Yarnall et al e1
Appendix e-1
Mild Cognitive Impairment in incident Parkinson’s disease: The ICICLE-PD Study
e-Methods
We attempted to identify every new case of Parkinson’s disease (PD) within Cambridgeshire and Newcastle upon Tyne/Gateshead from 1st June 2009 to 31st December 2011, including all patients presenting with any extrapyramidal symptoms and signs (tremor, rigidity, bradykinesia, micrographia, loss of dexterity, hypomimia, reduced arm-swing, or parkinsonian gait). In addition, patients with a new diagnosis of parkinsonism attending clinics in the surrounding areas were asked by their local PD specialist if they wished to be contacted by the study team for further assessment and evaluation. A total of 166 primary care practices were identified and encouraged to refer patients with suspected parkinsonism. We also informed colleagues in secondary care and invited them to refer all patients with suspected parkinsonism. This group included neurologists (n=48), geriatricians (n=17), and Parkinson’s disease nurse specialists (n=14). Exclusion criteria comprised: parkinsonism prior to the onset of the study; insufficient working knowledge of English (defined as insufficient to perform the neuropsychological assessments or questionnaires in the opinion of the assessor); dementia at presentation (defined as MMSE score < 24 in keeping with earlier studiese1-3), or meeting DSM IV criteria for dementia or the Movement Disorder Society (MDS) criteria for dementia;e4 subjects who did not have the capacity to give informed consent; history consistent with Dementia with Lewy Bodies (DLB),e5 atypical parkinsonian syndromes (including multiple system atrophy or progressive supranuclear palsy, diagnosed according to accepted criteriae6) repeated strokes or stepwise progression of symptoms, leading to a diagnosis of ‘vascular parkinsonism’; and, exposure to dopamine receptor blocking agents at the onset of symptoms. Functional independence of participants was determined through semi-structured interviews with carers and/or subjects.
Age-matched controls were recruited through local advertising (including primary care settings), word of mouth and community groups to provide a comparative group. However, carers, spouses and relatives of patients with PD were not permitted in order to limit bias in terms of symptom reporting and disease burden. None of the controls had a history of major psychiatric disorder, were cognitively impaired, had had a stroke or a movement disorder. Controls were unselected and not pre-screened for cognitive impairment: this increases their representativeness and generalizability to the general population. All control subjects underwent clinical and neuropsychological testing, and were given the option of participating in laboratory and MRI studies. Global cognitive scores in control participants were comparable to published age- and educationally-matched normative data for the MMSEe7 and Montreal Cognitive Assessment (MoCA).e8 Thus, mean age of our controls was 67.9 years with a mean of 13.1 years of education and a median MMSE of 29.0; a median MMSE value based on population norms in the 65-69 age category with ≥12 years of education is 29.e7 Similarly, mean MoCA in our control participants was 27.0, comparable to a score of 27.2 in a group of healthy controls where mean age was 67.3 with 13.7 years of education. e8
Clinical and Neuropsychological Assessment
Motor phenotype was calculated using the MDS-UPDRS revisione9 of the method described by Jankovic, e10 whereby patients are categorised into tremor dominant (TD), postural instability with gait difficulty (PIGD), or indeterminate motor subtypes based on the ratio between mean tremor score versus mean postural instability gait difficulty score. Levodopa equivalent dose was calculated for all dopaminergic medications.e11 As part of the memory domain within cognitive testing, Pattern Recognition Memory (PRM), Spatial Recognition Memory (SRM) [differentially sensitive to impairment of temporal and frontal lobe function, respectivelye12] and Paired Associates Learning (PAL) from the computerised CANTAB batterye13-15 were assessed. Paired associates learning is a visuospatial test of learning and memory that is sensitive to both temporal and frontal damage and has been shown to predict Alzheimer's disease 32 months before formal diagnosis in memory clinic or in the community. e16, 17 Executive function testing included the modified ('one touch stocking') version (OTS) of the Tower Of London task from the CANTAB battery, a test of planning requiring working memorye15 that has been shown to activate fronto-parietal-caudate circuitry. e18, 19 For PRM and SRM, total number of correct answers was measured. In PAL, the mean number of trials to success was used, and for OTS, the number of problems solved on first choice was chosen. MoCA was not performed on the first 24 participants as it was introduced later in the study. A small number of subjects did not undergo all 11 neuropsychological tests and were coded as missing data (table e-2). For example, the Cognitive Drug Research computerized battery could not be completed in two PD patients due to technical issues.
