Pulse pressure is associated with plasma amyloid-β transport dysfunction

Atherosclerosis is associated with plasma Aβ levels in non-hypertension patients

BACKGROUND

Growing evidence indicated that to develop of atherosclerosis observed more often by people with Alzheimer's disease (AD), but the underlying mechanism is not fully clarified. Considering that amyloid-β (Aβ) deposition in the brain is the key pathophysiology of AD and plasma Aβ is closely relate to Aβ deposition in the brain, in the present study, we investigated the relationships between atherosclerosis and plasma Aβ levels.

METHODS

This was a population based cross-sectional study. Patients with high risk of atherosclerosis from Qubao Village, Xi'an were underwent carotid ultrasound for assessment of atherosclerosis. Venous blood was collected on empty stomach in the morning and plasma Aβ1-40 and Aβ1-42 levels were measured using ELISA. Multivariate logistic regression analysis was performed to investigate the relationships between carotid atherosclerosis (CAS) and plasma Aβ levels.

RESULTS

Among 344 patients with high risk of atherosclerosis, 251(73.0%) had CAS. In the univariate analysis, the plasma Aβ levels had no significant differences between CAS group and non-CAS group (Aβ1-40: 53.07 ± 9.24 pg/ml vs. 51.67 ± 9.11pg/ml, p = 0.211; Aβ1-42: 40.10 ± 5.57 pg/ml vs. 40.70 pg/ml ± 6.37pg/ml, p = 0.285). Multivariate logistic analysis showed that plasma Aβ levels were not associated with CAS (Aβ1-40: OR = 1.019, 95%CI: 0.985-1.054, p = 0.270;Aβ1-42: OR = 1.028, 95%CI: 0.980-1.079, p = 0.256) in the total study population. After stratified by hypertension, CAS was associated with plasma Aβ1-40 positively (OR = 1.063, 95%CI: 1.007-1.122, p = 0.028) in the non-hypertension group, but not in hypertensive group. When the plasma Aβ concentrations were classified into four groups according to its quartile, the highest level of plasma Aβ1-40 group was associated with CAS significantly (OR = 4.465, 95%CI: 1.024-19.474, p = 0.046).

CONCLUSION

Among patients with high risk of atherosclerosis, CAS was associated with higher plasma Aβ1-40 level in non-hypertension group, but not in hypertension group. These indicated that atherosclerosis is associated with plasma Aβ level, but the relationship may be confounded by hypertension.

RAGE in circulating immune cells is fundamental for hippocampal inflammation and cognitive decline in a mouse model of latent chronic inflammation

BACKGROUND

Latent chronic inflammation has been proposed as a key mediator of multiple derangements in metabolic syndrome (MetS), which are increasingly becoming recognized as risk factors for age-related cognitive decline. However, the question remains whether latent chronic inflammation indeed induces brain inflammation and cognitive decline.

METHODS

A mouse model of latent chronic inflammation was constructed by a chronic subcutaneous infusion of low dose lipopolysaccharide (LPS) for four weeks. A receptor for advanced glycation end products (RAGE) knockout mouse, a chimeric myeloid cell specific RAGE-deficient mouse established by bone marrow transplantation and a human endogenous secretory RAGE (esRAGE) overexpressing adenovirus system were utilized to examine the role of RAGE in vivo. The cognitive function was examined by a Y-maze test, and the expression level of genes was determined by quantitative RT-PCR, western blot, immunohistochemical staining, or ELISA assays.

RESULTS

Latent chronic inflammation induced MetS features in C57BL/6J mice, which were associated with cognitive decline and brain inflammation characterized by microgliosis, monocyte infiltration and endothelial inflammation, without significant changes in circulating cytokines including TNF-α and IL-1β. These changes as well as cognitive impairment were rescued in RAGE knockout mice or chimeric mice lacking RAGE in bone marrow cells. P-selectin glycoprotein ligand-1 (PSGL-1), a critical adhesion molecule, was induced in circulating mononuclear cells in latent chronic inflammation in wild-type but not RAGE knockout mice. These inflammatory changes and cognitive decline induced in the wild-type mice were ameliorated by an adenoviral increase in circulating esRAGE. Meanwhile, chimeric RAGE knockout mice possessing RAGE in myeloid cells were still resistant to cognitive decline and brain inflammation.

