The association between ALS and population density: A population based study

Urbanization, air pollution, and water pollution: Identification of potential environmental risk factors associated with amyotrophic lateral sclerosis using systematic reviews

Introduction

Despite decades of research, causes of ALS remain unclear. To evaluate recent hypotheses of plausible environmental factors, the aim of this study was to synthesize and appraise literature on the potential associations between the surrounding environment, including urbanization, air pollution and water pollution, and ALS.

Methods

We conducted a series (n = 3) of systematic reviews in PubMed and Scopus to identify epidemiological studies assessing relationships between urbanization, air pollution and water pollution with the development of ALS.

Results

The combined search strategy led to the inclusion of 44 articles pertaining to at least one exposure of interest. Of the 25 included urbanization studies, four of nine studies on living in rural areas and three of seven studies on living in more highly urbanized/dense areas found positive associations to ALS. There were also three of five studies for exposure to electromagnetic fields and/or proximity to powerlines that found positive associations to ALS. Three case-control studies for each of diesel exhaust and nitrogen dioxide found positive associations with the development of ALS, with the latter showing a dose-response in one study. Three studies for each of high selenium content in drinking water and proximity to lakes prone to cyanobacterial blooms also found positive associations to ALS.

Conclusion

Whereas markers of air and water pollution appear as potential risk factors for ALS, results are mixed for the role of urbanization.

Airborne lead and polychlorinated biphenyls (PCBs) are associated with amyotrophic lateral sclerosis (ALS) risk in the U.S

Amyotrophic lateral sclerosis (ALS) risk is linked to environmental exposures. The National Emissions Inventory (NEI) database compiles mandatory reports of levels of airborne contaminants from a variety of stationary and mobile pollution sources across the U.S. The objective of this study was to identify airborne contaminants that may be associated with ALS etiology for future study. We geospatially estimated exposure to airborne contaminants as risk factors for ALS in a nationwide large de-identified medical claims database, the SYMPHONY Integrated Dataverse®. We extracted zip3 of residence at diagnosis of ~26,000 nationally distributed ALS patients and n = 3 non-ALS controls matched per case for age and sex. We individually aggregated the median levels of each of 268 airborne contaminants recorded in the NEI database for 2008 to estimate local residential exposure. We randomly broke the dataset into two independent groups to form independent discovery and validation cohorts. Contaminants associated with increased ALS risk in both the discovery and validation studies included airborne lead (false discovery rate (FDR) = 0.00077), and polychlorinated biphenyls (PCBs), such as heptachlorobiphenyl (FDR = 3.60E-05). Small aircraft were the largest source of airborne lead, while the PCB emissions came from certain power plants burning biomass, and from industrial boilers. Associations with residential history of lead exposure were confirmed in two additional cohorts (10 year top quartile in New Hampshire/Vermont OR 2.46 95% CI 1.46-2.80, and in Ohio OR 1.60 95% CI 1.28-1.98). The results of our geospatial analysis support neurotoxic airborne metals and PCBs as risk factors for ALS.

Is Population Density Associated with Non-Communicable Disease in Western Developed Countries? A Systematic Review

Over the last three decades, researchers have investigated population density and health outcomes at differing scale. There has not been a systematic review conducted in order to synthesise this evidence. Following the Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines, we systematically reviewed quantitative evidence published since 1990 on population density and non-communicable disease (NCD) within Westernised countries. Fifty-four studies met the inclusion criteria and were evaluated utilising a quality assessment tool for ecological studies. High population density appears to be associated with higher mortality rates of a range of cancers, cardiovascular disease and COPD, and a higher incidence of a range of cancers, asthma and club foot. In contrast, diabetes incidence was found to be associated with low population density. High and low population density are therefore risk markers for a range of NCDs, indicating that there are unidentified factors and mechanisms underlying aetiology. On closer examination, our synthesis revealed important and complex relationships between population density, the built environment, the nature of greenspace and man-made exposures. In light of increasing rates of morbidity and mortality, future research is required to investigate these associations in order to establish causative agents for each NCD.

