David F. Andrews

University of Toronto, Toronto, Ontario, Canada

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Publications (39)269.83 Total impact

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    ABSTRACT: Dysregulation of iron homeostasis is implicated in Alzheimer's disease (AD). In this pilot study, common variants of the apolipoprotein E (APOE) and HFE genes resulting in the iron overload disorder of hereditary hemochromatosis (C282Y, H63D and S65C) were evaluated as factors in sporadic AD in an Ontario sample in which folic acid fortification has been mandatory since 1998. Laboratory studies also were done to search for genetic effects on blood markers of iron status, red cell folates and serum B12. Participants included 58 healthy volunteers (25 males, 33 females) and 54 patients with probable AD (20 males, 34 females). Statistical analyses were interpreted at the 95% confidence level. Contingency table and odds ratio analyses supported the hypothesis that in females of the given age range, E4 significantly predisposed to AD in the presence but not absence of H63D. In males, E4 significantly predisposed to AD in the absence of H63D, and H63D in the absence of E4 appeared protective against AD. Among E4+ AD patients, H63D was associated with significant lowering of red cell folate concentration, possibly as the result of excessive oxidative stress. However, folate levels in the lowest population quartile did not affect the risk of AD. A model is presented to explain the experimental findings.
    No preview · Article · May 2008 · Journal of Alzheimer's disease: JAD

  • No preview · Article · Jan 2008 · Journal of Alzheimer's disease: JAD
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    ABSTRACT: Dementia of the Alzheimer type (DAT) is common in older persons with Down syndrome (DS). There are three common alleles of the apolipoprotein E (ApoE) gene (Sigma 2, Sigma 3, and Sigma 4) resulting in three different isoforms (E2, E3, and E4) and six different genotypes (2,2; 2,3; 2,4; 3,3; 3,4; and 4,4). Sigma 4 is a risk factor for DAT whereas Sigma 2 appears prophylactic. As hepatitis B virus (HBV) infection and hypothyroidism also are common in DS, we evaluated associations between ApoE type, HBV status, and thyroid status in a sample of older persons with DS (n = 55; mean age, 44.3 +/- 10.8 years) using chi-squared analysis. Participants were classified as E2 (2,2 or 2,3), E3 (3,3), or E4 (3,4 or 4,4); positive for markers of HBV infection in the present or past (i.e., total HBcAb+ and/or HBsAg+ with or without infectivity, defined as HBV+) or negative for markers of HBV infection (defined as HBV-) and, currently receiving thyroid hormone supplement (defined as "hypothyroidism") or having normal thyroid function. The majority of the HBV+ were currently HBcAb+ and HBsAb+, but not HBsAg+. In females, there was an ApoE allele effect on thyroid status (P < or = 0.01), E2 being negatively (P < or = 0.01) and E4 being positively (P < or = 0.05) associated with "hypothyroidism". There was no evidence for an ApoE allele effect on thyroid status in males. There was no evidence for an ApoE allele effect on HBV status, or for an HBV status effect on thyroid status. As thyroid status can affect cognitive function, ApoE allele effects in DAT may, in part, be thyroid effects.
    No preview · Article · Jul 2003 · American Journal of Medical Genetics Part A
