Research
Original Investigation
Associations Between Cerebral Small-Vessel Disease and Alzheimer Disease Pathology as Measured by Cerebrospinal Fluid Biomarkers Maartje I. Kester, MD, PhD; Jeroen D. C. Goos, MD, PhD; Charlotte E. Teunissen, PhD; Marije R. Benedictus, MSc; Femke H. Bouwman, MD, PhD; Mike P. Wattjes, MD, PhD; Frederik Barkhof, MD, PhD; Philip Scheltens, MD, PhD; Wiesje M. van der Flier, PhD
IMPORTANCE It remains unclear if and how associations between cerebral small-vessel
CME Quiz at jamanetworkcme.com
disease and Alzheimer disease (AD) pathology lead to cognitive decline and dementia. OBJECTIVE To determine associations between small-vessel disease and AD pathology. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study from January 2002 to December 2012 using the memory clinic–based Amsterdam Dementia Cohort. The study included 914 consecutive patients with available cerebrospinal fluid (CSF) and magnetic resonance imaging; 547 were patients diagnosed as having AD (54% female, mean [SD], 67 [8]; Mini-Mental State Examination score, mean [SD], 21 [5]), 30 were patients diagnosed as having vascular dementia (37% female, mean [SD], 76 [9]; Mini-Mental State Examination score, mean [SD], 24 [4]), and 337 were control participants with subjective memory complaints (42% female, mean [SD], 59 [59]; Mini-Mental State Examination score, mean [SD], 28 [2]). Linear regressions were performed with CSF biomarkers (log transformed) as dependent variables and magnetic resonance imaging measures (dichotomized) as independent, adjusted for sex, age, mediotemporal lobe atrophy, and diagnosis. An interaction term for diagnosis by magnetic resonance imaging measures was used for estimates per diagnostic group. MAIN OUTCOMES AND MEASURES We examined the associations of magnetic resonance imaging white matter hyperintensities (WMH), lacunes, microbleeds with CSF β-amyloid 42 (Aβ42), total tau, and tau phosphorylated at threonine 181 (P-tau181) as well as for a subset of apolipoprotein E (APOE) ε4 carriers and noncarriers. RESULTS Microbleed presence was associated with lower CSF Aβ42 in AD and vascular dementia (standardized beta = −0.09, P = .003; standardized beta = −0.30, P = .01), and higher CSF tau in controls (standardized beta = 0.10, P = .03). There were no effects for P-tau181. The presence of WMH was associated with lower Aβ42 in control participants and patients with vascular dementia (standardized beta = −0.18, P = .002; standardized beta = −0.32, P = .02) but not in patients with AD. There were no effects for tau or P-tau181. The presence of lacunes was associated with higher Aβ42 in vascular dementia (standardized beta = 0.17, P = .07) and lower tau in AD (standardized beta = −0.07, P = .05) but there were no effects for Aβ42 or P-tau181. Stratification for apolipoprotein E genotype revealed that these effects were mostly attributable to ε4 carriers. CONCLUSIONS AND RELEVANCE Deposition of amyloid appears aggravated in patients with cerebral small-vessel disease, especially in apolipoprotein E ε4 carriers, providing evidence for pathophysiological synergy between these 3 biological factors.
JAMA Neurol. 2014;71(7):855-862. doi:10.1001/jamaneurol.2014.754 Published online May 12, 2014.
Author Affiliations: Alzheimer Center, Department of Neurology, VU University Medical Center, Amsterdam, the Netherlands (Kester, Goos, Benedictus, Bouwman, Scheltens, van der Flier); Department of Clinical Chemistry, VU University Medical Center, Amsterdam, the Netherlands (Teunissen); Department of Radiology, VU University Medical Center, Amsterdam, the Netherlands (Wattjes, Barkhof); Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, the Netherlands (van der Flier). Corresponding Author: Maartje I. Kester, MD, PhD, Alzheimer Center, Department of Neurology, VU University Medical Center, PO Box 7057, 1007 MB Amsterdam, the Netherlands ([email protected]).
855
Copyright 2014 American Medical Association. All rights reserved.