CONCLUSIONS

These findings indicate that RAGE in inflammatory cells is necessary to mediate stimuli of latent chronic inflammation that cause brain inflammation and cognitive decline, potentially by orchestrating monocyte activation via regulation of PSGL-1 expression. Our results also suggest esRAGE-mediated inflammatory regulation as a potential therapeutic option for cognitive dysfunction in MetS with latent chronic inflammation.

Nonlinear relationship between pulse pressure and risk of cognitive impairment: A 4-year community-based cohort study in Xi'an, China

OBJECTIVES

It has been known that pulse pressure (PP) is a risk factor for cardiovascular disease and stroke, however, the relationship between PP and cognitive impairment is unclear.

METHODS

This was a community-based cohort study. Participates were followed-up for 4 years and new-onset cognitive impairment was diagnosed. Multivariable logistic regression and restricted cubic spline (RCS) were used to investigate the relationship between PP and cognitive impairment. Propensity score matching (PSM) and sensitivity analysis among ApoEε4 non-carriers were performed to confirm the results.

RESULTS

1462 participants were included at baseline and 1173 completed the follow-up. There were 42 (3.5%) new-onset cognitive impairment of whom 31 were diagnosed with MCI and 11 with dementia during the follow-up. Multivariable logistic regression analysis showed that PP was positively associated with cognitive impairment (OR = 2.853, 95% CI 1.079-7.548, p = 0.035), and RCS suggested a non-linear relationship (P_non-linear = 0.034). The risk of cognitive impairment merely changed when the PP was below about 46.7 mmHg and increased rapidly thereafter. After the covariates were well balanced using PSM (standardized mean differences <0.1 for all covariates), logistic regression analysis revealed the risk of cognitive impairment was still higher for those with high PP (OR = 3.369, 95% CI 1.202-9.441, p = 0.021). Sensitivity analysis showed consistent results with primary analysis.

CONCLUSION

PP is associated with cognitive impairment in a non-linear manner among middle-aged and elderly. The risk of cognitive impairment increases rapidly when PP exceeds about 46.7 mmHg, which may be informative for subsequent research of PP control ranges.

Pulse Pressure Is Associated with Rapid Cognitive Decline over 4 Years: A Population-Based Cohort Study

Aiming to investigate the relationship between pulse pressure (PP) and cognitive decline, cognitively normal subjects from a community-based longitudinal cohort were followed-up for 4 years. The Mini-Mental State Examination (MMSE) was used to evaluate global cognitive function, and a ≥2-point decrease in the MMSE score from baseline was defined as cognitive decline. Restricted cubic spline, multivariable linear regression and logistic regression were used to investigate the relationship between PP and cognitive decline. A total of 1173 participants completed the follow-up, and 205 (17.5%) met the criteria for cognitive decline. Restricted cubic splines showed no nonlinear relationship between PP and ΔMMSE (P_overall = 0.037, P_non-linear = 0.289) or cognitive decline (P_overall = 0.003, P_non-linear = 0.845). Multivariable linear regression analysis showed that PP was positively related to ΔMMSE (b = 0.021, p = 0.020). Multivariable logistic regression analysis showed that PP was positively associated with cognitive decline (OR = 1.020, p = 0.023). A stratified analysis found an association between PP and cognitive decline in participants who were aged ≤65 years, male, and APOEε4 noncarriers and who had school education ≤6 years or hypertension. A sensitivity analysis after propensity-score matching did not alter our findings. These findings highlight that elevated PP is associated with rapid cognitive decline, particularly in males, middle-aged, low-educated, hypertensive individuals and APOEε4 noncarriers.

Peripheral Transport Proteins Were Associated with 4-Year Cognitive Decline in APOE ɛ4 Non-Carriers: A Longitudinal, Population-Based Study

BACKGROUND

Soluble low-density lipoprotein receptor-related protein-1 (sLRP1) and soluble receptor of advanced glycation end products (sRAGE) play major roles in peripheral clearance of amyloid-β (Aβ).

OBJECTIVE

To determine the relationship between baseline sLRP1/sRAGE and early cognitive decline in a longitudinal study and explore the possible effect of apolipoprotein E (APOE) on their association.