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    ABSTRACT: Familial aggregation of diseases potentially associated with metabolic syndrome (diabetes mellitus, hypertension, and cardiovascular diseases) was assessed in a colonoscopy-based case-control study of colorectal neoplasia in Toronto and Ottawa, Canada, in 1993-1996. Each familial disease was analyzed by logistic regression using generalized estimating equations. Case probands had incident adenomatous polyps (n = 172) or incident (n = 25) or prevalent (n = 132) colorectal cancer (CRC), while control probands (n = 282) had a negative colonoscopy and no history of CRC or polyps. Significant effect modification was evident in the data, with the strongest positive associations between familial diabetes and colorectal neoplasia among older probands with symptoms (parents: odds ratio (OR) = 2.4, 95% confidence interval (CI): 1.2, 4.8; siblings: OR = 5.8, 95% CI: 2.6, 13.3). Familial hypertension was also associated with colorectal neoplasia among probands with symptoms (OR = 1.7, 95% CI: 1.1, 2.6). In stratified analyses, familial diabetes, hypertension, and stroke were positively associated with adenomatous polyps in subgroups of probands who were older and/or had symptoms, while only familial diabetes was possibly associated with CRC. Associations in other proband groups may have been obscured by high cumulative incidence of parental CRC. Family studies are needed to understand the contribution of specific environmental and genetic factors in accounting for the disease aggregations.
    Full-text · Article · Nov 2002 · American Journal of Epidemiology
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    ABSTRACT: Newborns with peripheral nerve lesions involving the upper extremity are difficult to evaluate. The reliability of the Active Movement Scale (AMS), a tool for assessing motor function in infants with obstetrical brachial plexus palsy (OBPP), was examined in 2 complementary studies. Part A was an interrater reliability study in which 63 infants younger than 1 year with OBPP were independently evaluated by 2 physical therapists using the AMS. The scores were compared for reliability and controlled for chance agreement by using kappa statistics. Overall kappa analysis of the 15 tested movements showed a moderate strength of score agreement (kappa = 0.51). Quadratic-weighted kappa (kappa(quad)) statistics showed that 8 of the 15 movements tested were in the highest strength of agreement category (kappa(quad) = 0.81-1.00). Five movements showed substantial agreement (kappa(quad) = 0.61-0.80), and 2 movements had moderate agreement (kappa(quad) = 0.41- 0.60). The overall kappa(quad) was 0.89. Part B was a variability study designed to examine the dispersion of scores when infants with OBPP were evaluated with the AMS by multiple raters. Ten pediatric physical therapists with varying degrees of experience using the scale attended a 1(1/2)-hour instructional workshop on administration of the tool for infants with OBPP. A chain-block study design was used to obtain 30 assessments of 10 infants by 10 raters. A 2-way analysis of variance indicated that the variability of scores due to rater factors was low compared with the variability due to patient factors and that variation in scores due to rater experience was minimal. The results of part A indicate that the AMS is a reliable tool for the assessment of infants with OBPP when raters familiar with the scale are compared. The results of part B suggest that, with minimal training, raters with a range of experience using the AMS are able to reliably evaluate infants with upper-extremity paralysis.
    Full-text · Article · Jun 2002 · The Journal Of Hand Surgery
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    S Moalem · ME Percy · DF Andrews · TP Kruck · S Wong · AJ Dalton · P Mehta · B Fedor · AC Warren