Downloaded From: http://archneur.jamanetwork.com/ by a J H Quillen College User on 06/04/2015
Research Original Investigation
Small Vessel Disease and Alzheimer Pathology
A
lzheimer disease (AD) is thought to be caused by amyloid aggregation and the formation of tau tangles.1 By contrast, in vascular dementia (VaD), infarcts or profuse white matter disease are considered the cause of cognitive decline.2 However, postmortem studies show a high prevalence of mixed pathology, especially in elderly populations.3 Many studies show cerebral small-vessel disease (SVD) and vascular risk factors to increase the risk of developing AD,4,5 while in both VaD and SVD, signs of AD pathology have been reported.6-8 It remains unclear how the interaction between SVD and AD pathology leads to dementia. Small-vessel disease could be an independent process leading to dementia in combination with coexisting yet unrelated AD pathology, but ischemic SVD might also contribute directly to AD pathology, eg, by accelerating the rate of amyloid deposition owing to ischemic changes or by inducing ischemia owing to amyloid deposition in the vessels (cerebral amyloid angiopathy [CAA]).9-12 The apolipoprotein E (APOE) ε4 genotype is a well-known risk factor not only for AD but also for cardiovascular disease and CAA, and it could be a modifying factor in the association of SVD and AD.13-17 Cerebrospinal fluid (CSF) β-amyloid 42 (Aβ42), total tau (tau), and tau phosphorylated at threonine 181 (P-tau181) are considered to reflect AD pathophysiology.18 White matter hyperintensities (WMH) and lacunes are magnetic resonance imaging (MRI) measures for ischemic SVD.2 Microbleeds (MBs) are considered a marker of underlying CAA and have also been related to hypertensive vasculopathy.9,19 By examining relationships of MRI-based MBs, WMH, and lacunes with levels of CSF Aβ42, tau, and P-tau181 in patients with AD, patients with VaD, and control participants, we explored the relationship between SVD and AD pathology. In addition, we examined the modifying effects of the APOE genotype on these relations.
Methods Study Population We included 914 consecutive patients in our study; 547 were patients diagnosed as having AD, 30 were patients diagnosed as having VaD, and 337 were control participants with subjective memory complaints from the memory clinic–based Amsterdam Dementia Cohort with available data on their CSF and MRI. All patients underwent a standard dementia screening including physical and neurological examination as well as laboratory tests, electroencephalogram, and brain MRI. Cognitive screening included Mini-Mental State Examination (MMSE) and usually involved comprehensive neuropsychological testing. The diagnosis of probable AD was made according to the National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association criteria20 and all patients fulfilled core clinical criteria according to National Institute on Aging– Alzheimer’s Association.21 Diagnosis of VaD was made according to the National Institute of Neurological Disorders and Stroke–Association Internationale pour la Recherche et l'Enseignement en Neurosciences criteria.2 When results of all 856
examinations were normal, patients were considered to have subjective memory complaints. Patients with mild cognitive impairment 22 or with a psychiatric disorder were not included. Diagnoses were made by consensus of a multidisciplinary team, without knowledge of CSF results or APOE genotype. Patients were asked about education, current use of medication, alcohol use, smoking history, and medical history. Diabetes mellitus was defined as use of glucoselowering agents or known history of diabetes, hypertension as use of antihypertensive agents or known history of hypertension, hypercholesterolemia as known history of hypercholesterolemia, and myocardial infarction as known history of myocardial infarction. The local institutional review board at the VU University Medical Center approved the study and all patients provided written informed consent.
MRI Assessment Scans were obtained on 4 different MRI scanners (in order of frequency): Signa 3.0-T (n = 557) (GE), Magnetom Impact 1.0-T (n = 243) (Siemens), Sonata 1.5-T (n = 77) (Siemens), Signa 1.5-T (n = 20) (GE), and Avanto 1.5-T (n = 16) (Siemens). The MRI rater was a neuroradiologist with special dementia neuroimaging expertise and was blind to clinical data. Microbleeds were defined as rounded hypointense homogeneous foci up to 10 mm in the brain parenchyma on T2*-weighted images. On the fluidattenuated inversion recovery (FLAIR) sequence, WMH were assessed using the Fazekas scale (none, punctuate, early confluent, confluent; score 0-3).23 Lacunes were defined as deep lesions from 3 to 15 mm with CSF-like signal on FLAIR, T1weighted, and T2-weighted images. Medial temporal lobe atrophy (MTA) was rated (0-4) using oblique coronal reconstructions of T1-weighted gradient-echo volume sequences perpendicular to the long axis of the hippocampus.24 Global cortical atrophy was assessed on the axial FLAIR sequence (0-3).25 On both scales, maximal atrophy is represented by the highest score. Magnetic resonance imaging readings were dichotomized as the following: MBs, 0 vs 1 or more; WMH, 0 or 1 vs 2 or 3; lacunes, 0 vs 1 or more; and MTA, (average score left and right side) 0 or 1 vs 2 or more.