Variation in worldwide incidence of amyotrophic lateral sclerosis: a meta-analysis

Background

To assess the worldwide variation of amyotrophic lateral sclerosis (ALS) incidence, we performed a systematic review and meta-analysis of population-based data published to date.

Methods

We reviewed Medline and Embase up to June 2015 and included all population-based studies of newly diagnosed ALS cases, using multiple sources for case ascertainment. ALS crude and standardized incidence (on age and sex using the US 2010 population) were calculated. Random effect meta-analysis and meta-regression were performed using the subcontinent as the main study level covariate. Sources of heterogeneity related to the characteristics of the study population and the study methodology were investigated.

Results

Among 3216 records, 44 studies were selected, covering 45 geographical areas in 11 sub-continents. A total of 13 146 ALS cases and 825 million person-years of follow-up (PYFU) were co-nsidered. The overall pooled worldwide crude ALS incidence was at 1.75 (1.55–1.96)/100 000 PYFU; 1.68 (1.50–1.85)/100 000 PYFU after standardization. Heterogeneity was identified in ALS standardized incidence between North Europe [1.89 (1.46–2.32)/100 000 PYFU] and East Asia [0.83 (0.42–1.24)/100 000 PYFU, China and Japan P = 0.001] or South Asia [0.73 (0.58–0.89)/100 000/PYFU Iran, P = 0.02]. Conversely, homogeneous rates have been reported in populations from Europe, North America and New Zealand [pooled ALS standardized incidence of 1.81 (1.66-1.97)/100 000 PYFU for those areas].

Conclusion

This review confirms a heterogeneous distribution worldwide of ALS, and sets the scene to sustain a collaborative study involving a wide international consortium to investigate the link between ancestry, environment and ALS incidence.

Epidemiology of Amyotrophic Lateral Sclerosis in the Republic of Cyprus: A 25-Year Retrospective Study

Introduction: Amyotrophic lateral sclerosis (ALS) is a rare, rapidly progressive neurodegenerative disease. Despite wide variability in the incidence and prevalence of ALS, there is evidence of positive temporal trends and an increase in incidence with age. The aim of this study was to conduct a detailed epidemiological investigation of ALS in Cyprus. Methods: All registered Cypriot ALS patients in the Republic of Cyprus from January 1985 until December 2014 were included. Socio-demographic information was extracted from patient files. Results: The study identified 179 ALS patients, of whom 7 had a positive family history. The mean age at onset was 58.6 years and a slight male predominance was observed. Average annual crude incidence was 1.26 cases/100,000 person-years and at the beginning of 2015, prevalence of ALS was 7.9 cases/100,000 population. Both incidence and prevalence displayed an increasing trend, even after age-standardization of incidence rates. Conclusions: Incidence, prevalence and main socio-demographic characteristics of ALS in Cyprus were similar to those of other European countries, without any geographic clustering of the disease. Additionally, an increased incidence through the years was confirmed. However, observations such as a higher male prevalence and a younger mean age of onset compared to published literature require further investigation.

Neurological deaths of American adults (55-74) and the over 75's by sex compared with 20 Western countries 1989-2010: Cause for concern

Background:

Have USA total neurological deaths (TNDs) of adults (55–74) and the over 75's risen more than in twenty Western Countries?

Methods:

World Health Organization TND data are compared with control mortalities cancer mortality rates (CMRs) and circulatory disease deaths (CDDs) between 1989–1991 and 2008–2010 and odds ratios (ORs) and confidence intervals calculated.

Results:

Neurological Deaths – Twenty country (TC) average 55–74 male rates per million (pm) rose 2% to 503 pm, USA increased by 82% to 627 pm. TC average females rose 1% to 390 pm, USA rising 48% to 560 pm. TC average over 75's male and female increased 117% and 143%; USA rising 368% and 663%, significantly more than 16 countries. Cancer mortality – Average 55–74 male and female fell 20% and 12%, USA down 36% and 18%. TC average over 75's male and female fell 13% and 15%, the USA 29% and 2%. Circulatory deaths – TC average 55–74 rates fell 60% and 46% the USA down 54% and 53%. Over 75's average down 46% and 39%, USA falling 40% and 33%. ORs for rose substantially in every country. TC average 75's ORs for CMR: TND male and females were 1:2.83 and 1:3.04 but the USA 1:5.18 and 1:6.50. The ORs for CDD: TND male and females TC average was 1:3.42 and 1:3.62 but the USA 1:6.13 and 1:9.89.