    Preview · Article · Dec 2000 · American Journal of Medical Genetics

  • No preview · Article · Nov 2000
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    ABSTRACT: Mutations in the class I-like major histocompatibility complex gene called HFE are associated with hereditary hemochromatosis (HHC), a disorder of excessive iron uptake. We screened DNA samples from patients with familial Alzheimer disease (FAD) (n = 26), adults with Down syndrome (DS) (n = 50), and older (n = 41) and younger (n = 52) healthy normal individuals, for two HHC point mutations-C282Y and H63D. Because the apolipoprotein E (ApoE) E4 allele is a risk factor for AD and possibly also for dementia of the AD type in DS, DNA samples were also ApoE genotyped. Chi-squared analyses were interpreted at the 0.05 level of significance without Bonferroni corrections. In the pooled healthy normal individuals, C282Y was negatively associated with ApoE E4, an effect also apparent in individuals with DS but not with FAD. Relative to older normals, ApoE E4 was overrepresented in both males and females with FAD, consistent with ApoE E4 being a risk factor for AD; HFE mutations were overrepresented in males and underrepresented in females with FAD. Strong gender effects on the distribution of HFE mutations were apparent in comparisons among ApoE E4 negative individuals in the FAD and healthy normal groups (P < 0.002). Our findings are consistent with the proposition that among ApoE E4 negative individuals HFE mutations are predisposing to FAD in males but are somewhat protective in females. Further, ApoE E4 effects in our FAD group are strongest in females lacking HFE mutations. Relative to younger normals there was a tendency for ApoE E4 and H63D to be overrepresented in males and underrepresented in females with DS. The possibility that HFE mutations are important new genetic risk factors for AD should be pursued further.
    No preview · Article · Jul 2000 · American Journal of Medical Genetics
  • David F. Andrews · James E. Stafford
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    ABSTRACT: Algebraic calculations that depend upon a full partition can be automated through the use of an operator P for the derivation of such a partition. Calculations that require the repeated use of P are automated by simply iterating the operator. The resulting output is general and contains sufficient structure to identify the result of a calculation for a variety of settings.
    No preview · Article · Aug 1998 · Statistics and Computing
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    ABSTRACT: The aim of this study was to determine the risk of endoscopic/radiological recurrence of Crohn's disease postoperatively and the long-term outcome. A randomized placebo-controlled trial was performed to determine the effectiveness of mesalamine in preventing recurrent Crohn's disease postoperatively. Patients in the control group were examined endoscopically/radiologically before entry into and annually during the trial. Findings were classified as minimal or severe. There were 76 patients (49 men and 37 women; mean age, 37.1 +/- 13.2 years). Fifty (61.7%) had terminal ileal resections. Overall, 55 endoscopic/radiological recurrences were observed in 51 patients (67.1%). Expressed actuarially, the recurrence rate was 27.5% at 1 year (95% confidence interval [CI], 15.8%-37.6%), 60.8% at 2 years (95% CI, 46%-71.3%), and 77.3% at 3 years (95% CI, 62.7%-86.3%). Nineteen (37%) were symptomatic and 12 (24%) were initially asymptomatic but later became symptomatic (mean, 13.0 +/- 8.8 months), whereas 20 (39%) remained asymptomatic (mean, 16.9 +/- 17.4 months). Patients with severe endoscopic/radiological disease were significantly more likely to be or become symptomatic than those with minimal disease (23 of 32 vs. 8 of 19, respectively; P = 0.0437). This study suggests that postoperative endoscopic/radiological recurrences occur later than previously reported. Furthermore, many of these patients, especially with minimal disease, will remain asymptomatic.
    No preview · Article · Jan 1998 · Gastroenterology
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    ABSTRACT: Recurrence of Crohn's disease frequently occurs after surgery. A randomized controlled trial was performed to determine if mesalamine is effective in decreasing the risk of recurrent Crohn's disease after surgical resection is performed. One hundred sixty-three patients who underwent a surgical resection and had no evidence of residual disease were randomized to a treatment group (1.5 g mesalamine twice a day) or a placebo control group within 8 weeks of surgery. The follow-up period was a maximum of 72 months. The symptomatic recurrence rate (symptoms plus endoscopic and/or radiological confirmation of disease) in the treatment group was 31% (27 of 87) compared with 41% (31 of 76) in the control group (P = 0.031). The relative risk of developing recurrent disease was 0.628 (90% confidence interval, 0.40-0.97) for those in the treatment group (P = 0.039; one-tail test) using an intention-to-treat analysis and 0.532 (90% confidence interval, 0.32-0.87) using an efficacy analysis. The endoscopic and radiological rate of recurrence was also significantly decreased with relative risks of 0.654 (90% confidence interval, 0.47-0.91) in the effectiveness analysis and 0.635 (90% confidence interval, 0.44-0.91) in the efficacy analysis. There was only one serious side effect (pancreatitis) in subjects in the treatment group. Mesalamine (3.0 g/day) is effective in decreasing the risk of recurrence of Crohn's disease after surgical resection is performed.
    No preview · Article · Sep 1995 · Gastroenterology

  • No preview · Article · Apr 1995 · Gastroenterology
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    ABSTRACT: Obstetrical brachial plexus palsy remains an unfortunate consequence of difficult childbirth. Sixty-six such patients were reviewed. Included were 28 patients (42 percent) with upper plexus involvement and 38 (58 percent) with total plexopathy. The natural history of spontaneous recovery in all of these patients has been determined using an appropriate grading mechanism. Sixty-one patients (92 percent) recovered spontaneously and five patients (8 percent) required primary brachial plexus exploration and reconstruction (median age 12 months), demonstrating that most patients do well. Additional analysis was undertaken to examine ways in which outcome might be predicted. The analysis does not consider whether or not the patient was operated upon. Good or poor recovery was determined by the spontaneous recovery observed. Discriminant analysis revealed that whereas elbow flexion at 3 months correlated well with spontaneous recovery at 12 months, when used as a single parameter it incorrectly predicted recovery in 12.8 percent of cases. Shoulder abduction was not a significant predictor of recovery. Numerous other early parameters correlated well with spontaneous recovery. When elbow flexion and elbow, wrist, thumb, and finger extension at 3 months were combined into a test score, the proportion of patients whose recovery was incorrectly predicted was reduced to 5.2 percent.
    No preview · Article · May 1994 · Plastic & Reconstructive Surgery

