C63 OCCUPATIONAL RISK FACTORS IN SPORADIC ALS: A SYSTEMATIC REVIEW
Sutedja NA, Veldink JH, Wokke JHJ, van den Berg LH
University Medical Centre Utrecht, Utrecht, The Netherlands
E‐mail address for correspondence: [email protected]
Background: A large number and variety of studies have been performed in the search for exogenous risk factors in sporadic ALS, often producing conflicting results. Most reviews of these studies, however, are narrative and few have used a systematic approach in defining inclusion criteria and comparing study methodology.
Objective: To perform a systematic review of occupational risk factors in sporadic ALS.
Methods: An extensive search strategy was designed and run in the Medline, Embase, Cinahl, and Cochrane databases. A study was included if the following criteria were met: it had to 1) be a case control or cohort study; 2) examine occupations in patients with sporadic ALS and a reference group; 3) not be performed in study populations in Guam, the Kii Peninsula or other endemic areas. Included studies were appraised according to a classification of evidence developed for risk factors in ALS by Armon. Each occupation studied was grouped according to the International Standard Classification of Occupations (ISCO‐88) and for each occupational category available study findings were summarized.
Results: The search strategy provided 3773 potentially relevant studies. After screening of title, abstract, and full‐text articles according to the selection criteria, 56 studies were included: three cohort, 24 case‐control, 16 mortality cohort, and 13 mortality case‐control studies. Studies making use of mortality registers were grouped separately. Most of these studies fell into Armon's level of evidence class III or IV. One hundred and thirty different major and minor occupational groups were examined in one or more studies. Studies differed with regard to design, the types of measures of association computed, and the occupational categories studied. Because of this heterogeneity, quantitative pooling per occupational group was impossible. To summarize the data, the vote counting method was applied. A minority of the occupations studied had a positive vote count. These were power plant operators, veterinarians, health associate professionals, athletes, hairdressers, and potters.
Conclusion: Multiple studies were performed for individual occupations, often giving conflicting results. The methodological quality of the studies did not exceed Armon's level of evidence class III. Most studies did not fall into higher categories because of the testing of multiple hypotheses, the presence of small numbers of individuals with ALS with a specific occupational exposure, and selection bias. Well‐designed large prospective cohort studies are needed focusing on a few occupations. Bearing the limitations of study quality in mind, this review concludes that the most promising occupations are power plant operators, veterinarians, health associate professionals, athletes, hairdressers, and potters. Unfortunately, there is no common underlying mechanism for developing ALS that can be explained by these occupations. A job‐exposure matrix can elucidate specific occupational exposures and be utilized in future studies.
C64 INCIDENCE OF AMYOTROPHIC LATERAL SCLEROSIS IN LOMBARDY, ITALY
Beghi E1, Millul A1, Micheli A2, Vitelli E3, Logroscino G4
1Instituto Mario Negri, Milano, Lombardy, Italy, 2Fondazione Maugeri, Gussago, Lombardy, Italy, 3Azienda Ospedaliera di Lodi, Lodi, Lombardy, Italy, 4SPH Harvard University, Boston, MA, USA
E‐mail address for correspondence: [email protected]
Background: The incidence and trends of amyotrophic lateral sclerosis (ALS) have been mostly assessed in small population samples. Data from well‐defined large populations at risk are limited.
Objective: To define the incidence, time and geographic trends of ALS in Lombardy, northern Italy, through a population‐based register.
Methods: This study was performed in nine provinces of Lombardy (population 4,947,554). Patients with newly diagnosed ALS were enrolled during the calendar years 1998–2002. The main source of cases was a prospective regional register of ALS, started on 1 January 1998. The register was based on a network of caring neurologists from neurological, neurophysiological and rehabilitation units in the study area. Cases were also traced through the Hospital Discharge Diagnosis (HDD) code 335.2 (MND) at the Central Regional Archive.
For each eligible patient, the caring physician was required to collect the main demographic and clinical information in a semi‐structured form. A panel of experts reviewed all forms and each eligible patient was classified as definite, probable, probable ‐ laboratory supported, possible or suspected ALS, according to a combination of the original and revised El Escorial diagnostic criteria. Overall crude, age and sex‐adjusted mean annual incidence rates were calculated for the entire study population and for each year and province separately. Age specific incidence rates were also provided. Age‐ and sex‐adjustment was made with the direct method of standardization using the 2001 Italian population for reference.