For the entire neuropsychological battery, a test score was considered ‘impaired’ if it was 1, 1.5 or 2 standard deviations (SD) below the mean score of the control subjects which were normally distributed. For non-normally distributed data, even after transformation, cut-offs were used that gave approximately the correct percentage of controls falling in the “impaired” range (according to the normal distribution) for that corresponding SD.
Cerebrospinal fluid (CSF) analysis
Samples were analysed using commercially available assays (tau protein: INNOTEST hTAU Antigen; p-tau: INNOTESTTM PHOSPHO-TAU(181P); Aß42: INNOTEST TH ß-AMYLOID (1-42) all Fujirebio Inc/Innogenetics, Gent, Belgien; p-tau and Aß40: hAmyloid ß40 Elisa ABETA GmbH, Heidelberg, Germany). e20 CSF α-synuclein (αsyn) values were determined as published previously with slight modifications. e21, 22 Capture antibody MJF-1 clone 12.1 (kindly provided by Liyu Wu, Epitomics, Burlingame, CA, USA) was used at 3µg/ml. Detection was performed using Anti-α-Synuclein clone 42/α-Synuclein (BD Biosciences, Heidelberg, Germany) at 1µg/ml.
Of the entire sample, 67 PD participants consented to lumbar puncture and all samples were used in the analyses. The sample was representative in terms of clinical, cognitive and demographic features (table e-3). Those who did not consent tended to have higher depression scores (3.1 vs. 2.4, p=0.025) and lower educational levels (12.5 vs. 13.5, p=0.035), although these tests were not corrected for multiple comparisons and therefore are not meaningful.
MRI statistical analysis
Regional grey matter volume differences were assessed using the SPM8 general linear model based on random Gaussian field theory. An absolute threshold mask of 0.05 was used for the grey matter analyses. Significant effects were assessed using a voxelwise uncorrected threshold of p ≤ 0.001 and clusters regarded as significant if they were larger than 100 voxels and with a family-wise error (FWE) threshold of p ≤ 0.05, corrected for multiple comparisons. Age and intracranial volume were included as covariates.
Statistical analysis
The primary statistical analysis consisted of descriptive statistics comparing those classified as MCI level 1 or level 2 with the PD-cognitively normal (CN) groups, and within MCI level 2, whether they met the criteria at 1, 1.5 or 2 SD below normative values. Further statistical analysis was then performed using PD participants classified at level 2 MCI at 1.5 SDs below normative values to compare genetic, CSF and imaging data to reduce the risk of a type I error. A p value of < 0.05 was deemed as significant, and all p values reported are two-tailed. A priori correction for multiple comparisons was not made due to the nature of our investigation; if a parameter was significant, even if by chance, we felt it merited further analysis.e23-26 However, if required after further examination of the clinical significance, a Bonferroni correction was applied for multiple comparisons.
Yarnall et al e1
e-References
e1. Foltynie T, Brayne CEG, Robbins TW, Barker RA. The cognitive ability of an incident cohort of Parkinson’s patients in the UK. The CamPaIGN study. Brain 2004;127:550-60.
e2. Muslimovic D, Post B, Speelman JD, Schmand B. Cognitive profile of patients with newly diagnosed Parkinson disease. Neurology 2005;65:1239-45.
e3. Elgh E, Domellof M, Linder J, Edstrom M, Stenlund H, Forsgren L. Cognitive function in early Parkinson's disease: a population-based study. Eur J Neurol 2009;16:1278-84.
e4. Emre M, Aarsland D, Brown R, et al. Clinical diagnostic criteria for dementia associated with Parkinson's disease. Mov Disord 2007;22:1689-707.
e5. McKeith IG, Dickson DW, Lowe J, et al. Diagnosis and management of dementia with Lewy bodies: third report of the DLB Consortium. Neurology 2005;65:1863-72.
