Motor neuron disease in the Province of Turin, Italy, 1971-1980

Geographical clusters of amyotrophic lateral sclerosis and the Bradford Hill criteria

With the aim of shedding further light on the role of environmental factors in amyotrophic lateral sclerosis (ALS) etiology, we hereby conducted a historical narrative review to critically appraise the published reports on ALS geographical clusters using the modern interpretation of the Bradford Hill criteria for causation. Our research hypothesis was that the more criteria were met, the greater was the evidence supporting a causal association. We found that cluster studies that met the greatest number of Bradford's Hill criteria regarded the non-protein amino acid β-N-methylamino-L-alanine (L-BMAA) and exposure to metals and minerals, but the evidence for causation was at best moderate and was poor for other environmental factors. This defective picture might be attributed not only to the methodological approach adopted by published studies, but also to the inherent difficulties in the application of Bradford Hill criteria, due to the complexity of the disease phenotype and the underlying pathogenic mechanisms.

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.

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.

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.

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.

High frequency of the expanded C9ORF72 hexanucleotide repeat in familial and sporadic Greek ALS patients

An intronic expansion of a hexanucleotide GGGGCC repeat in the C9ORF72 gene has recently been shown to be an important cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) in familial and sporadic cases. The frequency has only been defined in a small number of populations where the highest sporadic rate was identified in Finland (21.1%) and the lowest in mainland Italy (4.1%). We examined the C9ORF72 expansion in a series of 146 Greek ALS cases, 10.95% (n = 16) of cases carried the pathological expansion defined as greater than 30 repeats. In the 10 familial ALS probands, 50% (n = 5) of them carried a pathologically large expansion. In the remaining 136 sporadic ALS cases, 11 were carriers (8.2%). None of the 228 Greek controls carried an expanded repeat. The phenotype of our cases was spinal (13/16) or bulbar (3/16) ALS, the familial cases were all spinal ALS and none of our cases had behavioral frontotemporal dementia. Expansions in the C9ORF72 gene therefore represent a common cause of ALS in Greece and this test will be diagnostically very important to implement in the Greek population. The frequency is higher than other populations with the exception of Finland and this may be due to Greece being a relatively isolated population.

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

We aimed to assess whether rural residence is associated with amyotrophic lateral sclerosis in the south-east of England using a population based register. Previous studies in different populations have produced contradictory findings. Residence defined by London borough or non-metropolitan district at time of diagnosis was recorded for each incident case in the South-East England ALS Register between 1995 and 2005. Each of the 26 boroughs or districts of the catchment area of the register was classified according to population density. Age- and sex-adjusted incidence of ALS was calculated for each region and the relationship with population density tested by linear regression, thereby controlling for the underlying population structure. We found that population density in region of residence at diagnosis explained 25% of the variance in ALS rates (r = 0.5, p < 0.01). Thus, in this cohort in the south-east of England, people with ALS were more likely to be resident in areas of high population density at diagnosis.

Ethnic variation in the incidence of ALS: a systematic review

BACKGROUND

The findings of recent genetic polymorphism studies in ALS suggest that the influence of genetic risk factors for the disease may vary by ethnicity. It is now widely accepted that the incidence of ALS is uniform across Caucasian populations, but whether racial variation across other ethnicities exists remains unknown.

METHOD

Systematic review of the known literature on the incidence, prevalence, and mortality of ALS across all ethnicities. To facilitate comparison, studies were grouped according to the type of data presented and examined for sources of case ascertainment and inclusion criteria.

RESULTS

The literature search identified 61 publications. Lower standardized incidence rates were observed in Asian than Caucasian populations. Within the United States, several incidence and mortality studies have identified lower ALS frequency among African American and Hispanic populations than among non-Hispanic Caucasians. These observations are supported by the other data sources.

CONCLUSIONS

The incidence of ALS may be lower among African, Asian, and Hispanic ethnicities than among whites. We conclude with proposals for a prospective epidemiologic study concentrating on non-Caucasian populations.

Epidemiology of motor neuron disease in the Kii Peninsula of Japan, 1989-1993: active or disappearing focus?