CSF Analysis Cerebrospinal fluid was obtained by lumbar puncture using a 25-gauge needle and was collected in 10-mL polypropylene tubes. Within 2 hours, CSF samples were centrifuged at 1800g for 10 minutes at 4°C. A small amount of CSF was used for routine analysis including total cells, total protein levels, and glucose levels. Cerebrospinal fluid supernatant was transferred to 0.5- or 1-mL polypropylene tubes and stored at −20°C for enzyme-linked immunosorbent assay analysis within 1 month. Biomarkers of CSF were measured with Innotest sandwich enzyme-linked immunosorbent assay as previously described.26 As the manufacturer does not supply controls, the performance of the assays was monitored with pools of surplus CSF specimens. The mean (SD) intra-assay coefficient of variation was 2.0% (0.5%) for Aβ42, 3.2% (1.3%) for tau, and 2.9% (0.8%) for P-tau181 as calculated from averaging the CV of duplicates from 5 runs randomly selected over 2 years. The mean (SD) interassay coefficient of variation was 10.9% (1.8%) for Aβ42,
JAMA Neurology July 2014 Volume 71, Number 7
Copyright 2014 American Medical Association. All rights reserved.
Downloaded From: http://archneur.jamanetwork.com/ by a J H Quillen College User on 06/04/2015
jamaneurology.com
Small Vessel Disease and Alzheimer Pathology
Original Investigation Research
Table 1. Baseline Characteristicsa Control Participants (n = 337)
Characteristic Female, No. (%) Age, mean (SD), y c
Patients With AD (n = 547)
Patients With VaD (n = 30)
143 (42)
293 (54)b
11 (37)
59 (9)
67 (8)b
67 (9)b b
APOE ε4 carrier, No. (%)
111 (34)
337 (67)
13 (48)
MMSE score, mean (SD)d
28 (2)
21 (5)b
24 (4)b,e
Aβ42
893 (232)
490 (176)b
638 (233)b,e
Tau
267 (175)
692 (404)b
312 (180)e
47 (22)
89 (40)b
42 (19)e
Microbleeds present
47 (14)
117 (21)b
Lacunes present
15 (5)
40 (7)
24 (80)b,e
WMH>1
27 (8)
124 (23)b
Global cortical atrophy>1
13 (4)
MTA>1
CSF biomarker levels, mean (SD), pg/mL
Abbreviations: Aβ42, β-amyloid 42; AD, Alzheimer disease; APOE, apolipoprotein E; CSF, cerebrospinal fluid; MCI, mild cognitive impairment; MMSE, Mini-Mental State Examination; MRI, magnetic resonance imaging; MTA, mediotemporal lobe atrophy; P-tau181, tau phosphorylated at threonine 181; VaD, vascular dementia; WMH, white matter hyperintensities. a
Differences between diagnosis categories were assessed using analysis of variance with post hoc Bonferroni corrections or Fisher exact test when applicable.
25 (83)b,e
b
P < .05 vs control participants.
150 (28)b
7 (23)b
c
13 (4)
296 (54)b
16 (53)b
Data for APOE genotype were available for 861 patients (327 control participants, 507 patients with AD, and 27 patients with VaD).
Hypertension
88 (26)
172 (31)
24 (80)b,e
d
Hypercholesterolemia
63 (19)
128 (23)
13 (43)b,e
Diabetes mellitus
33 (10)
40 (7)
10 (33)b,e
Data for MMSE score were available for 902 patients (333 control participants, 540 patients with AD, and 29 patients with VaD).
