Prevalence of multiple sclerosis in Buenos Aires, Argentina using the capture-recapture method

Background:  Scarce data exist about multiple sclerosis (MS) prevalence in South America. The objective of the study is to determine the prevalence of MS in a high populated area from Argentina (Greater Buenos Aires Metropolitan area) using the capture-recapture methodology.
Methods:  Greater Buenos Aires is the generic denomination that refers to the megalopolis comprised by the autonomous city of Buenos Aires and the surrounding conurbation of the province of Buenos Aires. The study was carried out taking July 1996 as the prevalence month. We used capture-recapture method to estimate the prevalence of MS cross matching registries from four MS Centers.
Results:  A total of 803 registries were obtained from the four lists. Log-linear model for capture-recapture method was used to analyze the data. The population of the area based on the 1990 census was 12 594 974; the number of MS cases estimated amongst sources interactions were between 1833 and 2359; the prevalence estimated ranged from 14 to 19.8 cases per 100 000 inhabitants.
Conclusions:  This is the first study to provide epidemiological data on the prevalence of MS in a large population in Argentina (Greater Buenos Aires Metropolitan area). Further epidemiological studies will clarify the true prevalence of MS in South America.     

Incidence of multiple sclerosis in Buenos Aires: a 16‐year health maintenance organization‐based study

Objective: The present study was undertaken to determine the incidence of MS in a health maintenance organization from Buenos Aires, the largest populated area in Argentina. Methods: Population was all members of a hospital‐based health maintenance organization who were affiliated since January 1992 up to December 2007. Each person was followed contributing time at risk since January 1992 or enrollment date to the final date. Patients with definite diagnosis according to Poser’s criteria were included. Incidence density was calculated with 95% confidence intervals. Results: A total of 145 000 patients were followed for a total of 1 021 515 person‐years, of whom 18 developed the disease. Incidence density (ID): 1.76 /100 000 person‐years (95% CI: 1.1–2.8/100 000 person‐years). Conclusion: The incidence density of 1.76 per 100 000 suggests a low‐median risk area for MS. This study constitutes the first of its kind to cover data of MS incidence in Argentina.     

A systematic review of the epidemiology of multiple sclerosis in South America

Hundreds of publications dealing with the prevalence of multiple sclerosis (MS) throughout the world exist, but little data have been published from South America. Epidemiological studies of MS vary according to environmental, racial and genetic factors; a better understanding of MS in South America would help us to elucidate the disease pattern in this population. The aim of this study is to review the evidence relevant to MS epidemiology in South America. We performed a systematic review of articles of MS epidemiology in South America, with special emphasis on those providing information on the incidence and prevalence of MS (population‐based studies). Six papers provided information on MS epidemiology. One paper used the capture‐recapture methodology, while the remainder employed traditional methods to collect the data. Population‐based studies showed an MS prevalence rate ranging from 1.48 to 17 per 100 000 inhabitants. Available data suggest that the prevalence of MS is lower in South America than in developed countries. The reason for this observation is unknown. Some investigators suggest that certain environmental factors like sun exposure and vitamin D supplementation or the called ‘hygiene hypothesis’ may protect this population. Future studies will contribute to elucidate the etiology of that difference.     

Genetic and environmental factors and the distribution of multiple sclerosis in Europe

Background: The observation that the incidence of multiple sclerosis (MS) increases further from the equator has prompted considerable interest in the factors that might underlie this latitude gradient. Potential candidates include population frequencies of disease‐associated Human Leukocyte Antigen (HLA) alleles which are the major genetic component of MS susceptibility. Ultraviolet (UV) exposure and smoking have also been implicated as key environmental risk factors. Methods: We used multiple sources of published data on MS prevalence, HLA allele frequencies, UV index and cigarette smoking to assess the contributions of both nature and nurture to the distribution of MS within Europe. Results: We observed that HLA alleles unequivocally interact with a population‐wide level to determine disease risk. The UV index and smoking behaviour was also shown to correlate with disease distribution in Europe. For countries with HLA, UV and smoking data, these three factors were shown to account for 75% of the variance in MS prevalence. Conclusions: Genetic (HLA) and environmental (UV and smoking) risk factors thus interact in a complex manner with each other to determine a large proportion of MS susceptibility within Europe.     