METHODS

Cognitively normal subjects were followed-up for 4 years. The baseline plasma levels of sLRP1 and sRAGE were measured using commercial ELISA kits. Global cognition was evaluated by Mini-Mental State Examination (MMSE), and cognitive decline was defined as a ≥2-point decrease of MMSE after 4 years. The association between baseline sLRP1/sRAGE and 4-year cognitive decline were analyzed using logistic regression analysis. Interaction analysis was performed to discover the potential effect of APOE genotype on the relationship.

RESULTS

769 participants were included in the final analysis, with 122 subjects (15.86%) were cognitive decline. Baseline sLRP1/sRAGE levels were not associated with 4-year cognitive decline after multivariable adjustments in the total cohort. However, there was significant interaction effect between sRAGE and APOE genotype on cognitive decline (adjusted odds ratio [OR] = 2.09, 95% confidence interval [CI]: 1.13-3.86, p = 0.019). Lower levels of sRAGE were associated with increased risk of cognitive decline among APOE ɛ4 non-carriers (adjusted OR = 1.60, 95% CI: 1.04-2.48, p = 0.034).

CONCLUSION

Individuals with lower levels of sRAGE had an increased risk of 4-year cognitive decline in APOE ɛ4 non-carriers, indicating that the association between sRAGE and cognitive decline might depend on the APOE genotype. However, the specific mechanisms need to be further elucidated.

Blood Triglyceride and High-Density Lipoprotein Levels Are Associated with Plasma Amyloid-β Transport: A Population-Based Cross-Sectional Study

BACKGROUND

Studies have found that blood lipids are associated with plasma amyloid-β (Aβ) levels, but the underlying mechanism is still unclear. Two Aβ transporters, soluble form of low-density lipoprotein receptor related protein-1 (sLRP1) and soluble receptor of advanced glycation end products (sRAGE), are crucial in peripheral Aβ transport.

OBJECTIVE

The aim was to investigate the effects of lipids on the relationships between plasma Aβ and transporter levels.

METHODS

This study included 1,436 adults aged 40 to 88 years old. Blood Aβ, sLRP1, sRAGE, and lipid levels were measured. Univariate and multivariate analyses were used to analyze the relationships between lipids and plasma Aβ, sLRP1, and sRAGE.

RESULTS

After adjusting for all possible covariates, high-density lipoprotein (HDL-c) was positively associated with plasma Aβ42 and sRAGE (β= 6.158, p = 0.049; β= 121.156, p < 0.001, respectively), while triglyceride (TG) was negatively associated with plasma Aβ40, Aβ42, and sRAGE (β= -48.389, p = 0.017; β= -11.142, p = 0.020; β= -147.937, p = 0.003, respectively). Additionally, positive correlations were found between plasma Aβ and sRAGE in the normal TG (Aβ40: β= 0.034, p = 0.005; Aβ42: β= 0.010, p = 0.001) and HDL-c groups (Aβ40: β= 0.023, p = 0.033; Aβ42: β= 0.008, p = 0.002) but not in the high TG and low HDL-c groups.

CONCLUSION

Abnormal levels of TG and HDL-c are associated with decreased Aβ and sRAGE levels. Positive correlations between plasma Aβ and sRAGE were only found in the normal TG and HDL-c groups but not in the high TG and low HDL-c groups. These results indicated that dyslipidemia contributing to plasma Aβ levels might also be involved in peripheral Aβ clearance.

Relationship Between Amyloid-β Deposition and Blood-Brain Barrier Dysfunction in Alzheimer's Disease

Amyloid-β (Aβ) is the predominant pathologic protein in Alzheimer's disease (AD). The production and deposition of Aβ are important factors affecting AD progression and prognosis. The deposition of neurotoxic Aβ contributes to damage of the blood-brain barrier. However, the BBB is also crucial in maintaining the normal metabolism of Aβ, and dysfunction of the BBB aggravates Aβ deposition. This review characterizes Aβ deposition and BBB damage in AD, summarizes their interactions, and details their respective mechanisms.

Blood Pressure Level Is Associated With Changes in Plasma Aβ1 -40 and Aβ1-42 Levels: A Cross-sectional Study Conducted in the Suburbs of Xi'an, China

Objectives: Amyloid-β (Aβ) deposition in the brain is the hallmark of Alzheimer’s disease (AD) pathology. Hypertension is a risk factor for AD, but the effects of hypertension on Aβ deposition are not fully determined. Considering peripheral Aβ closely relates to Aβ deposition in the brain, we investigated the relationships between blood pressure (BP) level and plasma Aβ concentrations.

