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.     

Migration and age at onset of multiple sclerosis: some pitfalls of migrant studies

The aim of this study was to compare age at onset of multiple sclerosis (MS) in North African-born and French-born patients. The migrant group consisted of 246 patients who arrived in France during the period 1960-1965. Among these migrants, 27 (11%) had first symptoms before migration. The French-born group consisted of MS patients of same sex and age at the time of the study as migrants who were randomly selected from a large national sample. After controlling for various biases which could explain differences between migrants and French-born patients, we found no differences in mean age at MS onset between the two groups. Therefore, it is likely that MS was acquired by the same age in migrants as in French-born patients. This finding may constitute an indirect support for the hypothesis that the unknown causative factors of MS are equally frequent whatever the latitude of origin.     

Anticipation of age at onset in familial multiple sclerosis

Background and objective: Anticipation of age at onset in the younger generations is a widely known characteristic of many diseases with genetic inheritance. This study was performed to assess whether there is anticipation of age at onset in younger generations of familial multiple sclerosis (MS) in a Spanish population and to compare clinical characteristics of familial and sporadic MS. Methods: We studied a cohort of 1110 patients diagnosed with MS and followed‐up in our MS Unit. Patients were considered as familial MS if they had in their family at least one relative of first or second degree diagnosed with MS. Otherwise, patients were considered to have sporadic MS. We compared the age at onset between relatives from different generations, and we also compared the age at onset of familial and sporadic MS. Results: A lower age at onset in the younger generations was found (median 22 years vs. 30 years, P < 0.001) and a significant lower age at onset of the disease in familial MS comparing to sporadic MS (median 25 years vs. 29 years, P = 0.042). Conclusions: There is an anticipation of the age at onset of MS in the younger generations of patients with familial MS. There is also a lower age at onset in familial versus sporadic MS.     

Anticipation of age at onset in multiple sclerosis: methodologic pitfalls

Alonso‐Magdalena L, Romero‐Pinel L, Moral E, Carmona O, Gubieras L, Ramón JM, Martínez‐Yélamos S, Arbizu T. Anticipation of age at onset in multiple sclerosis: methodologic pitfalls.
Acta Neurol Scand: 2010: 121: 426–428.
© 2010 John Wiley & Sons A/S. Background/aim – There are several reports that claim anticipation in complex or polygenic diseases such as multiple sclerosis (MS), Crohn disease or schizophrenia. The aim of the present study was to assess age at onset of MS during the last 60 years in the region of Costa de Ponent (Barcelona, Spain) showing how apparent changes in age at onset between generations can be an artefact of analysis based on cohorts that have not been followed enough time. Methods – The study comprised 1100 patients diagnosed of MS. The method used to correct for follow‐up time bias involves constructing comparison cohorts that had been observed for the same amount of time. To ensure equal follow‐up times, we restricted our analysis to patients whose onset was by 37 years of age (percentile 75) and were at least 37 years old. We analysed differences in age at onset using log‐rank test to compare survival curves estimated by Kaplan–Meier method. Results – Age at onset decreases progressively from older to younger generations. However, when adjustment to equal follow‐up time was done, anticipation in age at onset was not found. Conclusion – Anticipation of age at onset is undetectable when adjusted for follow‐up time.     

Geographic distribution of multiple sclerosis: An update with special reference to Europe and the Mediterranean region

The geographic distribution of multiple sclerosis (MS) was last reassessed in 1975 with data from 180 surveys from about the world. Since then there have been an additional 54 for which prevalence rates have been measured or estimated. In broad terms the world-wide distribution of MS still seems best described as comprising three bands or zones of high, medium, and low frequency or risk. For the entire 35 years since World War II, prevalence rates of 30 or more per 100,000 population have defined high frequency, those of 5–29 medium frequency, and those of less than 5 per 100,000 low frequency.
High frequency areas are northern and central Europe into the USSR; southern Canada and northern United States; and New Zealand and southern Australia. These regions are bounded by medium frequency areas, which include southern US; southwestern Norway and northern Scandinavia; probably the USSR from the Ural Mountains into Siberia as well as the Ukraine; and the entire Mediterranean basin from Spain around to Israel – possibly including Tunisia. Enna in Sicily with a high rate is an exception. Also of medium frequency are most of Australia and perhaps the mid-portion of South America. One white group of South Africa too has a medium prevalence rate. Low frequency areas include all known parts of Asia and Africa (save as noted above); the Caribbean region to include Mexico, and probably northern South America; and Alaska and Greenland.
The high to medium division in southern Europe extends eastward in an irregularly curved line from about 43° north latitude in the west to some 49°–50° north latitude within the USSR west of the Urals. From a large nationwide case-control series, the division between high and medium in the US is at 37° north latitude across most of the country but extending to some 39° in the east.     