Myocardial infarction
11 (3)
18 (3)
3 (10)
e
P < .05 vs AD.
P-tau181 MRI characteristics, No (%)
23 (77)b,e
Medical history, No (%)
9.9% (2.1%) for tau, and 9.1% (1.8%) for P-tau181, as analyzed in a high and low pool from 13 consecutive pool preparations used in total in 189 to 231 runs. The team involved in the CSF analysis was not aware of the clinical diagnoses.
APOE Genotyping For APOE genotyping, DNA was isolated from 10 mL of EDTA blood by the QIAamp DNA blood isolation kit (Qiagen). The genotype was determined with the Light Cycler APOE mutation detection kit (Roche Diagnostics GmbH). Patients were classified as APOE ε4 noncarriers or carriers. Data on APOE were available for 861 patients (94%) (327 control participants, 507 patients with AD, and 27 patients with VaD).
Data Analysis Biomarker levels of CSF were log transformed because they were not normally distributed. Differences between diagnostic categories for baseline characteristics were assessed using analysis of variance with post hoc Bonferroni corrections or Fisher exact test when applicable. Linear regression analyses were used to investigate the association between dichotomous MRI measures (independent variables) and CSF biomarker levels of Aβ42, tau, and P-tau181 (dependent variables), adjusted for age, sex, MTA, diagnosis (as categories), and interaction terms for diagnosis by MRI measure to estimate effect sizes per diagnostic group. First, separate analyses were done for MBs, WMH, and lacunes. Second, we combined the different MRI measures in 1 multivariate model to analyze independent effects on the CSF biomarker levels. Finally, we investigated the effect of APOE ε4 on the associations between the MRI measures and CSF biomarkers by adding APOE ε4 genotype and interaction terms for (1) diagnosis by MRI measures, (2) APOE ε4 genotype by MRI measure, and (3) APOE ε4 genotype by MRI measure by diagno-
sis. If there was interaction (APOE ε4 genotype by MRI measure, P
Original Investigation
Associations Between Cerebral Small-Vessel Disease and Alzheimer Disease Pathology as Measured by Cerebrospinal Fluid Biomarkers Maartje I. Kester, MD, PhD; Jeroen D. C. Goos, MD, PhD; Charlotte E. Teunissen, PhD; Marije R. Benedictus, MSc; Femke H. Bouwman, MD, PhD; Mike P. Wattjes, MD, PhD; Frederik Barkhof, MD, PhD; Philip Scheltens, MD, PhD; Wiesje M. van der Flier, PhD
IMPORTANCE It remains unclear if and how associations between cerebral small-vessel
CME Quiz at jamanetworkcme.com
disease and Alzheimer disease (AD) pathology lead to cognitive decline and dementia. OBJECTIVE To determine associations between small-vessel disease and AD pathology. DESIGN, SETTING, AND PARTICIPANTS Cross-sectional study from January 2002 to December 2012 using the memory clinic–based Amsterdam Dementia Cohort. The study included 914 consecutive patients with available cerebrospinal fluid (CSF) and magnetic resonance imaging; 547 were patients diagnosed as having AD (54% female, mean [SD], 67 [8]; Mini-Mental State Examination score, mean [SD], 21 [5]), 30 were patients diagnosed as having vascular dementia (37% female, mean [SD], 76 [9]; Mini-Mental State Examination score, mean [SD], 24 [4]), and 337 were control participants with subjective memory complaints (42% female, mean [SD], 59 [59]; Mini-Mental State Examination score, mean [SD], 28 [2]). Linear regressions were performed with CSF biomarkers (log transformed) as dependent variables and magnetic resonance imaging measures (dichotomized) as independent, adjusted for sex, age, mediotemporal lobe atrophy, and diagnosis. An interaction term for diagnosis by magnetic resonance imaging measures was used for estimates per diagnostic group. MAIN OUTCOMES AND MEASURES We examined the associations of magnetic resonance imaging white matter hyperintensities (WMH), lacunes, microbleeds with CSF β-amyloid 42 (Aβ42), total tau, and tau phosphorylated at threonine 181 (P-tau181) as well as for a subset of apolipoprotein E (APOE) ε4 carriers and noncarriers. RESULTS Microbleed presence was associated with lower CSF Aβ42 in AD and vascular dementia (standardized beta = −0.09, P = .003; standardized beta = −0.30, P = .01), and higher CSF tau in controls (standardized beta = 0.10, P = .03). There were no effects for P-tau181. The presence of WMH was associated with lower Aβ42 in control participants and patients with vascular dementia (standardized beta = −0.18, P = .002; standardized beta = −0.32, P = .02) but not in patients with AD. There were no effects for tau or P-tau181. The presence of lacunes was associated with higher Aβ42 in vascular dementia (standardized beta = 0.17, P = .07) and lower tau in AD (standardized beta = −0.07, P = .05) but there were no effects for Aβ42 or P-tau181. Stratification for apolipoprotein E genotype revealed that these effects were mostly attributable to ε4 carriers. CONCLUSIONS AND RELEVANCE Deposition of amyloid appears aggravated in patients with cerebral small-vessel disease, especially in apolipoprotein E ε4 carriers, providing evidence for pathophysiological synergy between these 3 biological factors.