  • No preview · Article · Apr 1994
  • James E. Stafford · David F. Andrews · Yong Wang
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    ABSTRACT: We describe a set of procedures that automate many algebraic calculations common in statistical asymptotic theory. The procedures are very general and serve to unify the study of likelihood and likelihood type functions. The procedures emulate techniques one would normally carry out by hand; this strategy is emphasised throughout the paper. The purpose of the software is to provide a practical alternative to difficult manual algebraic computations. The result is a method that is quick and free of clerical error.
    No preview · Article · Jan 1994 · Statistics and Computing
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    ABSTRACT: SUMMARY A symbolic algorithm for the derivation of the asymptotic expansion of the maximum likelihood estimate was first introduced by Andrews & Stafford (1993). This algorithm is quite general and can be modified to give asymptotic expansions for the maximum likelihood estimate based on either the conditional, modified or adjusted profile likelihoods. Expansions are obtained quickly with no chance for human clerical error. As a result, these three adjustments can be easily studied and some new statistical results are obtained. Bartlett corrections of each adjusted likelihood, and asymptotic expansions for the first four moments of the maximum likelihood estimate based on the conditional and adjusted profile likelihoods, are derived.
    No preview · Article · Dec 1993 · Biometrika
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    ABSTRACT: We previously observed low level mosaicism (2-4% normal cells) in phytohemagglutinin-stimulated peripheral blood lymphocytes (PBL) in 29% of a small group of elderly persons with Down syndrome (DS). An analysis of cytogenetic data on 154 trisomy 21 cases (age 1 day to 68 years) showed that the proportion of diploid cells in such cultures significantly increased (P < 0.005) with advancing age. Thus, the "occult" mosaicism in PBL of the elderly persons with DS is likely due to the accumulation of cells that have lost a chromosome 21. A consequence of chromosome 21 loss could be uniparental disomy of the 2n cells, a factor that might have significant biological consequences if some chromosome 21 genes are imprinted. Loss of a chromosome 21 from trisomic cells might result in tissue-specific mosaicism and "classical" mosaicism in different age groups. Chromosome 21 loss might also be relevant to the development of Alzheimer-type dementia in DS and in the general population.
    No preview · Article · Mar 1993 · American Journal of Medical Genetics
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    ABSTRACT: Probable Alzheimer disease (AD) is described in 79-year-old male twins with monozygosity confirmed by DNA examination. The first twin to be affected began to show signs of intellectual deterioration at age 70. In the other, onset was at age 72. Four of their living sibs (current age range = 75-92) are also suspected to have AD. The possible roles of genetic and environmental factors in the development of AD in this sibship are discussed.
    No preview · Article · Nov 1992 · American Journal of Medical Genetics
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    Full-text · Article · Aug 1991 · The Lancet
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    ABSTRACT: Although epidemiological and biochemical evidence suggests that aluminium may be associated with Alzheimer's disease (AD), there is no convincing proof of a causal link for aluminium in disease progression. We have completed a two year, single-blind study to investigate whether the progression of dementia could be slowed by the trivalent ion chelator, desferrioxamine. 48 patients with probable AD were randomly assigned to receive desferrioxamine (125 mg intramuscularly twice daily, 5 days per week, for 24 months), oral placebo (lecithin), or no treatment. No significant differences in baseline measures of intelligence, memory, or speech ability existed between groups. Activities of daily living were assessed and videorecorded at 6, 12, 18, and 24 month intervals. There were no differences in the rate of deterioration of patients receiving either placebo or no treatment. Desferrioxamine treatment led to significant reduction in the rate of decline of daily living skills as assessed by both group means (p = 0.03) and variances (p less than 0.04). The mean rate of decline was twice as rapid for the no-treatment group. Appetite (n = 4) and weight (n = 1) loss were the only reported side-effects. We conclude that sustained administration of desferrioxamine may slow the clinical progression of the dementia associated with AD.
    No preview · Article · Jul 1991 · The Lancet

Publication Stats

2k Citations
269.83 Total Impact Points


  • 1978-2008
    • University of Toronto
      • • Department of Physiology
      • • Department of Surgery
      • • Department of Obstetrics and Gynaecology
      • • Department of Clinical Sciences
      • • Department of Mathematics
      Toronto, Ontario, Canada
  • 1982-2002
    • SickKids
      • Department of Rehabilitation Services
      Toronto, Ontario, Canada
  • 1998
    • Mount Sinai Hospital, Toronto
      Toronto, Ontario, Canada