psychomotor and mental efficiency domain (
P < 0.01); however, the previous finding of improved motor speed with lower A1C values was not replicated in this subgroup analysis.
http://care.diabetesjournals.org/content/36/5/1384.full
Hypoglycemia and Diabetes: A Report of a Workgroup of the American Diabetes Association and The Endocrine Society, Seaquist et al Diabetes care 15 April 2013 (36, 5) 1384
-Despite such reassuring findings, recent investigation with advanced imaging techniques has demonstrated that adults with type 1 diabetes appear to call upon a greater volume of the brain to perform a working memory task during hypoglycemia (
45). These findings suggest that adults with type 1 diabetes must recruit more regions to preserve cognitive function during hypoglycemia than adults without the disease. More work will be necessary to understand the significance of these observations on the long-term cognitive ability of adults with type 1 diabetes.
http://care.diabetesjournals.org/content/33/9/1945.full.pdf+html
Asvold et al "Cognitive Function in Type 1 Diabetic Adults with Early Exposure to Severe Hypoclycemia" Diabetes Care 2010 (33,9) 1945
The findings suggest that early (childhood) exposure to SH may have lasting and clinically relevant effects on cognition….Possibly the developing brain is particularly vulnerable to the effects of SH (2,3,5,6,11). Unlike
previous long-term studies, we specifically included diabetic subjects with exposure to SH in early childhood.
This could explain why our data suggest larger persistent cognitive decline than previously reported in the studies of early- onset diabetes or SH in childhood.
Mini-review: Impact of recurrent hypoglycemia on cognitive and brain function
Physiology & Behavior, Volume 100, Issue 3, Pages 234-238
Ewan C. McNay, Victoria E. Cotero
Overall, RH appears to cause brain adaptations which may enhance cognitive performance and fuel supply when euglycemic but which pose significant threats during future hypoglycemic episodes.
http://diabetes.diabetesjournals.org/content/59/4/1055.full
Puente et al "Recurrent Moderate Hypoclycemia Ameliorates Brain Damage and Cognitive Dysfunction Induced by Severe Hypoglycemia" 19 January 2010 Diabetes (59,4) 1055
Antecedent recurrent moderate hypoglycemia preconditioned the brain and markedly limited both the extent of severe hypoglycemia–induced neuronal damage and associated cognitive impairment. In conclusion, changes brought about by recurrent moderate hypoglycemia can be viewed, paradoxically, as providing a beneficial adaptive response in that there is mitigation against severe hypoglycemia–induced brain damage and cognitive dysfunction.
http://archinte.jamanetwork.com/article.aspx?articleid=1696172
Yaffe et al "Association Between Hypoglycemia and Dementia in a Biracial Cohort of Older Adults With Diabetes Mellitus".
JAMA Intern Med. 2013;173(14):1300-1306.
Among older adults with DM, there seems to be a bidirectional association between hypoglycemia and dementia.
http://link.springer.com/article/10.1007/s00125-010-1983-6#page-2
Frier "Cognitive functioning in type 1 diabetes: the DCCT revisited" February 2011 Dibabetologia (54, 2) 233
This has revealed associations between mild impairment of psychomotor efficiency and hypertension, glycaemic control and the presence of retinopathy and nephropathy, while smoking history was associated with modest abnormalities in several cognitive domains. Neither macrovascular risk factors nor a history of severe hypoglycaemia was associated with the cognitive decrements; cerebral microangiopathy has been proposed as a possible underlying cause.