JAMA Neurol. 2014;71(7):855-862. doi:10.1001/jamaneurol.2014.754 Published online May 12, 2014.
Author Affiliations: Alzheimer Center, Department of Neurology, VU University Medical Center, Amsterdam, the Netherlands (Kester, Goos, Benedictus, Bouwman, Scheltens, van der Flier); Department of Clinical Chemistry, VU University Medical Center, Amsterdam, the Netherlands (Teunissen); Department of Radiology, VU University Medical Center, Amsterdam, the Netherlands (Wattjes, Barkhof); Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, the Netherlands (van der Flier). Corresponding Author: Maartje I. Kester, MD, PhD, Alzheimer Center, Department of Neurology, VU University Medical Center, PO Box 7057, 1007 MB Amsterdam, the Netherlands ([email protected]).
855
Copyright 2014 American Medical Association. All rights reserved.
Downloaded From: http://archneur.jamanetwork.com/ by a J H Quillen College User on 06/04/2015
Research Original Investigation
Small Vessel Disease and Alzheimer Pathology
A
lzheimer disease (AD) is thought to be caused by amyloid aggregation and the formation of tau tangles.1 By contrast, in vascular dementia (VaD), infarcts or profuse white matter disease are considered the cause of cognitive decline.2 However, postmortem studies show a high prevalence of mixed pathology, especially in elderly populations.3 Many studies show cerebral small-vessel disease (SVD) and vascular risk factors to increase the risk of developing AD,4,5 while in both VaD and SVD, signs of AD pathology have been reported.6-8 It remains unclear how the interaction between SVD and AD pathology leads to dementia. Small-vessel disease could be an independent process leading to dementia in combination with coexisting yet unrelated AD pathology, but ischemic SVD might also contribute directly to AD pathology, eg, by accelerating the rate of amyloid deposition owing to ischemic changes or by inducing ischemia owing to amyloid deposition in the vessels (cerebral amyloid angiopathy [CAA]).9-12 The apolipoprotein E (APOE) ε4 genotype is a well-known risk factor not only for AD but also for cardiovascular disease and CAA, and it could be a modifying factor in the association of SVD and AD.13-17 Cerebrospinal fluid (CSF) β-amyloid 42 (Aβ42), total tau (tau), and tau phosphorylated at threonine 181 (P-tau181) are considered to reflect AD pathophysiology.18 White matter hyperintensities (WMH) and lacunes are magnetic resonance imaging (MRI) measures for ischemic SVD.2 Microbleeds (MBs) are considered a marker of underlying CAA and have also been related to hypertensive vasculopathy.9,19 By examining relationships of MRI-based MBs, WMH, and lacunes with levels of CSF Aβ42, tau, and P-tau181 in patients with AD, patients with VaD, and control participants, we explored the relationship between SVD and AD pathology. In addition, we examined the modifying effects of the APOE genotype on these relations.