Clinical differences in patients with unilateral hippocampal sclerosis and unitemporal or bitemporal epileptiform discharges

PURPOSE: To investigate factors determining the presence of bilateral interictal epileptiform discharges (IEDs) in temporal lobe epilepsy (TLE) with unilateral hippocampal sclerosis (HS). METHODS: We analysed data of 243 TLE patients with unilateral HS who had long-term video-EEG. Eighty-one patients (33%) had bitemporal IEDs. RESULTS: We categorised patients into a unilateral group (UG), a bilateral group (BG) according to presence of bitemporal IEDs. We found no difference between UG and BG regarding epilepsy duration, secondarily generalised seizures, and history of febrile seizures. Mean seizure frequency was significantly higher in the BG (UG: 7.7+/-14.7 seizures/month; BG: 13+/-35 seizures/month, P=0.01). We found a significant correlation between late epilepsy onset and the presence of bitemporal IEDs. The mean age at epilepsy onset in UG was 10.1+/-7.9 years, while in BG it was 13+/-9.2 years (P=0.02). CONCLUSIONS: The traditional concept of the evolution of mirror focus cannot apply for humans because the duration of epilepsy does not influence the evolution of bitemporal IEDs. Other factors, i.e. age at onset and seizure frequency may play a role in this process. The association between the higher seizure frequency and mirror foci indicates that the development of mirror focus depends on seizures and not on a progressive 'interictal' epileptogenesis.     

Age at onset in a cohort of schizophrenics in Nigeria.

Over a period of 3 years, 340 patients (199 men and 141 women) who met DSM-III-R criteria for schizophrenia and who knew their exact date of birth were interviewed to determine the age at onset of illness. The immediate family's first awareness of psychotic symptoms was used as the index of onset. Men had a significantly earlier mean age at onset (24 +/- 6) than the women (27 +/- 8). By the time they were 30 years of age, 83% of the men and 66% of the women had become ill. The findings are remarkably similar to those of an earlier report in the same cultural setting, and add to the evidence of sex differences in age at onset of schizophrenia.     

Point prevalence of major depressive disorder in a Swedish urban female population

In a representative sample of 800 women in Gothenburg, aged 38-54 years, the point prevalence of major depressive episode according to DSM-III criteria was 6.9%. Of these, 2.9% had a melancholic episode and 4.0% a non-melancholic. There was no age difference between the two groups. The episode duration was less than a year in 65% of both groups. Mean age at initial episode was significantly lower in the melancholic (33.3 years) than in the non-melancholic group (38.7). The melancholics presented symptoms of mental disorder before age 20 in 39% of cases as against 18% of the non-melancholics. None of the depressives had had a manic episode. The prevalence rate of 6.9% is of the same magnitude as rates recently found in other industrialized countries when standardized diagnostic criteria are used. The earlier onset of melancholic major depression might be indicative of etiological differences between melancholic and non-melancholic major depression.     