Autoimmune diseases in families of French patients with multiple sclerosis

Multiple sclerosis (MS) is associated with autoimmune disorders (AIDs) in individual patients, and limited data suggest a possible familial association of MS and AIDs; however, no systematic study has been conducted on the occurrence of AIDs in the families of MS patients. Using a standardized interview focused on AIDs, we obtained the family histories of 357 consecutive patients from our MS clinic. Adequate information was obtained on 1971 first-degree relatives. Fifty-five patients (15.4%) had first-degree relatives with MS (n=22, 6.2%) another AID (n = 30, 8.4%), or both (n = 3, 0.8%). In 16 families (4.5%), at least 3 first-degree relatives had MS or another AID. MS, Grave's disease, rheumatoid arthritis, vitiligo, type 1 insulin-dependent diabetes mellitus, and uveitis, were the most common AIDs in these families. Such multiplex families (families with MS plus AID) are appropriate for identifying susceptibility genes that may be common to MS and other AIDs.     

Gender ratio trends over time in multiple sclerosis patients from Argentina

Several studies in multiple sclerosis (MS) suggest a trend of increasing disease frequency in women during the last decades. A direct comparison of gender ratio trends among MS populations from Argentina remains to be carried out. The objective of the study was to compare gender ratio trends, over a 50-year span in MS populations from Argentina. Methods: multicenter study that included patients from 14 MS Centers of Argentina. Patients with definite MS with birth years ranging from 1940 to 1989 were included. Gender ratios were calculated by five decades based on year of birth and were adjusted for the F/M born-alive ratio derived from the Argentinean national registry of births. The F/M ratios were calculated using a multivariate logistic regression per five decades by the year of birth approach. Analyses were performed using Stata 10.1. Results: 1069 patients were included. Gender ratios showed a significant increase from the first to the last decade in the whole MS sample (from 1.8 to 2.7; p value for trend = 0.023). The Gender ratio did not show differences considering MS subtype. Conclusion: our study showed a modest increase of the F/M ratio (from 1.8 to 2.7) over time among patients affected by MS in Argentina.     

The role of hereditary spastic paraplegia related genes in multiple sclerosis

Abstract Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system unsurpassed for its variability in disease outcome. It has been observed that axonal loss in MS is significant and that irreversible clinical disability relates to such axonal loss. The clinical similarities between Hereditary Spastic Paraplegia (HSP) and progressive MS, along with their analogous profiles of axonal loss in the long tracts, make the genes known to cause HSP biologically relevant candidates for the study of clinical outcome in MS. A cohort of sporadic MS cases and a set of unaffected controls were used to determine the role of HSP genes on MS susceptibility and disease severity. The MS cases were taken from opposite extremes of the putative distribution of long-term outcome using the most stringent clinical criteria to date. Genotyping the two sets of MS patients and controls could not provide any evidence to suggest that genes involved in the pathogenesis of HSP (Paraplegin, NIPA1, KIF5A, HSPD1, Atlastin, Spartin, Spastin, PLP1, L1CAM, Maspardin and BSCL2) play a role in susceptibility to, or modifying the course of, MS, although small effects of these genes cannot be ruled out.     

HLA-DRB1 and disease outcome in multiple sclerosis

The association between susceptibility to multiple sclerosis (MS) and the class II MHC allele HLA-DRB1*15 is well established although a possible relationship between this allele and outcome in MS is less clear. HLA-DRB1 typing was performed on 375 unrelated white patients with clinically definite MS and on 367 healthy controls. Putative associations of the gene with outcome were examined by dividing patients into two groups: those with an EDSS of 0-5.5 (mild/moderate disease) and those with an EDSS of 6-10 (severe disease). In order to minimise the effects of disease variability patients with a disease duration of at least 10 years or 15 years were examined. As subsidiary HLA-DRB1*03 and HLA-DRB1*04 associations have been previously reported, the effect of these alleles was also examined. As expected, HLA-DRB1*15 was found more frequently in patients than in controls (P < 0.000001). HLA-DRB1*15 positive patients had a significantly earlier age at onset than HLA-DRB1*15 negative patients. No significant associations were noted between HLA-DRB1*15 and outcome in the total patient group or in patients with a disease duration of 10 years or longer. In patients with a disease duration of at least 15 years HLA-DRB1*15 negative status was associated with a worse prognosis, although this did not remain significant after correction for multiple testing. It is thus likely that the contribution of HLA in MS is primarily towards onset and initial triggering mechanisms rather than influencing disease progression, chronicity and severity.     