Methods Study Population We included 914 consecutive patients in our study; 547 were patients diagnosed as having AD, 30 were patients diagnosed as having VaD, and 337 were control participants with subjective memory complaints from the memory clinic–based Amsterdam Dementia Cohort with available data on their CSF and MRI. All patients underwent a standard dementia screening including physical and neurological examination as well as laboratory tests, electroencephalogram, and brain MRI. Cognitive screening included Mini-Mental State Examination (MMSE) and usually involved comprehensive neuropsychological testing. The diagnosis of probable AD was made according to the National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer’s Disease and Related Disorders Association criteria20 and all patients fulfilled core clinical criteria according to National Institute on Aging– Alzheimer’s Association.21 Diagnosis of VaD was made according to the National Institute of Neurological Disorders and Stroke–Association Internationale pour la Recherche et l'Enseignement en Neurosciences criteria.2 When results of all 856
examinations were normal, patients were considered to have subjective memory complaints. Patients with mild cognitive impairment 22 or with a psychiatric disorder were not included. Diagnoses were made by consensus of a multidisciplinary team, without knowledge of CSF results or APOE genotype. Patients were asked about education, current use of medication, alcohol use, smoking history, and medical history. Diabetes mellitus was defined as use of glucoselowering agents or known history of diabetes, hypertension as use of antihypertensive agents or known history of hypertension, hypercholesterolemia as known history of hypercholesterolemia, and myocardial infarction as known history of myocardial infarction. The local institutional review board at the VU University Medical Center approved the study and all patients provided written informed consent.
MRI Assessment Scans were obtained on 4 different MRI scanners (in order of frequency): Signa 3.0-T (n = 557) (GE), Magnetom Impact 1.0-T (n = 243) (Siemens), Sonata 1.5-T (n = 77) (Siemens), Signa 1.5-T (n = 20) (GE), and Avanto 1.5-T (n = 16) (Siemens). The MRI rater was a neuroradiologist with special dementia neuroimaging expertise and was blind to clinical data. Microbleeds were defined as rounded hypointense homogeneous foci up to 10 mm in the brain parenchyma on T2*-weighted images. On the fluidattenuated inversion recovery (FLAIR) sequence, WMH were assessed using the Fazekas scale (none, punctuate, early confluent, confluent; score 0-3).23 Lacunes were defined as deep lesions from 3 to 15 mm with CSF-like signal on FLAIR, T1weighted, and T2-weighted images. Medial temporal lobe atrophy (MTA) was rated (0-4) using oblique coronal reconstructions of T1-weighted gradient-echo volume sequences perpendicular to the long axis of the hippocampus.24 Global cortical atrophy was assessed on the axial FLAIR sequence (0-3).25 On both scales, maximal atrophy is represented by the highest score. Magnetic resonance imaging readings were dichotomized as the following: MBs, 0 vs 1 or more; WMH, 0 or 1 vs 2 or 3; lacunes, 0 vs 1 or more; and MTA, (average score left and right side) 0 or 1 vs 2 or more.
CSF Analysis Cerebrospinal fluid was obtained by lumbar puncture using a 25-gauge needle and was collected in 10-mL polypropylene tubes. Within 2 hours, CSF samples were centrifuged at 1800g for 10 minutes at 4°C. A small amount of CSF was used for routine analysis including total cells, total protein levels, and glucose levels. Cerebrospinal fluid supernatant was transferred to 0.5- or 1-mL polypropylene tubes and stored at −20°C for enzyme-linked immunosorbent assay analysis within 1 month. Biomarkers of CSF were measured with Innotest sandwich enzyme-linked immunosorbent assay as previously described.26 As the manufacturer does not supply controls, the performance of the assays was monitored with pools of surplus CSF specimens. The mean (SD) intra-assay coefficient of variation was 2.0% (0.5%) for Aβ42, 3.2% (1.3%) for tau, and 2.9% (0.8%) for P-tau181 as calculated from averaging the CV of duplicates from 5 runs randomly selected over 2 years. The mean (SD) interassay coefficient of variation was 10.9% (1.8%) for Aβ42,
JAMA Neurology July 2014 Volume 71, Number 7
Copyright 2014 American Medical Association. All rights reserved.
