Study | Sample | Design | Number | Baseline mean age | Lipids | Cognitive measures | Adjustment variables | Association with cognitive function |
---|---|---|---|---|---|---|---|---|
Bruce et al. [14] (2008) | Patients with type 2 diabetes participating in the Fremantle Diabetes Study; Australia | 8-year retrospective, observational | 302 | Mean 76 ± 5 years | Total cholesterol and HDL at baseline and 8 years earlier | Dementia and MCI identified from screening instruments/clinical interview | Waist-hip ratio | No associations in unadjusted cross-sectional or prospective analyses. Higher total cholesterol 8 years earlier protective of cognitive impairment short of dementia (but not dementia or all cognitive impairment) at baseline (finding independent of waist-hip ratio) |
Chen et al. [9] (2011) | Patients with type 2 diabetes; China | Cross-sectional, observational | 101 | Mean 63 ± 8 years | Total cholesterol, LDL, and HDL | MCI identified on the basis of cognitive screening instrument | None | Higher triglycerides, total cholesterol, and LDL in MCI group compared with group free of MCI. Negative correlation of total cholesterol with scores on cognitive screening instrument in patients with MCI. No finding for HDL. |
Chen et al. [11] (2012) | Patients with type 2 diabetes; China | Cross-sectional, observational | 157 | Mean 55 ± 7 years | Triglycerides, total cholesterol, LDL, and HDL | MCI identified on the basis of cognitive screening instrument | 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 | 2,977 | Mean 63 ± 6 years | Hyperlipidemia defined as use of lipid-lowering medication or untreated LDL cholesterol | Digit Symbol Coding (primary outcome), MMSE, Rey Auditory Verbal Learning, and Stroop (secondary outcomes) | Age | Association of hyperlipidemia with better performance on Digit Symbol Coding. No findings for other cognitive tests. |
Perlmutter et al. [10] (1988) | Patients with type 2 diabetes; USA | Cross-sectional, observational | 246 | Range 55-74 years | Triglycerides and total cholesterol | Digit Symbol Coding, Digit Span, and simple reaction time | Plasma glucose, HbA1c, body mass index, and history of hypertension | Lower cognitive function in ‘high’ compared with ‘low’ triglyceride groups (fully adjusted analysis); association of cholesterol with triglyceride (unadjusted analysis). |
Umegaki et al. [16] (2014) | Patients with type 2 diabetes; Japan | Six-year prospective, observational | 79 | Mean 74 ± 5 years | Mean of HDL and LDL 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 the basis of composite score and individual cognitive tests. | Age, education, estimated glomerular filtration rate, renin-angiotensin system inhibitor use, paraventricular hyperintensities, and deep white matter hyperintensities | Lower mean 6-year HDL in ‘decliners’ compared with ‘non-decliners’ on composite score and Stroop (unadjusted analysis). No finding for LDL. Mean 6-year HDL significant predictor in model of risk of decline on composite score (fully adjusted analysis). |
Williamson et al. [17] (2014) | Patients with type 2 diabetes participating in ACCORD-MIND lipid arm, receiving simvastatin + fenofibrate or simvastatin + placebo; North America | 40-month trial on blood pressure, lipids, and glycemic control | 1,538 | Mean 62 ± 6 years | Successful manipulation of cholesterol levels (groups differed on cholesterol 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 or 40-month change in total brain volume between intervention and control groups of lipid trial |
Van Harten et al. [12] (2007) | Patients with type 2 diabetes; The Netherlands | Cross-sectional, observational | 92 | Mean 73 ± 6 years | Total cholesterol/HDL ratio | Cognitive screening instruments, composite scores of four cognitive domains derived from scores on battery of 10 cognitive tests | Duration of diabetes, HbA1c, insulin use, hypertension, and polyneuropathy | No association |
Yanagawa et al. [15] (2011) | Patients with diabetes receiving exercise program four times per week versus none; Japan | 12-week trial on physical exercise intervention | 16 | Mean 71 ± 4 years | HDL and LDL (no intervention effect on HDL and LDL) | MMSE, word recall, Digit Symbol Coding, Stroop, and Trail-Making Test | Age, education, and body mass index | No difference in cognitive function between treatment groups following intervention |