Western and Asian features of multiple sclerosis in Mexican Mestizos

OBJECTIVES: The objective of this study was to compare the clinical expression of MS in Mexican Mestizos with that of patients of European or Asian descent; as well as to compare the annual frequency of new cases with that observed in the previous decades. PATIENTS AND METHODS: All patients with diagnosis of definite MS seen at the National Institute of Neurology and Neurosurgery of Mexico from January 1993 to December 2003 were studied (n=312). Sociodemographic and clinical characteristics were compared with reports of patients from either Western or Asian origin; the long-term disability score was analyzed according to gender, age of onset of MS and the initial symptom. RESULTS: The clinical expression of MS in Mexican Mestizos shares some characteristics with both, Asian and Western forms of MS indicating that the genetic composition of Mexican Mestizos participates in the clinical expression of the disease. Also, at the prevalence date, the mean age of patients and the duration of the disease were lower in our patients than in MS patients from endemic countries suggesting a true increasing incidence in recent times, rather than only improved case ascertainment. CONCLUSIONS: Clinical expression of MS in Mexican Mestizos shows the coexistence of some features common in European and in Asian cases.     

Effect of birthplace on the development of amyotrophic lateral sclerosis and multiple sclerosis

After World War II the southeastern part of Finland was ceded to the Soviet Union and its entire population evacuated to other areas of the country. The prevalences of amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS) were studied among the evacuees and compared to the corresponding data among the nonevacuated population. The prevalence of ALS among the war evacuees was two times higher than among the nonevacuated population (18.0 and 8.8 per 100,000, respectively). The prevalence of MS among the evacuees was only half of that found among the nonevacuated population, 38.3 and 73.0 per 100,000, respectively. The findings for ALS indicate that birthplace may have an effect on the later development of the disease and that there may have existed some environmental factor(s) which have made the evacuees more liable to contract the disease later in their lives. The low figure of MS for evacuees supports our previous results of an uneven geographic distribution of MS in Finland with the high-risk areas in the western and southwestern parts of the country. No accumulation of MS was found among the evacuees living in the high-risk areas.     

The genetic aspects of multiple sclerosis

The epidemiology of multiple sclerosis has been extensively investigated and two features have consistently emerged: marked geographical variation in prevalence and substantial familial clustering. At first sight, geographic variation would seem to imply an environmental cause for the disease, while familial clustering would seem to suggest that genetic factors have the predominant etiological effect. However, given that geographic variation in prevalence could result from variation in the frequency of genetic risk alleles and that familial clustering might result from shared environmental exposure rather than shared genetic risk alleles, it is clear that these crude inferences are unreliable. Epidemiologists have been resourceful in their attempts to resolve this apparent conflict between “nurture and nature” and have employed a whole variety of sophisticated methods to try and untangle the etiology of multiple sclerosis. The body of evidence that has emerged from these efforts has formed the foundation for decades of research seeking to identify relevant genes and this is the obvious place to start any consideration of the genetics of multiple sclerosis.     

An epidemiological study of multiple sclerosis in central Sardinia, Italy

Objectives – To verify morbidity estimates in central Sardinia, Italy. Methods – A prevalence study was performed in the province of Nuoro, Central Sardinia, which has a population of 273,768 inhabitants (135,383 men and 138,385 women). A complete enumeration approach was adopted by using all possible case-collection sources. Results – On prevalence day, December 31, 1993, 394 subjects (124 men and 270 women) living in the study area were known to suffer from definite and probable MS, giving a crude prevalence rate of 143.9 cases per 100,000 people, 91.6 for males and 195.11 for females. The crude prevalence estimated on December 31, 1985, based on 282 MS cases alive in the study area, was 102.94 per 100,000. Conclusion – This study reinforced central Sardinia's position as a high and rising prevalence area for MS.     

Analysis of 45 candidate genes for disease modifying activity in multiple sclerosis

Multiple sclerosis (MS) is a common inflammatory disease of the central nervous system unsurpassed for its variability in disease outcome. As little is conclusively known about MS disease mechanisms, we have selected a variety of candidate genes that may influence the prognosis of the disease based on their function. A cohort of sporadic MS cases, taken from opposite extremes of the putative distribution of long-term outcome using the most stringent clinical criteria to date, was used to determine the role of on MS disease severity. The MS cases selected represent the prognostic best 5 % (benign MS) and worst 5 % (malignant MS) of cases in terms of clinical outcome assessed by the EDSS. Genotyping the two sets of MS patients (112 benign and 51 malignant) and a replication cohort from Sardinia provided no evidence to suggest that the genes selected have any outcome modifying activity, although small effects of these genes cannot be ruled out.     