Methods: One-thousand and sixty-nine participants (age above 45) from a village in the suburbs of Xi’an, China were enrolled. Questionnaires and validated Chinese versions of the Mini-Mental State Examination (MMSE) were used to collect information about vascular risk factors and assess cognition function. The apolipoprotein E (ApoE) genotype was detected using PCR and sequencing. Plasma Aβ levels were measured using ELISA. The associations between BP and plasma Aβ levels were analyzed by using multivariate linear regression.

Results: Plasma Aβ_1–40 level was higher in high BP group than that in normal BP group (53.34 ± 8.50 pg/ml vs. 51.98 ± 8.96 pg/ml, P = 0.013), in high SBP group than that in normal SBP group (53.68 ± 8.69 pg/ml vs. 51.88 ± 8.80 pg/ml, P = 0.001) and in high MABP group than that in normal MABP group (54.05 ± 8.78 pg/ml vs. 52.04 ± 8.75 pg/ml, P = 0.001). After controlling for the confounding factors, SBP (b = 0.078, P < 0.001), DBP (b = 0.090, P = 0.008) and MABP (b = 0.104, P < 0.001) correlated with plasma Aβ_1–40 level positively in ApoE ε4 non-carriers, but not ApoE ε4 carriers.

Conclusions: Elevated BP levels were associated with increased plasma Aβ_1–40 levels in middle-aged and elderly ApoE ε4 non-carriers.

Associations between vascular risk factors and subsequent Alzheimer's disease in older adults

Background

The clinical guidelines related to the primary prevention of Alzheimer’s disease (AD) have focused on the management of vascular risk factors. However, the link between vascular risk factors and AD in older adults remains unclear. This study aimed to determine the association between vascular risk factors and subsequent AD in 178,586 older adults (age ≥ 65 years).

Methods

Participants were recruited from 2009 through 2010 and followed up for 6 years. We assessed various vascular risk factors (total cholesterol [TC], low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], triglycerides [TG], fasting glucose [FG], systolic blood pressure [SBP], diastolic blood pressure [DBP], pulse pressure [PP], and body mass index [BMI]) and their association with AD incidence, categorizing each vascular factor using current clinical guidelines.

Results

AD was observed in 6.0% of participants at follow-up. All lipid profiles (TC, LDL-C, HDL-C and TG) were positively associated with the risk of AD. SBP and PP were in negative associations with AD, and DBP was positively associated with AD. BMI exhibited a negative association with AD incidence. We found no significant association between FG and AD risk. The sex difference was observed to have effects on vascular risk factors.

Conclusions

In this study, we comprehensively investigated the association between eight vascular risk factors and the risk of incident AD. Our findings suggest that multiple vascular risk factors are related to the development of AD in older adults. These results can help inform future guidelines for reducing AD risk.

Non-linear Relationship Between Plasma Amyloid-β 40 Level and Cognitive Decline in a Cognitively Normal Population

Objectives

Recent studies regarding the relationships between plasma amyloid-β (Aβ) levels and cognitive performance had inconsistent results. In this study, we aimed to characterize the relationship between cognitive decline and plasma Aβ levels in a large-sample cognitively normal population.

Methods

This population-based, prospective cohort study included 1,240 participants with normal cognition. The Mini-Mental State Examination (MMSE) was used to assess cognitive function at baseline and 2 years later. Restricted cubic splines, multivariate logistic regression, and multivariate linear regression models were used to evaluate the type of relationship between cognitive decline during the 2-year follow-up period and plasma Aβ levels (Aβ₄₀, Aβ₄₂, and Aβ_42/40).

Results

Participants with moderate Aβ₄₀ levels had the highest risk of cognitive decline during a 2-year follow-up relative to individuals with low Aβ₄₀ [odds ratio (OR): 0.60, 95% confidence interval (CI): 0.45–0.81, p < 0.001] or high Aβ₄₀ (OR: 0.65, 95% CI: 0.49–0.87, p = 0.004) levels. The association between Aβ₄₀ and cognitive decline did not depend on sex, education level, or APOE ε4 status. There was an interaction found between age (≤ 65 and > 65 years) and Aβ₄₀ (p for interaction = 0.021). In individuals older than 65 years, there was a positive linear relationship between plasma Aβ₄₀ and cognitive decline (OR: 1.02, 95% CI: 1.00–1.04, p = 0.027). For participants ≤ 65 years old, the lower Aβ₄₀ and higher Aβ₄₀ groups had a lower risk of cognitive decline than the medium Aβ₄₀ group (OR: 0.69, 95% CI: 0.50–0.94, p = 0.02; OR: 0.63, 95% CI: 0.45–0.86, p = 0.004). None of relationship between plasma Aβ₄₂, Aβ_42/40 and cognitive decline was found during a 2-year follow-up.

