Table 2 Studies of hypertension and cognitive function in type 2 diabetes

Chen et al. [11] (2012)

Patients with type 2 diabetes; China

Cross-sectional, observational

Mean 55 ± 7 years

Hypertension defined on the basis of systolic blood pressure and diastolic blood pressure

MCI identified on the basis of cognitive screening instrument

None

Higher prevalence of hypertension in group with MCI compared with group free of MCI. Negative correlation of presence with hypertension with cognitive scores. No findings for blood pressure as continuous measure.

Bruce et al. [14] (2008)

Patients with type 2 diabetes participating in the Fremantle Diabetes Study; Australia

8-year retrospective, observational

Mean 76 ± 5 years

Systolic blood pressure and diastolic blood pressure at baseline and 8 years earlier

Dementia and MCI identified from screening instruments/clinical interview

Age and duration of diabetes

Prospective analyses: higher diastolic blood pressure 8 years earlier associated with increased risk of AD (but not MCI or any dementia) at follow-up. No findings in cross-sectional analyses.

Bruce et al. [21] (2008)

Patients with type 2 diabetes participating in the Fremantle Diabetes Study; Australia

8-year retrospective, 2-year prospective, observational

Mean 75 ± 4 years

Systolic blood pressure and diastolic blood pressure measured 8 years prior to baseline cognitive assessment

Dementia and MCI identified from screening instruments/clinical interview at baseline and 2-year follow-up. ‘Cognitive decline’ defined as downward conversion between ‘normal’, MCI, and dementia.

None

No association

Cukierman-Yaffe et al. [13] (2009)

Patients with type 2 diabetes participating in ACCORD-MIND; North America

Cross-sectional analysis of trial on blood pressure, lipids, and glycemic control

Mean 63 ± 6 years

Hypertension defined as use of anti-hypertensive medication or self-report of hypertension

Digit Symbol Coding (primary outcome), MMSE, Rey Auditory Verbal Learning, and Stroop (secondary outcomes)

Age

Association of hypertension with poorer performance on Digit Symbol Coding. No findings for other cognitive tests.

Hassing et al. [19] (2004)

OCTO-Twin Study of people without diabetes/hypertension, diabetes or hypertension alone, or co-morbid diabetes/hypertension; Sweden

6-year prospective, observational

Mean 83 ± 2 years

Hypertension defined as use of anti-hypertensive medication or on the basis of systolic blood pressure and diastolic blood pressure from medical records

MMSE administered at baseline and at 2-year intervals, dementia diagnosis prevalent at baseline, and incident dementia diagnosis

Age, sex, education, smoking, angina, MI, CHF, stroke, and TIA

Co-morbid diabetes/hypertension associated with steeper decline on MMSE (compared with group free of both conditions).

Statistically non-significant trend for higher prevalence and incidence of dementia in co-morbid diabetes/hypertension group than in remaining groups.

Johnson et al. [22] (2012)

National cohort of veterans with diabetes; USA

2-year retrospective, observational study of hospital records

Mean 76 ± 6 years

ICD codes for hypertension at baseline (2 years before analysis of incident dementia)

ICD codes for incident dementia diagnosis

Age, ethnicity, geographic area, duration of diabetes, co-morbidity according to HCC scores, and medication use

8 % increased risk of developing dementia during follow-up in patients with co-morbid hypertension at baseline.

Decreased risk in patients on anti-hypertensive medication (effect size dependent on medication), except for increased risk in patients receiving α-adrenoceptor blockers.

Manschot et al. [20] (2006)

Patients with type 2 diabetes participating in the Utrecht Diabetic Encephalopathy Study; The Netherlands

Cross-sectional, observational

Mean 66 ± 6 years

Hypertension defined on the basis of systolic blood pressure and diastolic blood pressure or use of anti-hypertensive medication

Composite scores on five cognitive domains from 11 cognitive tests, estimate of pre-morbid ability, cortical atrophy, and white matter lesions

Age, sex, and estimated pre-morbid ability

Statistically non-significant trend for lower scores on all cognitive domains except memory in patients with hypertension. Higher blood pressure associated with higher scores on memory domain and with greater severity of white matter lesions.

Manschot et al. [25] (2007)

Patients with type 2 diabetes participating in the Utrecht Diabetic Encephalopathy Study; The Netherlands

Cross-sectional, observational

Mean 66 ± 6 years

Hypertension defined on the basis of systolic blood pressure and diastolic blood pressure or use of anti-hypertensive medication

Composite score from 11 cognitive tests, estimate of pre-morbid ability, cortical atrophy, and white matter lesions

Age, sex, and estimated pre-morbid ability

Statistically non-significant trend for lower cognitive function in patients with hypertension (reaches statistical significance in final model including age, estimated pre-morbid ability, lipid-lowering drugs, and history of any vascular event). Higher blood pressure associated with greater severity of white matter lesions.

Umegaki et al. [16] (2014)

Patients with type 2 diabetes; Japan

6-year prospective, observational

Mean 74 ± 5 years

Mean of systolic blood pressure and diastolic blood pressure measured at baseline and annual follow-ups

Composite score from MMSE, Digit Symbol Coding, Stroop, and word recall. Analyses of ‘decliners’ versus ‘non-decliners’ on bases of composite score and individual cognitive tests.

None

No association

Williamson et al. [17] (2014)

Patients with type 2 diabetes participating in ACCORD-MIND blood pressure arm, with systolic blood pressure goal of 120 versus 140 mmHg; North America

40-month trial on blood pressure, lipids, and glycemic control

Mean 62 ± 6 years

Successful manipulation of blood pressure (groups differed on blood pressure following intervention)

Total brain volume at baseline and 40 months, Digit Symbol Coding (primary outcome), MMSE, Rey Auditory Verbal Learning, and Stroop (secondary outcomes) at baseline and 20 and 40 months

Glycemia treatment arm, visit effect, clinical center, and history of cardiovascular disease

No difference in 20- or 40-month cognitive decline treatment and control groups. Greater reduction in total brain volume in intervention than in control group.