During the period 1989-1993, the incidence and migration patterns of patients with motor neuron diseases (MND) in Wakayama Prefecture, including one of the high-incidence Kii Peninsula foci ('Kozagawa focus'), were surveyed to determine whether the focus had truly disappeared or not. Overall, the crude average annual incidence was 1.43 per 100000 population; when age-adjusted to the 1990 Japanese population, it was 1.25 (1.85 for males and 0.61 for females). The average annual age- and sex-specific incidence steadily increased to a peak between 60 and 69 years and dropped after 70. Geographically, the rates varied in the five regions of Wakayama Prefecture from 0.38 to 2.48. The areas with high incidence were distributed in the central and southernmost regions; the highest was in the Kozagawa focus with 9.54 (two ALS cases within five years; 4193 base population, 1990). During the study period, four emigrants from Kozagawa had developed MND one to four decades after leaving the focus. Although the remarkable clustering of MND was thought to have disappeared, the southern Kii Peninsula remains a high-risk area for MND, especially if one interprets the data so as to include the emigrants. In general, the age at onset has increased in the past 20 years from 56.5 to 61.7; male predominance is observed.

Clinical epidemiology of amyotrophic lateral sclerosis

The introduction of palliative therapies in amyotrophic lateral sclerosis (ALS) will alter the epidemiology of ALS as it is known now. Although incidence rates will remain unchanged in the near future, prevalence rates will likely increase dramatically. Better understanding of the age-specific presentation of motor neuron diseases worldwide will shed light on the vexing questions concerning the variable incidence rates in some countries and apparent incidence gradients in North America and Europe.

Steadiness of amyotrophic lateral sclerosis in the province of Parma, Italy, 1960-1990

A clinical and epidemiological study on amyotrophic lateral sclerosis (ALS) was conducted in the province of Parma, Italy, from 1960-1990. A total of 121 cases were collected from hospital records. The average annual incidence was 0.98 per 100,000 inhabitants, with a male/female ratio of 1.1. Age-specific incidence was maximal in the age group 60-69 years. No difference between rural and urban areas was found. Prevalence on October 26th, 1981 was 2.5 per 100,000. Mean age at onset was 60 years, with no significant sex difference. Mean duration of the disease was 30 (sd 21.4) months. Bulbar forms were significantly (p < 0.05) shorter than conventional forms, with a mean duration of 23.4 (sd 21.4) months. Age at onset did not influence prognosis. A comparison of three decades was made, to verify whether possible variations of the disease had occurred with time. From our data a definite stability was found in such epidemiological parameters as incidence, prevalence, mean duration and mortality of ALS in the period.

Rising mortality from motor neurone disease in Sweden 1961-1990: the relative role of increased population life expectancy and environmental factors

Recent studies of mortality from motor neurone disease (MND) in Sweden have demonstrated rising levels of mortality from the disease, especially amongst older age groups. Case-control investigations have suggested that certain environmental factors are significantly related to variations in mortality from the disease, and are associated with a probable individual susceptibility to MND. This study applies an innovative epidemiological technique to longitudinal and cohort analysis of Swedish mortality from MND during the period 1961 to 1990. Survival modelling shows that a subpopulation susceptible to MND exists in Sweden, as has been demonstrated in other countries. The increased life expectancy of the Swedish population since 1961 has resulted in more of that susceptible population living to the ages at which MND is expressed, explaining the majority of the increase in mortality from the disease. However, environmental factors may play a role in accelerating the course of MND and may affect the timing of death within the susceptible sub-population.

Amyotrophic lateral sclerosis in Sardinia, Italy: an epidemiologic study

The authors carried out an epidemiologic study on amyotrophic lateral sclerosis in Sardinia for the years 1957 through 1990. The duration of the disease and survival were significantly shorter in bulbar form. The distribution of ALS in various areas of the island was found to be not at all homogeneous. Mean yearly incidence showed no significant variations in the decades 1971-80 and 1981-90. In the last decade, an increase of bulbar forms was observed.