Results: During the study period we collected data on a total of 517 patients (293 male, 224 female; male:female ratio 1.3) aged 18–92 years at diagnosis (mean 63.6 years). Onset of symptoms was bulbar in 29% of cases. ALS was definite in 45%, probable in 27%, probable ‐ laboratory supported in 3.5%, possible in 15%, and suspected in 10% of cases. Mean disease duration at diagnosis was 10.6 months. The standardized incidence ratio was 2.10 per 1,000,000/year (95% CI 1.19–3.19). The ratio was 2.43 in men and 1.76 in women, tended to increase with age up to the years 70–74, and to decrease thereafter. The rate was virtually unchanged in each year of the study period and presented moderate variations when comparing the different provinces. The incidence of definite ALS was 0.93 per 100,000. The incidence of spinal‐onset ALS was 1.35 and that of bulbar‐onset ALS was 0.60. The rate was consistently higher in men with spinal‐onset ALS, peaking at age 75–79 years compared to men with bulbar‐onset ALS and women. In the latter, the rate tended to overlap when comparing spinal‐onset to bulbar‐onset ALS. The disease peaked at age 70–74 years in women and fluctuated at age 65–69 years through age 80–84 years in men with bulbar‐onset ALS.
Discussion and conclusions: This study confirms a steady incidence ratio of ALS over a five‐year period, with no evidence of significant temporal and geographic clusters. The age‐specific incidence of the disease tends to vary according to the site of onset.
C65 A META‐ANALYSIS OF THE INCIDENCE OF AMYOTROPHIC LATERAL SCLEROSIS IN EUROPE: THE EURALS COLLABORATIVE STUDY
Logroscino G, Traynor B, Hardiman O, Chio A, Mitchell D, Swingler R, Millul A, Beghi E
Harvard School of Public Health, Boston, USA
E‐mail address for correspondence: [email protected]
Background: Recent population‐based prospective studies have shown that the incidence of ALS is uniform across Europe. However, a number of important questions remain unanswered: Does the incidence of ALS continue to increase among the very elderly? Is the risk of developing ALS in females approaching that of males? Existing registers are unable to definitively answer these questions due to their limited catchment populations of approximately 4 million each. EURALS is a collaborative effort designed to unify the six existing European ALS registers and to provide useful epidemiological data for a large population across Europe. We present the results of a meta‐analysis of the epidemiology of ALS in a cohort of 17 million for the years 1998 and 1999.
Objectives: 1) To determine the incidence and distribution of bulbar and spinal subtypes of ALS across Europe; 2) to investigate if the incidence of ALS continues to increase among the very elderly age groups (i.e. 75 years old, plus); 3) to evaluate if the risk of ALS is increasing among women compared to men.
Methods: Incidence data for the time period 1 January 1998 to 31 December 1999 were available from six studies carried out in three European countries, three from Italy (Piemonte, Lombardia, Puglia), one, respectively, from Scotland, England (Lancashire), and Ireland. The diagnosis of ALS was based on the first version of the El Escorial criteria (EEC). These data were pooled and age‐ and sex‐specific incidence rates were calculated as the number of new cases divided by the person‐years at risk. Population denominators were obtained from local government censuses.
Results: Data were available from 34,167,244 person‐years representing a population of 17,083,622 (Ireland 3,703,100, Piemonte 4,407,782, Lombardia 4,947,554, Puglia 4,025,186). Six hundred and ninety‐seven incident cases were diagnosed during the two year study period 1998–1999 (317 females (45.5 %) and 380 males (54.5%); 361 cases in 1998 and 336 cases in 1999). The crude incidence of ALS was 2.04 per 100,000 person‐years. Nearly two‐thirds of cases were of spinal onset (65.9%), the remainder being classified as bulbar onset (29.1%), generalized onset (4.3%) and unspecified (0.7%). Men had a higher incidence of ALS than women during this time period (2.3 and 1.8 per 100,000). Incidence increased steeply with age, being 0.25 per 100,000 below the age of 45 years, 3.4 among the 45–70 years age group, and 5.9 after age 70+ years.
Conclusions: This is the first meta‐analysis of ALS epidemiological data and represents the largest reference population presented to date.
C66 ANGIOGENIN POLYMORPHISMS MODIFY AGE AT ONSET IN SPORADIC ALS
Khan H, Saeed M, Chen W, Siddique N, Hung WY, Siddique T
Northwestern University, Chicago, IL, USA
E‐mail address for correspondence: [email protected]
Background: Variations in angiogenin (ANG), a hypoxia‐inducible gene, have been implicated as risk factors for motor neuron degeneration (1).