Conclusions:

Every country's neurological deaths rose relative to the controls, especially in the USA, which is a cause for concern and suggests possible environmental influences.

Space-time distribution of the ALS incident cases by onset type in the Health District of Ferrara, Italy

OBJECTIVES

An ecological study in the resident population of the Health District (HD) of Ferrara, Italy, has been carried out to establish the distribution in space and time of the amyotrophic lateral sclerosis (ALS) incident cases according to the disease onset type and gender in the period 1964-2009.

MATERIAL AND METHODS

The hypothesis of a uniform distribution was assumed.

RESULTS

The incident cases of spinal onset ALS and bulbar onset ALS were evenly distributed in space and time in both men and women. The spinal onset ALS incident cases distribution according to gender was significantly different from the expected in the extra-urban population (20 observed cases in men 95% Poisson confidence interval 12.22-30.89, expected cases in men 12.19; six observed cases in women 95% Poisson confidence interval 2.20-13.06, expected cases in women 13.81), whereas no difference was found in the urban population. The spinal onset ALS incidence was higher in men than in women in the extra-urban population (difference between the rates = 1.53, 95% CI associated with the difference 0.52-2.54), whereas no difference between sexes was found in the urban population.

CONCLUSIONS

The uneven distribution according to gender of the spinal onset ALS incident cases only in the extra-urban population suggests the involvement of a gender related environmental risk factor associated with the extra-urban environment. Despite some limits of the spatial analysis in the study of rare diseases, the results appear consistent with the literature data.

Record linkage between hospital discharges and mortality registries for motor neuron disease case ascertainment for the Spanish National Rare Diseases Registry

Our objective was to analyse the coverage of hospital discharge data and the mortality registry (MR) of La Rioja to ascertain motor neuron disease (MND) cases to be included in the Spanish National Rare Diseases Registry. MND cases that occurred in La Rioja during the period 1996-2011 were selected from hospital discharge data and the MR by means of the International Classification of Diseases. Review of the medical histories was carried out to confirm the causes of death reported. Characteristics of the population with MND were analysed. A total of 133 patients with MND were detected in La Rioja during the period 1996-2011; 30.1% were only recorded in the hospital discharges data, 12.0% only in the MR, and 57.9% were recorded by both databases. Medical records revealed a miscoding of patients who had been diagnosed with progressive supranuclear palsy but were recorded in the MR with an MND code. In conclusion, the hospital discharges data and the MR appear to be complementary and are valuable databases for the Spanish National Rare Diseases Registry when MNDs are properly codified. Nevertheless, it would be advisable to corroborate the validity of the MR as data source since the miscoding of progressive supranuclear palsy has been corrected.

Incidence of amyotrophic lateral sclerosis in Rhineland-Palatinate, Germany

There is a lack of prospective and population based epidemiological data on amyotrophic lateral sclerosis in Germany to date. The ALS registry Rhineland-Palatinate was established to investigate the incidence, course and phenotypic variety of ALS in this south-west German state of about 4 million inhabitants. During the period 2010-2011, consecutive incident patients with amyotrophic lateral sclerosis according to the revised El Escorial criteria were included and followed up using multiple overlapping sources of case ascertainment. One hundred and forty-six patients were enrolled. The annual crude incidence for amyotrophic lateral sclerosis in Rhineland-Palatinate was 1.8/100,000 person-years (95% CI 1.6-2.2). Male to female ratio was 1.1:1. Incidence increased with age reaching a peak in the 70-74 years age group and declined thereafter. Late-onset ALS (≥ 75 years) was found in 14.4% of patients. About 32% of patients presented with bulbar onset. In conclusion, incidence rate of amyotrophic lateral sclerosis in Rhineland-Palatinate is within the range of other prospective population based registers in Europe and North America. Gender ratio is nearly balanced.