Conclusion

The relationship between plasma Aβ₄₀ and cognitive decline was not linear, but an inverted-U shape in a cognitively normal population. The underlying mechanism requires further investigation.

Apolipoprotein E ε4 Allele is Associated With Plasma Amyloid Beta and Amyloid Beta Transporter Levels: A Cross-sectional Study in a Rural Area of Xi'an, China

OBJECTIVE

The effects of the Apolipoprotein E (ApoE) genotype on peripheral amyloid beta (Aβ) and Aβ transporter levels are still unclear. Soluble low-density lipoprotein receptor-related protein-1 (sLRP1) and soluble receptor of advanced glycation end products (sRAGE) are the major transporter for Aβ, which can prevent plasma Aβ from flowing into brain. The aim of this study was to investigate the relationships between the ApoE genotype and plasma Aβ, sLRP1, sRAGE levels.

DESIGN

Cross-sectional study.

SETTING

The committee office of the village.

PARTICIPANTS

Residents lived in the village for more than 3 years, aged 40-85 years (n = 1,119, 63.5% women).

MEASUREMENTS

Plasma biomarkers include ApoE genotype, Aβ, sLRP1, sRAGE, fasting blood-glucose, and blood lipids. General information, medical history, living habits, and cognitive status (cognitive impairment or not) were also collected.

RESULTS

After controlling for all possible covariates, multiple linear regression analysis showed that the plasma level of Aβ₄₂ was higher and log-transformed sLRP1 was lower in ApoE ε4 carriers than that in noncarriers (β_Aβ42 = 1.214, 95% confidence interval: 0.105-2.316, p_Aβ42 = 0.031; β_sLRP1 = -0.075, 95% confidence interval: -0.129 to -0.021, p_sLRP1 = 0.006, respectively). Partial correlation analysis showed that plasma Aβ₄₀ was positively correlated with log-transformed sLRP1 and log-transformed sRAGE (r_sLRP1 = 0.116, p_sLRP1 <0.001; r_sRAGE = 0.078, p_sLRP1 = 0.009, respectively). Plasma Aβ₄₂ was positively correlated with log-transformed sRAGE (r = 0.072, p = 0.017).

CONCLUSION

ApoE ε4 carriers had higher plasma Aβ₄₂ levels and lower sLRP1 levels. These data indicated that the ApoE ε4 allele may also contribute to the pathogenesis of Alzheimer's disease through its effects on peripheral Aβ₄₂ and sLRP1 levels, but it needs to be further elucidated.

The relationship between blood lipids and plasma amyloid beta is depend on blood pressure: a population-based cross-sectional study

Background

It is believed that deposition of amyloid beta (Aβ) in the brain is the central pathological changes of Alzheimer’s disease (AD), which triggers a series of pathological processes. However, the relationship between dyslipidemia and AD is uncertain. Considering the peripheral Aβ levels are related to brain Aβ deposition, we explore the relationships between blood lipids and plasma Aβ.

Methods

Participants who lived in the selected village of Xi’an for more than 3 years were enrolled, aged 40–85 years (n = 1282, 37.9% male). Fasting blood lipid, plasma Aβ levels, basic information and living habits were measured. Multiple linear regressions were used.

Results

In total population, blood lipids were not associated with plasma Aβ. After stratified by blood pressure, serum total cholesterol (TC) and low-density lipoprotein (LDL-c) were positively associated with plasma Aβ₄₂ levels (β_TC = 0.666, P_TC = 0.024; β_LDL-c = 0.743, P_LDL-c = 0.011, respectively) in normal blood pressure. LDL-c was negatively associated with plasma Aβ₄₀ levels (β = − 0.986, P = 0.037) in high blood pressure.