Adult onset motor neuron disease: worldwide mortality, incidence and distribution since 1950

This review examines the commonly held premise that, apart from the Western Pacific forms, motor neuron disease (MND), has a uniform worldwide distribution in space and time; the methodological problems in studies of MND incidence; and directions for future epidemiological research. MND is more common in men at all ages. Age-specific incidence rises steeply into the seventh decade but the incidence in the very elderly is uncertain. A rise in mortality from MND over recent decades has been demonstrated wherever this has been examined and may be real rather than due to improved case ascertainment. Comparison of incidence studies in different places is complicated by non-standardised methods of case ascertainment and diagnosis but there appear to be differences between well studied populations. In developed countries in the northern hemisphere there is a weak positive correlation between standardised, age-specific incidence and distance from the equator. There is now strong evidence for an environmental factor as the cause of the Western Pacific forms of MND. A number of clusters of sporadic MND have been reported from developed countries, but no single agent identified as responsible.

Amyotrophic lateral sclerosis in Sweden in relation to occupation

All cases of ALS in Sweden during the period 1970-1983, i.e., 1961 cases, were compared with an age-stratified random sample of 2245 individuals from the Swedish population. On the basis of census information, the male cases were found to be heterogeneously distributed over occupational groups. Significantly more male cases than expected were found among office workers (OR = 1.8; 34 cases) as well as among farm workers (OR = 1.7; 56 cases). There was a cluster of male cases in agricultural work in one south-western county (OR = 3.4; 25 cases). Significantly more female cases than expected were medical service workers (OR = 1.7; 33 cases).

Epidemiology of amyotrophic lateral sclerosis in Hordaland county, western Norway

The incidence, prevalence and prognosis of amyotrophic lateral sclerosis (ALS) in the county of Hordaland, western Norway were determined for the years 1978 through 1988. The average annual incidence rate was 1.60 per 100,000 population with a male to female ratio of 1.26 (95% confidence interval: 0.76-2.09). The maximal age-specific annual incidence was 8.12 per 100,000 and occurred in the age-group between 61 and 65 years. The prevalence of ALS was 3.67 per 100,000 on December 31, 1988. The average age at the onset of the disease was 60.9 years ranging from 34 to 82 years of age. Survival was studied with life table techniques. Median survival from the onset of symptoms was 28.0 months overall. In patients with bulbar onset the median survival was 24.0 months whereas it was 40 months in patients with spinal onset of disease (log rank test, P = 0.0004). The difference in survival between ALS with bulbar or spinal onset was not explained by age or sex differences in the two groups.

Population frequencies of neuromuscular diseases--II. Amyotrophic lateral sclerosis (motor neurone disease)

A summary of the world literature on the prevalence of amyotrophic lateral sclerosis (motor neurone disease) has been carried out. Excluding those particular isolates with especially high prevalences (e.g. Guam and the Kii Peninsula of Japan), the mean prevalence among both sexes in other populations is around 41.6 x 10(-6) or 1 in 24,000.

Motor neuron disease (amyotrophic lateral sclerosis)

Amyotrophic lateral sclerosis is an insidiously developing, adult-onset, progressive anterior horn cell degeneration with associated degeneration of descending motor pathways. It has been recognized as an important clinical syndrome since the middle of the 19th century. Despite increasing clinical and research interest in this condition, its cause remains obscure, even in the broadest terms. Epidemiologic characteristics of the disease have been interpreted as evidence of both genetic and environmental causes. A major change in the view of this disease is the widely developing perception that it is a disease of elderly persons more than of middle-aged adults as was previously taught. Etiologic hypotheses encompass a broad range of postulated pathophysiologic mechanisms, and we review these in detail. The clinical limits of the disease can now be better defined by using modern diagnostic techniques. Although interest in supportive symptomatic therapy is growing, no intervention has yet been shown to modify the biologically determined motor system degeneration.