e6. Litvan I, Bhatia KP, Burn DJ, et al. SIC Task Force appraisal of clinical diagnostic criteria for Parkinsonian disorders. Mov Disord 2003;18:467-486.
e7. Crum RM, Anthony JC, Bassett SS, Folstein MF. Population-based norms for the Mini-Mental State Examination by age and educational level. JAMA 1993;269:2386-91.
e8. Dalrymple-Alford JC, MacAskill MR, et al. The MoCA: well-suited screen for cognitive impairment in Parkinson disease. Neurology 2010;75:1717-25.
e9. Goetz CG, Tilley BC, Shaftman SR, et al. Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS): scale presentation and clinimetric testing results. Mov Disord 2008;23:2129-2170.
e10. Stebbins G, Goetz CG, Burn DJ, Jankovic J, Tilley BC. Postural instability and gait difficulty scores from the MDS-UPDRS. Mov Disord 2011;26:A1077.
e11. Tomlinson CL, Stowe R, Patel S, Rick C, Gray R, Clarke CE. Systematic review of levodopa dose equivalency reporting in Parkinson's disease. Mov Disord 2010;25:2649-2653.
e12. Owen AM, Sahakian BJ, Semple J, Polkey CE, Robbins TW. Visuo-spatial short-term recognition memory and learning after temporal lobe excisions, frontal lobe excisions or amygdalo-hippocampectomy in man. Neuropsychologia 1995;33:1-24.
e13. Robbins TW, James M, Owen AM, Sahakian BJ, McInnes L, Rabbitt P. Cambridge Neuropsychological Test Automated Battery (CANTAB): a factor analytic study of a large sample of normal elderly volunteers. Dementia (Basel, Switzerland) 1994;5:266-281.
e14. Sahakian BJ, Morris RG, Evenden JL, et al. A comparative study of visuospatial memory and learning in Alzheimer-type dementia and Parkinson's disease. Brain : a journal of neurology 1988;111 ( Pt 3):695-718.
e15. Owen AM, Sahakian BJ, Hodges JR, Summers BA, Polkey CE, Robbins TW. Dopamine-Dependent Frontostriatal Planning Deficits in Early Parkinsons-Disease. Neuropsychology 1995;9:126-140.
e16. Blackwell AD, Sahakian BJ, Vesey R, Semple JM, Robbins TW, Hodges JR. Detecting dementia: novel neuropsychological markers of preclinical Alzheimer's disease. Dement Geriatr Cogn 2004;17:42-48.
e17. Swainson R, Hodges JR, Galton CJ, et al. Early detection and differential diagnosis of Alzheimer's disease and depression with neuropsychological tasks. Dement Geriatr Cogn 2001;12:265-280.
e18. Baker SC, Rogers RD, Owen AM, et al. Neural systems engaged by planning: A PET study of the Tower of London task. Neuropsychologia 1996;34:515-526.
e19. Cheesman AL, Barker RA, Lewis SJG, Robbins TW, Owen AM, Brooks DJ. Lateralisation of striatal function: evidence from F-18-dopa PET in Parkinsion's disease. J Neurol Neurosur Ps 2005;76:1204-1210.
e20. Mollenhauer B, Bibl M, Wiltfang J, et al. Total tau protein, phosphorylated tau (181p) protein, beta-amyloid(1-42), and beta-amyloid(1-40) in cerebrospinal fluid of patients with dementia with Lewy bodies. Clin Chem Lab Med 2006;44:192-195.
e21. Mollenhauer B, Cullen V, Kahn I, et al. Direct quantification of CSF alpha-synuclein by ELISA and first cross-sectional study in patients with neurodegeneration. Exp Neurol 2008;213:315-325.
e22. Kruse N, Schulz-Schaeffer WJ, Schlossmacher MG, Mollenhauer B. Development of electrochemiluminescence-based singleplex and multiplex assays for the quantification of alpha-synuclein and other proteins in cerebrospinal fluid. Methods 2012.
e23. Rothman KJ. No adjustments are needed for multiple comparisons. Epidemiology 1990;1:43-6.
e24. Perneger TV. What's wrong with Bonferroni adjustments. BMJ 1998; 316: 1236-8.
e25. Feise RJ. Do multiple outcome measures require p-value adjustment? BMC Med Res Methodol. 2002;2:8.