Review: the role of vitamin D in nervous system health and disease

Vitamin D and its metabolites have pleomorphic roles in both nervous system health and disease. Animal models have been paramount in contributing to our knowledge and understanding of the consequences of vitamin D deficiency on brain development and its implications for adult psychiatric and neurological diseases. The conflation of in vitro, ex vivo, and animal model data provide compelling evidence that vitamin D has a crucial role in proliferation, differentiation, neurotrophism, neuroprotection, neurotransmission, and neuroplasticity. Vitamin D exerts its biological function not only by influencing cellular processes directly, but also by influencing gene expression through vitamin D response elements. This review highlights the epidemiological, neuropathological, experimental and molecular genetic evidence implicating vitamin D as a candidate in influencing susceptibility to a number of psychiatric and neurological diseases. The strength of evidence varies for schizophrenia, autism, Parkinson's disease, amyotrophic lateral sclerosis, Alzheimer's disease, and is especially strong for multiple sclerosis.

Epidemiology of amyotrophic lateral sclerosis in Emilia Romagna Region (Italy): A population based study

Our objective was to describe incidence and clinical features of ALS from a prospective population-based study in Emilia Romagna Region (ERR). From 2009 onwards, a prospective registry recorded all incident cases of ALS among residents in the ERR (population, 4.4 million inhabitants), involving 17 neurological departments. For each patient, detailed demographic and clinical information was collected by caring physicians. Results showed that from 1 January 2009 to 31 December 2011, 347 patients received a new diagnosis of ALS with a crude incidence rate of 2.63/100,000/year. There was micro-geographic heterogeneity throughout ERR, with higher incidence rates in the low density population (3.27/100,000) (p < 0.01). ALS patients have been more frequently employed in agriculture than the general ERR population (8.64% vs. 4.6%, p < 0.01). Clinical features were similar to those described in previous population based studies. In conclusion, we report incidence rates similar to those reported by European registries, reflecting good accuracy of our prospective study. We confirmed previous studies reporting higher incidence rates in rural areas and among agricultural workers. Although genetics has been gaining increasing importance in ALS aetiology, some epidemiological data are still unexplained. Identifying geographical areas or populations with high incidence rates can be a starting point for identifying environmental risk factors. Further studies having this specific aim can shed light on these topics.

Different occupations associated with amyotrophic lateral sclerosis: is diesel exhaust the link?

The cause of sporadic amyotrophic lateral sclerosis (SALS) remains unknown. We attempted to find out if occupational exposure to toxicants plays a part in the pathogenesis of this disease. In an Australia-wide case-control study we compared the lifetime occupations of 611 SALS and 775 control individuals. Occupations were coded using country-specific as well as international classifications. The risk of SALS for each occupation was calculated with odds ratios using logistic regression. In addition, the literature was searched for possible toxicant links between our findings and previously-reported occupational associations with SALS. Male occupations in our study that required lower skills and tasks tended to have increased risks of SALS, and conversely, those occupations that required higher skills and tasks had decreased risks of SALS. Of all the occupations, only truck drivers, where exposure to diesel exhaust is common, maintained an increased risk of SALS throughout all occupational groups. Another large case-control study has also found truck drivers to be at risk of SALS, and almost two-thirds of occupations, as well as military duties, that have previously been associated with SALS have potential exposure to diesel exhaust. In conclusion, two of the largest case-control studies of SALS have now found that truck drivers have an increased risk of SALS. Since exposure to diesel exhaust is common in truck drivers, as well as in other occupations that have been linked to SALS, exposure to this toxicant may underlie some of the occupations that are associated with SALS.

Global epidemiology of amyotrophic lateral sclerosis: a systematic review of the published literature

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is relatively rare, yet the economic and social burden is substantial. Having accurate incidence and prevalence estimates would facilitate efficient allocation of healthcare resources.

OBJECTIVE

To provide a comprehensive and critical review of the epidemiological literature on ALS.