Amyotrophic lateral sclerosis in Palermo, Italy: an epidemiological study

The incidence, prevalence and natural course of ALS were determined in the population of the province of Palmero, Italy. The average annual incidence calculated for the years 1973 through 1984, was 044./100.000 inhabitants. The prevalence rate on prevalence day December 31, 1984, was 1.67/100.000 population. The male/female ratio was 1.38. The mean age at onset was 54.3 +/- 11.02. The most common clinical form was the conventional one (61.4%); the bulbar form was more frequent among females than males. The mean duration of the disease was 33.7 +/- 35.8 months. The longest duration belongs to the pseudopolyneuritic form. The median survival was 36 months: 16 months for the bulbar, 36 months for the conventional and 51 months for the pseudopolyneuritic form.

Epidemiology of amyotrophic lateral sclerosis in the province of Modena, Italy. Influence of environmental exposure to lead

A retrospective study of all admissions to the University of Modena Neurological Department from 1976-1986; 51 cases of amyotrophic lateral sclerosis (ALS) were found. ALS mean annual incidence was 0.78/100,000 inhabitants, while prevalence was 2.35/100,000. Mean age at onset was 61.43 years, mean and median duration of illness were, respectively, 28.83 and 24.5 months, and survival at 5 years post-onset was 24.4%. A tendency to higher incidence and prevalence of ALS in the ceramic district, when compared with those of the rest of the province was found. However, the small number of cases did not allow any conclusive statistical correlation between environmental exposure to lead and frequency of ALS.

Motor neuron disease in Cantabria

Sixty-two patients with motor neuron disease (MND), encompassing amyotrophic lateral sclerosis (ALS), progressive bulbar palsy (PBP) and progressive muscular atrophy (PMA), were selected from within a defined area (Cantabria) in northern Spain, from 1974 to 1985. The annual incidence of MND was 1.01 per 100,000 inhabitants and the prevalence rate was 3.52 per 100,000. The male to female ratio was 1.78:1. Age-specific incidence rates increased with advanced age, with a maximum between 60 and 69 years for males and over 70 years for females. The median age at onset was 60.5 years. The average interval between the onset symptoms and diagnosis was 11 months. Fifty-three per cent of the patients had conventional or pseudopolyneuritic ALS, 36% had PBP and 11% had PMA. There were three familial cases. Two PMA patients had had acute poliomyelitis. The mean duration of the disease was 26.6 months and was significantly longer in males aged under 60 years. The survival rates in 50 patients with adequate follow-up were 18% after 5 years from onset and 6% after 10 years.

A survival analysis of 155 cases of progressive muscular atrophy

We performed a survival analysis of 155 cases of progressive muscular atrophy (PMA). In about half the cases, hands were involved first, the lower limbs in 30% and the shoulder girdle in 23%. The lifetables of PMA, adjusted to the expected mortality, showed a survival rate of 61.3% and 56.4% at three and five years, respectively. The location of onset symptoms did not modify the life expectancy, whereas the age of the patients at the moment of first diagnosis had a great influence on the course of the disease. The patients were further subdivided in two groups on the basis of the diffusion of the neuromuscular damage at the moment of the diagnosis. The course of the patients with a localized disease was markedly better than that of subjects with widespread disease. Some hypotheses are made about the latter group of cases.

Motor neuron disease in the province of Turin, Italy, 1966-1980. Survival analysis in an unselected population

We performed a population based survival analysis of all incident cases (220) of motor neuron disease (MND) in the province of Turin, Italy, during the period 1966-1980. 175 cases were diagnosed as amyotrophic lateral sclerosis (ALS), 43 as progressive muscular atrophy (PMA) and 2 as progressive bulbar palsy (PBP). The life-tables of MND, adjusted as to the "expected" mortality, showed a survival rate of 27.8% and 22.0% at 5 and 10 years, respectively. The course of PMA and ALS cases was different, with a 5-year survival rate of 66.8% and 17.7%, respectively. Nevertheless both life-tables showed a similar pattern with a rapidly fatal outcome in the first 3 years after diagnosis and a slower death rate in the following years. In each curve, the slopes suggested the presence of 2 subgroups with different prognosis. It is to be stressed that a percentage of PMA patients (25.7%) showed a rapidly fatal outcome and that a subgroup of ALS patients (26.6%) showed a relatively benign course. This might suggest a different individual susceptibility to the disease.