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World J Diabetes. Apr 15, 2022; 13(4): 319-337
Published online Apr 15, 2022. doi: 10.4239/wjd.v13.i4.319
Table 1 Type 2 diabetes mellitus and its complications
Major complications of diabetes
Macrovascular (large artery damage)
Ischaemic heart disease
Cerebrovascular disease
Microvascular (peripheral neuropathy and damage to the small vessels)
Retinopathy: Retinal microaneurysm and retinal detachment
Nephropathy: Altered of renal function with microalbuminuria, proteinuria, and progression to chronic renal failure
Neuropathy
Table 2 Difference between vascular dementia, Alzheimer dementia, and mixed dementia

Characteristics
Vascular dementiaCerebral vascular network involving veins, arteries, capillaries.Clinical presentation is more variable
Alzheimer dementiaCaused by the death of nerve cells (neurons) in certain selected areas of the brain. Characteristic abnormalities (neuritic plaques and neurofibrillary tangles)
Memory impairment at initial clinical presentation.
Mixed dementiaVascular disease + Alzheimer's disease
Table 3 Summary of studies relating diabetes and Alzheimer's disease
Ref.
Study
n
Conclusion
Ott et al[33], 1999Prospective population-based cohort6370 older adultsDiabetes mellitus almost doubled the risk of dementia. Patients treated with insulin were at highest risk of dementia
Luchsinger et al[34], 2005Longitudinal1138 older adultsFour risk factors (diabetes, hypertension, heart disease, and current smoking) were associated with a higher risk of AD. The risk of AD increased with the number of vascular risk factors. Diabetes and current smoking were the strongest risk factors
Xu et al[38], 2009Population-based cohort study1248 dementia-free cohortUncontrolled diabetes increases the risk of Alzheimer's disease and VD. Their findings suggest a direct link between glucose dysregulation and neurodegeneration
Wang et al[36], 2012Population-based cohort study615529 diabetic patients; 614871 random controlsDiabetes may increase the risk of AD in both sexes and all ages
Tolppanen et al[40], 2013Case-Control study3012 diabetic patients; 3372 ADIndividuals with clinically verified AD are more likely to have a history of clinically verified and medically treated diabetes than the general aged population, although the difference is small
Huang et al[37], 2014Population-based cohort study1000000 random controls; 71433 diabetic patientsNewly diagnosed DM was associated with an increased risk of AD. The use of hypoglycemic agents did not ameliorate the risk
Gudala et al[35], 2013Meta-analysis28 studiesThe results showed a 73% increased risk of all type of demetia, 56% increase of AD, and 127% increase of VD in diabetes patients
Biessels et al[19], 2006Meta-analysis14 studiesThere is convincing evidence that shows an increased risk of dementia in people with diabetes. The risk factors and mechanisms that drive the association between diabetes and accelerated cognitive decline and dementia need to be identified before adequate treatment measures can be developed
Cheng et al[41], 2012Meta-analysis19 studiesDiabetes was a risk factor for incident dementia (including AD, VD, and any dementia) and MCI
Zhang et al[42], 2017Meta-analysis17 studiesThe risk of AD is higher among people with diabetes than in the general population