Conclusion

Elevated plasma Aβ₄₂ levels are associated with higher TC and LDL-c in normal blood pressure. Elevated plasma Aβ₄₀ levels are associated with lower LDL-c in high blood pressure. This indicated that the relationships between blood lipids and plasma Aβ were confounded by blood pressure.

The Level of Plasma Amyloid-β40 Is Correlated with Peripheral Transport Proteins in Cognitively Normal Adults: A Population-Based Cross-Sectional Study

BACKGROUND

Transport proteins, soluble low-density lipoprotein receptor-related protein-1 (sLRP1), and soluble receptor of advanced glycation end products (sRAGE), play an important role in the clearance of plasma amyloid-β (Aβ). However, their relationship is not clear.

OBJECTIVE

The aim was to explore the relationship between plasma levels of sLRP1, sRAGE, and Aβ in a cross-sectional study.

METHODS

A total of 1,185 cognitively normal participants (age above 40) from a village in the suburbs of Xi'an, China were enrolled from October 8, 2014 to March 30, 2015. Plasma Aβ40, Aβ42, sLRP1, and sRAGE were tested using a commercial ELISA. Apolipoprotein E (APOE) genotyping was conducted using PCR and sequencing. The relationship between plasma levels of sLRP1, sRAGE, and Aβ was analyzed using Pearson's correlation analysis and multiple linear regression.

RESULTS

In the total population, Log sLRP1 and Log sRAGE were positively correlated with plasma Aβ40 (r= 0.103, p < 0.001; r= 0.064, p = 0.027, respectively), but neither were associated with plasma Aβ42. After multivariable adjustment in the regression model, Log sLRP1 and Log sRAGE were still positively related with plasma Aβ40 (β= 2.969, p < 0.001; β= 1.936, p = 0.017, respectively) but not Aβ42. Furthermore, the positive correlations between transport proteins and plasma Aβ40 remained significant only in APOEɛ4 non-carriers after Pearson's analysis and multiple regression analysis after stratification by gene status.

CONCLUSION

The concentrations of plasma sLRP1 and sRAGE had a significant impact on the level of plasma Aβ40 in cognitively normal adults, especially in APOEɛ4 non-carriers. However, the mechanism by which the transport proteins are involved in peripheral Aβ clearance and the relationship between transporters and amyloid burden in the brain needs further validation.

Elevation of Plasma Amyloid-β Level is More Significant in Early Stage of Cognitive Impairment: A Population-Based Cross-Sectional Study

BACKGROUND

Aggregation and deposition of amyloid-β (Aβ) in the brain is the main pathological change of Alzheimer's disease (AD). Decreased Aβ42 in the cerebrospinal fluid has been confirmed as a biomarker of AD; however, the relationship between plasma Aβ and cognitive impairment is currently unclear.

OBJECTIVE

The aim was to explore the relationship between plasma Aβ and cognitive impairment in a cross-sectional study.

METHODS

A total of 1,314 subjects (age above 40) from a village in the suburbs of Xi'an, China were enrolled between October 8, 2014 and March 30, 2015. A validated Chinese version of the Mini-Mental State Examination and neuropsychological battery were used to assess cognition. Levels of plasma Aβ42 and Aβ40 were tested using commercial enzyme-linked immunosorbent assay. Relationship of plasma Aβ and cognitive impairment was analyzed using logistic regression analysis.

RESULTS

Of the enrolled subjects, 1,180 (89.80%) had normal cognition, 85 (6.47%) had possible cognitive impairment and 49 (3.73%) had probable cognitive impairment. Logistic regression analysis showed that the Aβ42/Aβ40 ratio (OR = 4.042, 95% CI: 1.248-11.098, p = 0.012) and plasma Aβ42 (OR = 1.036, 95% CI: 1.003-1.071, p = 0.031) was higher in the possible cognitive impairment than that in the normal cognition group. Furthermore, the plasma Aβ42/Aβ40 ratio was higher in the possible cognitive impairment group than that in the probable cognitive impairment group (OR = 0.029, 95% CI: 0.002-0.450, p = 0.011).

CONCLUSIONS

Levels of plasma Aβ42 and Aβ42/Aβ40 ratio were elevated in patients with possible cognitive impairment, indicating that plasma Aβ42 and Aβ42/Aβ40 ratio increases may be more pronounced in early stage of cognitive impairment.