Objectives: To investigate the association and modifier effects of ANG gene polymorphisms with sporadic ALS (SALS) in a family‐based and case‐control cohort.
Methods: We investigated the association of ANG gene polymorphisms in a large North American Caucasian family‐based and case‐control cohort (n = 1987). Genotyping was performed using TaqMan® SNP Genotyping Assays. Data were analysed using SPSS, FBAT and Haploview. We genotyped three SNPs (rs1010461, hCV2742351, rs11701) spanning the ANG gene including the synonymous polymorphism which was earlier found to be associated with ALS in the Irish and Scottish populations (1).
Results: The T allele of rs11701 was associated with SALS in the trio group (p = 0.0027) and the pedigree model (p = 0.033). There was no association in the discordant sib‐pair or case‐control models. Haplotype analysis of the three SNPs in the trio model revealed that the A‐C‐G haplotype was protective (p = 0.0058) whereas the A‐C‐T haplotype was associated with increased risk of disease (p = 0.045).
The GG genotype of rs11701 advanced the age at onset of SALS by 14.2 years compared with the GT and TT genotypes on Kaplan‐Meier analysis (Log‐rank = 4.96, p = 0.026). In contrast, the AA genotype of rs1010461 was associated with an earlier age at onset of disease (Log‐rank = 4.12, p = 0.042).
Conclusions: Our findings are contrary to those reported earlier and implicate the T allele of rs11701 as the detrimental allele for SALS in North America. The evidence suggests that ANG is a modifier gene for SALS and plays a significant role in affecting the age at onset of disease.
Acknowledgements: We thank the patients with ALS and their families for their participation in this study. Without their help this work would not have been possible. This research was supported by NINDS (NS050641, NS046535), Les Turner ALS Foundation, V.E. Schaff ALS Research Fund, H. Post Research Professorship, Wenske Foundation, Falk Medical Research Trust, Les Turner ALS Foundation / Herbert C. Wenske Foundation Professorship and The David C. Asselin MD Memorial Fund.
References
- Greenway MJ, Andersen PM, Russ C, et al. Nat Genet. 2006;38:411–3.
C67 EVALUATION OF LINKAGE OF ALS/FTD TO CHROMOSOME 9Q WITH THE ESTABLISHMENT OF NEW LINKAGE TO 9P21
Yan J1, Siddique N1, Slifer S2, Bigio E1, Chen W1, Mao H1, Liu E1, Shi Y1, Khan S1, Haines J3, Pericak‐Vance M2, Siddique T1
1Northwestern University Feinberg School of Medicine, Chicago, IL, USA, 2Duke University Medical Center, Durham, USA, 3Vanderbilt University Medical Center, Nashville, TN, USA
E‐mail address for correspondence: [email protected]
Background: ALS, a clinically and genetically heterogeneous disease with several genetic loci identified, is sometimes associated with frontotemporal dementia (FTD). FTD constitutes a degenerative disorder of the frontal and temporal lobes with onset of symptoms between the ages of 35 and 75 years and accounts for 12.5–16.6% of all primary degenerative dementias. FTD is now well recognized in ALS, and ALS could be associated with dementia with an incidence varying from 3% to 15%. Previous reports of linkage of ALS/FTD to 9q21 have not been verified by subsequent studies.
Objectives: To ascertain the linkage of ALS/FTD.
Methods: Fifteen ALS/FTD families were included in an affected relative pair analysis of 43 SOD1 negative ALS and ALS/FTD families which were screened with 405 fluorescent‐labelled MapPairs® human DNA markers covering the entire genome at 20 cM. Additional microsatellite markers were selected for dense mapping under peaks with lod scores >1. Genotyping and sequencing were both performed on Beckman Coulter CEQ 8000 Genetic Analysis Systems. Two‐point and two‐point heterogeneity LOD score (HLOD) analyses were computed using FASTLINK and multipoint analyses were analysed by SIMWALK.