The motor phenotype of Parkinson's disease in relation to age at onset

Background: Parkinson's disease (PD) is heterogeneous and age at onset may define variation in clinical phenotype. Most previous studies have used various age cut‐offs and have been based on clinical case series. Methods: We have studied the association between clinical features and age of onset in 358 community‐based and regional patients with PD. Results: Tremor at presentation is twice as common in those with onset over 64 years as compared to those with onset under 45 (early onset PD ‐ EOPD) and becomes more common with increasing age at onset (p values for trend ≤ 0.004). Dystonia affects 60% of those with EOPD, shows a curvilinear relationship with age at onset (cubic versus linear p=0.01) with highest risk in patients whose disease began before 48 years. In this study age at onset was a strong predictor of the development of dyskinesias, with younger age associated with a higher risk of dyskinesias. Following multivariable analysis, allowing for possibly confounding factors (disease duration, L‐DOPA dosage, L‐DOPA treatment duration) younger age at onset, (less than 55 years) predicted the development of L‐DOPA induced dyskinesia (odds ratio <45 years 2.1, 95% CI 1.0, 4.8; odds ratio < 55 years 3.8, 95% CI 1.8, 8.0). Only 2/70 (2.9%) EOPD patients carried pathogenic parkin or PINK1 mutations and the clinical differences between early and late onset disease were not explained by the presence of mutations in these genes. Discussion: This study highlights the clinical differences between early and late onset PD, which have important implications for diagnosis and management. © 2011 Movement Disorder Society     

Multiple sclerosis in the Shetland Islands: an update

Annual incidence rates of multiple sclerosis (MS) in the Shetland Islands have been updated from 1938 to 1986. These reveal a significant decline in MS incidence beginning between 1951 and 1968. No significant change in prevalence, age-specific prevalence, duration of MS, or mean age of the MS population in Shetland has been found since the last survey in 1974, although a trend towards an older MS population was noted.     

Multiple sclerosis in relation to meat preservation in France and Switzerland

In order to test a recent hypothesis on the possible role of defined agents from wood smoke in the etiology of multiple sclerosis (MS), the practices of meat preservation, as reported in ethnographic bibliography, were analyzed in relation to the MS distribution in France and Switzerland. In both countries, but more so in Switzerland, a significant association between both features could be demonstrated.     

High incidence of Creutzfeldt-Jakob disease in North African immigrants to France

During the 15-year period 1968-1982, 328 French residents died of Creutzfeldt-Jakob disease (CJD); 273 had been born in France (annual mortality rate of 0.38 per million inhabitants). Of the 55 foreign-born cases, 12 came from Tunisia and 11 from Algeria (mortality rates of 4.53 and 0.95 per million). Nearly all of the Tunisians were Jews, and six belonged to two families. These findings complement earlier observations on Libyan-born Israelis, but still do not discriminate between genetic or environmental causal factors, which will require epidemiologic investigation of CJD in North Africa.     

Multiple sclerosis in the two northernmost counties of Norway

The prevalence of MS in the two northernmost counties of Norway increased from 20.6 per 100,000 in 1973 to 31.5 per 100,000 in 1983, the increase being most marked in women. The average annual incidence seems to have been stable over the past 20-30 years. None of the patients had a pure Lapp background (having a Lapp mother and father).     

Pupillary function in early multiple sclerosis

Autonomic pupillary function was assessed with pupillometry in 95 mildly or moderately disabled patients with multiple sclerosis (MS) and 81 healthy subjects. The parasympathetic pupillary function was measured as initial diameter (mm), time to minimum diameter (seconds), reflex amplitude (mm), relative reflex amplitude (%), and maximal constriction velocity (mm/seconds). To reflect the sympathetic pupillary function maximal redilatation velocity (mm/seconds), and time of 75% of redilatation (seconds) were measured. Of MS patients 85-99% were within the reference values of healthy subjects. In MS patients the effect of age was observed in the initial diameter, reflex amplitude, and time of 75% redilatation. There were no such age related effects in healthy subjects. In age adjusted analysis the initial diameter and time of 75% redilatation differed significantly from healthy controls. Autonomic pupillary functions were not associated with fatigue, visual defect, or bladder disturbance, as measured by Fatigue Severity Scale, Kurtzke's Functional System Scales, Expanded Disability Status Scale, or the Multiple Sclerosis Functional Composite. Our results suggest that both parasympathetic and sympathetic pupillary functions are disturbed already early in the course of MS. However, the disturbance is not severe at this stage of the disease. The dysfunction is age-dependent and thus possibly related to the dimished remyelination capacity of the central nervous system.     

Multiple sclerosis in Scandinavia and Finland

Review of studies of incidence of MS over several decades in seven geographical areas scattered over Scandinavia and Finland have shown that incidence rates fluctuate significantly with time in most of the areas but in an inconsistent pattern. The incidence appeared to the lowest in the northernmost parts of Norway indicating that the well-known north-south gradient for risk of MS does not hold true for high latitudes.