METHODS

MEDLINE and EMBASE (1995-2011) databases of population-based studies on ALS incidence and prevalence reporting quantitative data were analyzed. Data extracted included study location and time, design and data sources, case ascertainment methods and incidence and/or prevalence rates. Medians and interquartile ranges (IQRs) were calculated, and ALS case estimates were derived using 2010 population estimates.

RESULTS

In all, 37 articles met the inclusion criteria. In Europe, the median incidence rate (/100,000 population) was 2.08 (IQR 1.47-2.43), corresponding to an estimated 15,355 (10,852-17,938) cases. Median prevalence (/100,000 population) was 5.40 (IQR 4.06-7.89), or 39,863 (29,971-58,244) prevalent cases.

CONCLUSIONS

Disparity in rates among ALS incidence and prevalence studies may be due to differences in study design or true variations in population demographics such as age and geography, including environmental factors and genetic predisposition. Additional large-scale studies that use standardized case ascertainment methods are needed to more accurately assess the true global burden of ALS.

pNfH is a promising biomarker for ALS

A diagnostic biomarker for ALS would permit early intervention with disease-modifying therapies while a biomarker for disease activity could accelerate the pace of drug discovery by facilitating shorter, and less costly, drug trials to be conducted with a smaller number of patients. Neurofilaments are the most abundant neuronal cytoskeletal protein. We set out to determine whether pNfH was a credible biomarker for ALS. pNfH levels were determined using an ELISA for 150 ALS subjects and 140 controls. We demonstrated a seven-fold elevation in the cerebrospinal fluid (CSF) levels of phosphorylated neurofilament heavy subunit (pNfH) in ALS (median = 2787 pg/ml, n = 150), compared to headache and other benign controls (394 pg/ml, n = 100, p = < 0.05). There was a 10-fold elevation of pNfH compared to ALS mimics (266 pg/ml, n = 20) and other neurodegenerative and inflammatory conditions (279 pg/ml for n = 20) which was also highly significant (p = < 0.05). pNfH achieved a diagnostic sensitivity of 90% and specificity of 87% in distinguishing ALS from all controls. We also detected an inverse correlation between CSF pNfH levels and disease duration (time from symptom onset to death, r(2 = )0.1247, p = 0.001). In conclusion, pNfH represents a promising candidate for inclusion in a panel of diagnostic and prognostic biomarkers.

Amyotrophic lateral sclerosis in Sardinia, insular Italy, 1995-2009

Recent genetic studies suggest a Sardinian type of amyotrophic lateral sclerosis (ALS). Thus, ALS incidence, prevalence and survival were investigated in a large population of Sardinians aimed to disclose population-specific patterns and their temporal changes. This is a population-based incidence and prevalence study in northern and central Sardinia, insular Italy (over 700,000 population). Incidence rates were computed for the time interval 1995-2009 and by quinquennia. Prevalence was computed for prevalence days 31 December 2004 and 2009. Onset-based survival for 1995-2009 is also reported. All ALS patients (El Escorial Criteria) in the study area were retrospectively included. The ALS crude incidence from 2005-2009 was 2.5 (95 % CIs: 0.1, 4.9), 3.4 in men and 1.6 in women. Onset occurred most often between the age of 65-74 years in men and 55-64 years in women. The ALS incidence tended to increase over the period 1995-2009. The mean age at onset was 61.7 years with no difference based on gender, varying significantly from 59.9 years in 1995-1999 to 63.9 years in 2005-2009. On December 31, 2009, the ALS crude prevalence was 10.8 per 100,000 (95 % CIs: 8.6, 13.1), 13.8 in men and 8.0 in women, whereas it was 6.3 per 100,000 (95 % CIs: 4.1, 8.6) on December 31, 2004 (M:F ratio of 0.95). Mean survival from onset was 37.0 months, with no difference based on gender, and a tendency to decrease during the period 1995-2009, in relation to type and age of onset. The population-based incidence and prevalence data of ALS in Sardinians indicate an increase of the disease occurrence over the past 40 years, providing support for a population-specific variant of ALS in Sardinia.