Results: There were 80 affected individuals, of which 49 subjects were genotyped. Three families with positive scores on 9q21 were excluded from that locus. No mutations were detected in the Tau gene or the VCP and 92 genes. The ARP screen suggested linkage to 9p. Detailed genotyping on chromosome 9 showed a location score of 5.36 at 51.53 cM, and a Hetlod of 9.9 at 51.06 cM by Simwalk. The multipoint LOD score and multipoint heterogeneity score returned by Fastlink overlapped with each other at 47.57 cM with identical value of 7.74. The maximum two‐point LOD score returned by Fastlink was 6.8 at D9S259 for the fifteen ALS/FTD families. Based on LOD scores and haplotype analysis 9 out of 15 ALS/FTD families were linked to 9p21. F638, F9969 and F9748 were all possibly linked to this new locus. A centromeric crossover between D9S1678 and D9S259 was found in F8462 and F9029 and a telemetric crossover between D9S1846 and D9S1684 was present in F8462, F7810 and F638, which defines the MCR of the new locus being 12.49 cM on 9p21 flanked by D9S1684 and D9S1678. Two brains were available for pathological evaluation, and they showed remarkable circumscribed frontal and temporal atrophy, neuronal loss and gliosis and ubiquitin skein‐like and Lewy‐like inclusions in anterior horn neurons and cytoplasmic neuronal inclusions in hippocampal dentate gyrus.
Discussion and conclusions: The linkage of ALS/FTD to 9q was not validated and robust evidence for a major novel locus on 9P21 for ALS/FTD was obtained. Efforts are underway to identify the gene defect.
Acknowlegements: These studies were supported by grants from the National Institutes of Health, (NINDS:NS050641, NS046535), Les Turner ALS Foundation, Playing to Win 4 Life Foundation, V. E. Schaff ALS Research Fund, H. Post Research Professorship, Wenske Foundation, Falk Medical Research Trust, The Les Turner ALS Foundation/Herbert C. Wenske Foundation Professorship, and The David C. Asselin MD Memorial Fund and The Muscular Dystrophy Association.
C68 COMPREHENSIVE ANALYSIS OF CAUSATIVE AND RELATED GENES FOR ALS USING A HIGH THROUGHPUT DNA MICROARRAY‐BASED RESEQUENCING SYSTEM
Takahashi Y, Goto J, Tsuji S
The University of Tokyo, Tokyo, Japan
E‐mail address for correspondence: [email protected]
Background: The list of causative genes for familial ALS (FALS) has been expanding in accordance with the recent progress in molecular genetics. Alterations of these genes may be correlated with the pathogenesis of sporadic ALS due to reduced penetrance of the mutations. Furthermore, some alterations may contribute to ALS as disease susceptibility genes. Under this situation, comprehensive analysis of causative and related genes should be of great importance not only for molecular diagnosis, but also for elucidating molecular epidemiology and dissecting molecular pathogenesis of ALS. With this background, we have constructed a high throughput gene analysis system and conducted comprehensive mutational analysis of ALS‐related genes.
Objectives: To develop a DNA microarray‐based high throughput resequencing system and to conduct comprehensive analysis of causative and related genes for familial and sporadic ALS patients.
Methods: We have developed a DNA microarray‐based high throughput resequencing system employing GeneChip Custom Resequencing System (Affymetrix). The microarray includes all the exon and flanking intron sequences of three causative genes (SOD1, ALS2 and DCTN1) and seven related genes (SLC1A2, SMN1, LIF, RNF19, ADAR2, CNTF and VEGF) for ALS. Forty‐two ALS patients, including seven familial and 35 sporadic cases were analysed. Genomic DNA samples were amplified using specific PCR primers, and processed according to the manufacturer's instructions. The handling of numerous PCR samples was accomplished by employing a robotics system to further enhance the throughput.
Results: We have completed resequencing of approximately 1 Mb (25 kb each for 43 patients), and identified five causative mutations. Two SOD1 mutations including one novel mutation and one previously identified mutation were found in seven familial cases. The patient with the novel mutation was characterized as late‐onset, slowly progressive ALS. Three mutations were identified in 35 apparently sporadic patients, which include one novel DCTN1 mutation and one previously known SOD1 mutation, and one SMN1 homozygous exon7 deletion mutation. Both the patient with the DCTN1 mutation and the patient with the SOD1 mutation presented typical ALS features with predominantly lower motor neuron involvement, clinically indistinguishable from other ALS patients. In addition, 27 single nucleotide substitutions were identified in the 10 genes. Among them, 11 substitutions (40%) were novel, including five non‐synonymous heterozygous substitutions in ALS2 in six sporadic ALS patients and one non‐synonymous single nucleotide substitution in VEGF in one atypical ALS patient.
Conclusions: Our approach for comprehensive analysis of causative and related genes has been proved to be fruitful for familial and sporadic ALS in identifying causative mutations and novel variations potentially associated with disease risks. The DNA microarray‐based resequencing system is highly useful for this approach, contributing not only to molecular diagnosis but also to molecular epidemiology and molecular dissection of ALS.