Dear editor
We read the article “Orthostatic blood pressure in people with mild cognitive impairment predicts conversion to dementia” by Hayakawa et alCitation1 with interest. It is well-known that many individuals with mild cognitive impairment (MCI) progress to dementia.Citation2 However, we do not exactly know which risk factors increase this risk and to what extent. Hypertension is a risk factor for Alzheimer’s disease and vascular dementia. However, the findings of this study make us consider hypotension as a new risk factor for dementia. Furthermore, a recently published 6-year prospective general population cohort study suggested that not only orthostatic hypotension (OH), but also symptoms of OH seemed to be risk factors for cognitive decline.Citation3 Notably, in the study by Elmstahl et alCitation3, hypertension and diabetes mellitus (DM) were more common in subjects with dementia. We would like to make some comments on this well-designed study.
The prevalence of DM is rather high in elderly individuals, and diabetic autonomic neuropathy may cause significant autonomic dysfunction. Furthermore, reactive hypoglycemic attacks and glucose variability may also increase the risk of Alzheimer’s disease in subjects with DM.Citation4–Citation6 Glucose variability and hypoglycemic attacks precipitated by insulin resistance may also affect conversion of MCI to dementia.Citation7 Accurate diagnosis of DM is especially important in older adults who may not experience typical symptoms of hyperglycemia and may even have normal fasting blood glucose levels. Thus, the diagnosis of DM may be easily overlooked in elderly subjects.Citation8 However, in the study by Hayakawa et alCitation1, a detailed assessment for the presence or absence of DM is not reported and the rate of DM in the study population seems to be lower than anticipated. We suggest that for an accurate diagnosis of DM, checking fasting glucose, postprandial glucose, and HbA1c levels is essential.Citation8 In conclusion, undiagnosed DM, glucose variability, and postprandial hypoglycemia might have contributed significantly to OH and to conversion of MCI to dementia in this study.
Disclosure
The authors report no conflicts of interest in this communication.
References
- HayakawaTMcGarrigleCACoenRFOrthostatic blood pressure behavior in people with mild cognitive impairment predicts conversion to dementiaJ Am Geriatr Soc20156391868187326313614
- Arevalo-RodriguezISmailagicNRoqueIFMMini-Mental State Examination (MMSE) for the detection of Alzheimer’s disease and other dementias in people with mild cognitive impairment (MCI)Cochrane Database Syst Rev20153CD01078325740785
- ElmstahlSWiderstromEOrthostatic intolerance predicts mild cognitive impairment: incidence of mild cognitive impairment and dementia from the Swedish general population cohort Good Aging in SkåneClin Interv Aging201491993200225429211
- WilletteAABendlinBBStarksEJAssociation of insulin resistance with cerebral glucose uptake in late middle-aged adults at risk for Alzheimer diseaseJAMA Neurol20157291013102026214150
- YaffeKFalveyCMHamiltonNAssociation between hypoglycemia and dementia in a biracial cohort of older adults with diabetes mellitusJAMA Intern Med2013173141300130623753199
- KimCSohnJHJangMUAssociation between visit-to-visit glucose variability and cognitive function in aged type 2 diabetic patients: a cross-sectional studyPLoS One2015107e013211826132234
- ZhongYZhangXYMiaoYThe relationship between glucose excursion and cognitive function in aged type 2 diabetes patientsBiomed Environ Sci20122511722424620
- KirkmanMSBriscoeVJClarkNDiabetes in older adultsDiabetes Care201235122650266423100048