Peripheral neuropathy in multiple sclerosis: a clinical and electrophysiologic study

Peripheral nerve abnormalities are uncommon in multiple sclerosis (MS). When present, they are usually attributed to factors associated with advanced disease, such as malnutrition or cytotoxic drugs. We prospectively evaluated 22 mildly disabled MS patients with sensory complaints for evidence of neuropathy using the Neuropathy Symptom Score (NSS), clinical examination, and electrophysiologic studies of peripheral nerves. Distal latency, F-wave response, and nerve conduction velocity (NCV) and amplitude in the ulnar, median, tibial, peroneal and sural nerves were examined. Neuropathy was recorded if electrophysiologic abnormalities were detected in at least two peripheral nerves in the same patient. The most frequent electrophysiologic abnormalities noted were prolonged F-wave response and low motor amplitude in the peroneal nerve, slow sensory conduction velocities of the ulnar and sural nerves, and prolonged distal latencies in the sensory ulnar and sural nerves. Electrophysiologic abnormalities were found in 33 of 244 nerves examined (14.7%) and occurred in 10 patients (45.5%). Neuropathic symptoms were mild and did not correlate with electrophysiologic abnormalities. Age, disease duration, disease course and neurologic disability as evaluated by the Kurtzke Expanded Disability Status Scale, were not associated with the presence of neuropathy. Our findings indicate a high frequency of sensory-motor neuropathy in a selected group of MS patients.     

Epidemiology of multiple sclerosis in Bulgaria

An epidemiological study of MS in 5 districts of Bulgaria was carried out over period of 10 years to establish MS prevalence, incidence and mortality. The district of Sofia was the highest, indicating increased prevalence among the urban population, and more female than male cases. In the age group up to 15 years, age at onset was significantly earlier in the urban than in the rural cases.     

HLA-DRB1基因型与多发性硬化易患性的关系

目的：探讨HLA基因型与多发性硬化（MS）易患者的关系。以及临床表现与基因型的关系。方法：30例MS患者（包括2对双生子患者）、40名健康对照组，应用序列特异性引物聚合酶链反应（PCR－SSP）方法进行HLA－DRB1基因分型，对2个双生子家系进行家系分析。结果：单卵双生子？（经遗传标记确定）同患MS，病变均累及大脑，脑干和脊髓，基因型为HLA－DRB1＊09＊14．1。异卵双生子之一为复发缓解型视神经脊髓炎，基因型为DRB1＊01＊12，其未患病双生子妹妹为DRB1＊17＊12。根据病变部位。30例MS中视神经脊髓炎型和西方型各15个。脊髓（70．0％），和视神经（56．7％）是最常见病变累及部位。DR15的等位基因频率在MS组无显著增高，但DR12等位基因频率在MS中显著升高（10／30vs 4/40,P=0.0157)，分层分析显示视神经脊髓炎患者中DR12等位基因频率升高，差异有极显著意义（8／15vs 4/40,P=0.0019,RR=5.33)。结论：单卵双生子与异卵双生子的患病一致性差异表明，遗传因素在MS发病中起一定作用。DR12可能是部分视神经脊髓炎型MS的易患基因，关联基因的差异可能是东西方MS临床表现和病变部位不同的原因之一。     

Prevalence of multiple sclerosis in Belgrade, Yugoslavia

OBJECTIVES: To estimate the distribution of multiple sclerosis in the Belgrade population. METHODS: All persons who were affected and/or died from multiple sclerosis (Poser's criteria), with residence in the Belgrade region had been collected from January 1, 1985 to December 31, 1996. Prevalence was adjusted by direct method, using world population. RESULTS: From 1985 to 1996, 823 patients were suffering from multiple sclerosis. Sex ratio was 1:1.9. The mean age at onset was 32.2 +/- 9.8 years. A relapsing-remitting course of multiple sclerosis was reported in 50.7% patients, secondary progressive in 36.4%, patients, and primary progressive in 12.9% patients. On December 31, 1996, age-adjusted prevalence of multiple sclerosis in Belgrade was 41.5/100,000, 28.2/100,000 for males, and 54.1/100,000 for females. During the period studied, statistically highly significant increasing trend of multiple sclerosis prevalence was observed (P = 0.0001). CONCLUSIONS: According to findings presented in this study, Belgrade is an area with high prevalence of multiple sclerosis.