Downloaded From: http://archneur.jamanetwork.com/ by a J H Quillen College User on 06/04/2015
jamaneurology.com
Small Vessel Disease and Alzheimer Pathology
Original Investigation Research
Table 1. Baseline Characteristicsa Control Participants (n = 337)
Characteristic Female, No. (%) Age, mean (SD), y c
Patients With AD (n = 547)
Patients With VaD (n = 30)
143 (42)
293 (54)b
11 (37)
59 (9)
67 (8)b
67 (9)b b
APOE ε4 carrier, No. (%)
111 (34)
337 (67)
13 (48)
MMSE score, mean (SD)d
28 (2)
21 (5)b
24 (4)b,e
Aβ42
893 (232)
490 (176)b
638 (233)b,e
Tau
267 (175)
692 (404)b
312 (180)e
47 (22)
89 (40)b
42 (19)e
Microbleeds present
47 (14)
117 (21)b
Lacunes present
15 (5)
40 (7)
24 (80)b,e
WMH>1
27 (8)
124 (23)b
Global cortical atrophy>1
13 (4)
MTA>1
CSF biomarker levels, mean (SD), pg/mL
Abbreviations: Aβ42, β-amyloid 42; AD, Alzheimer disease; APOE, apolipoprotein E; CSF, cerebrospinal fluid; MCI, mild cognitive impairment; MMSE, Mini-Mental State Examination; MRI, magnetic resonance imaging; MTA, mediotemporal lobe atrophy; P-tau181, tau phosphorylated at threonine 181; VaD, vascular dementia; WMH, white matter hyperintensities. a
Differences between diagnosis categories were assessed using analysis of variance with post hoc Bonferroni corrections or Fisher exact test when applicable.
25 (83)b,e
b
P < .05 vs control participants.
150 (28)b
7 (23)b
c
13 (4)
296 (54)b
16 (53)b
Data for APOE genotype were available for 861 patients (327 control participants, 507 patients with AD, and 27 patients with VaD).
Hypertension
88 (26)
172 (31)
24 (80)b,e
d
Hypercholesterolemia
63 (19)
128 (23)
13 (43)b,e
Diabetes mellitus
33 (10)
40 (7)
10 (33)b,e
Data for MMSE score were available for 902 patients (333 control participants, 540 patients with AD, and 29 patients with VaD).
Myocardial infarction
11 (3)
18 (3)
3 (10)
e
P < .05 vs AD.
P-tau181 MRI characteristics, No (%)
23 (77)b,e
Medical history, No (%)
9.9% (2.1%) for tau, and 9.1% (1.8%) for P-tau181, as analyzed in a high and low pool from 13 consecutive pool preparations used in total in 189 to 231 runs. The team involved in the CSF analysis was not aware of the clinical diagnoses.
APOE Genotyping For APOE genotyping, DNA was isolated from 10 mL of EDTA blood by the QIAamp DNA blood isolation kit (Qiagen). The genotype was determined with the Light Cycler APOE mutation detection kit (Roche Diagnostics GmbH). Patients were classified as APOE ε4 noncarriers or carriers. Data on APOE were available for 861 patients (94%) (327 control participants, 507 patients with AD, and 27 patients with VaD).
Data Analysis Biomarker levels of CSF were log transformed because they were not normally distributed. Differences between diagnostic categories for baseline characteristics were assessed using analysis of variance with post hoc Bonferroni corrections or Fisher exact test when applicable. Linear regression analyses were used to investigate the association between dichotomous MRI measures (independent variables) and CSF biomarker levels of Aβ42, tau, and P-tau181 (dependent variables), adjusted for age, sex, MTA, diagnosis (as categories), and interaction terms for diagnosis by MRI measure to estimate effect sizes per diagnostic group. First, separate analyses were done for MBs, WMH, and lacunes. Second, we combined the different MRI measures in 1 multivariate model to analyze independent effects on the CSF biomarker levels. Finally, we investigated the effect of APOE ε4 on the associations between the MRI measures and CSF biomarkers by adding APOE ε4 genotype and interaction terms for (1) diagnosis by MRI measures, (2) APOE ε4 genotype by MRI measure, and (3) APOE ε4 genotype by MRI measure by diagno-
sis. If there was interaction (APOE ε4 genotype by MRI measure, P
