Ischemic stroke subtypes: a population-based study of incidence and risk factors

BACKGROUND AND PURPOSE: There is scant population-based information on incidence and risk factors for ischemic stroke subtypes. METHODS: We identified all 454 residents of Rochester, Minn, with a first ischemic stroke between 1985 and 1989 from the Rochester Epidemiology Project medical records linkage system. We used Stroke Data Bank criteria to assign infarct subtypes after reviewing medical records and brain imaging. We adjusted average annual incidence rates by age and sex to the US 1990 population and compared the age-adjusted frequency of stroke risk factors across ischemic stroke subtypes. RESULTS: Age- and sex-adjusted incidence rates (per 100 000 population) were as follows: large-vessel cervical or intracranial atherosclerosis with >50% stenosis, 27; cardioembolic, 40; lacuna, 25; uncertain cause, 52; other or uncommon cause, 4. Sex differences in incidence rates were detected only for atherosclerosis with stenosis (47 [95% CI, 34 to 61] for men; 12 [95% CI, 7 to 17] for women). There was no difference in prior transient ischemic attack and hypertension among subtypes, and diabetes was not more common among patients with lacunar infarction than other common subtypes. CONCLUSIONS: The age-adjusted incidence rate of stroke due to stenosis of the large cervicocephalic vessels is nearly 4 times higher for men than for women. There is no association between preceding transient ischemic attack and stroke mechanism. Diabetes and hypertension are not more common among patients with lacunae. Age- and sex-adjusted incidence rates for ischemic stroke subtypes in this population can be compared with similarly determined rates from other populations.     

Parkinson''s disease and essential tremor in families of patients with early-onset Parkinson''s disease.

The occurrence of Parkinson's disease and of essential tremor was examined in the parents and siblings of 52 Parkinson's disease patients with onset before the age of 45 years. The expected numbers of cases with Parkinson's disease or essential tremor were calculated according to the age and sex specific incidence rates of Parkinson's disease and essential tremor in the general population. Among the parents, there was one case of Parkinson's disease (expected 1.2), and 10 cases of essential tremor (expected 5.4); among the siblings there were two cases of Parkinson's disease (expected 0.7), and three cases of essential tremor (expected 5.3). The observed and expected incidence of Parkinson's disease or essential tremor were not significantly different. This does not support the inheritance of early-onset Parkinson's disease, or the association of Parkinson's disease with essential tremor.     

The incidence of major stroke subtypes in Southern Italy: a population‐based study

Background and purpose: Stroke is characterized by well‐defined clinical major subtypes, but there are few studies on incidence rates, aetiologies and outcomes in population‐based setting. We assessed the age/sex incidence of the major stroke subtypes in a region of Southern Italy. Methods: We established a multisource, prospective population‐based register in Puglia, Southern Italy to identify all residents with a first‐ever stroke between 1 January 2001 and 31 December 2002. Results: One hundred and twenty‐seven first‐ever strokes were diagnosed, and stroke subtype was defined in 119 cases. The incidence rates per 100 000 adjusted to the European population (AEP) were 112 for cerebral infarction (CI), 30 for intracerebral haemorrhage (IH), four for subarachnoid haemorrhage (SH) and nine for undetermined stroke (US). The incidence rates for CI, IH and US approximately doubled with each decade of life and were higher in men. AEP incidence rates for CI in the age groups 45–84 were lower compared to other studies, whilst the corresponding rates for IH were higher. Conclusions: This population had a lower incidence of CI compared to other population‐based studies from Northern Europe and the United States. Furthermore, with the projected increase in the segment of the very old in the general population, our data indicate that both CI and IH will dramatically increase in the near future.     

Study of possible factors associated with age of onset in essential tremor.

Factors associated with the age of onset of essential tremor (ET) have not been studied in detail. Identification of modifiable factors could lead to strategies to delay disease onset and identification of nonmodifiable factors would be useful while counseling at risk individuals. The objective of this study was to identify factors associated with age of onset of tremor in ET. One hundred ninety-five ET cases were enrolled in an environmental epidemiological study. Clinical questionnaires included questions on age of onset, demographics (age, sex, race, education), early-life exposures (birth order, childhood household size), exposures prior to tremor onset (head trauma, well water, rural living, estrogen replacement therapy), and family history. In unadjusted analyses, age of onset was associated with family history of tremor (40.9 +/- 22.0 years for cases with a family history of tremor vs. 57.3 +/- 18.4 years for cases without a history; P < 0.001), history of head trauma, younger current age, greater tremor severity, and white race. Ninety-one percent of cases with onset before age 20 years had a family history of tremor. Age ofonset was not associated with other variables of interest (e.g., sex, well water, rural living). In an adjusted linear regression model, age of tremor onset was strongly associated with family history of tremor (P < 0.001). The familial form of ET is characterized by an earlier age of onset than the sporadic form. This study did not detect any other exposures that modified the age of onset of ET. Follow-up studies are needed to examine additional factors of potential interest.     

Achalasia: incidence,prevalence and survival. A population‐based study

Background Studies of achalasia epidemiology are important as they often yield new insights into disease etiology. In this study, our objective was to carry out the first North American population‐based study of achalasia epidemiology using a governmental administrative database. Methods All residents in the province of Alberta, Canada receive universal healthcare coverage as a benefit. The provincial health ministry, Alberta Health and Wellness, maintains a central stakeholder database of patient demographic information and physician billing claims. We defined an achalasia case as a billing claim submitted for the years 1996–2007 with an ICD‐9‐CM code of 530.0 or 530 and a Canadian Classification of Procedure treatment code of 54.92A (endoscopic balloon dilation) or 54.6 (esophagomyotomy). A preliminary validation study of the case definition demonstrated a sensitivity of 85% and specificity of 99% for known cases and controls. Key Results A total of 463 achalasia cases were identified from 1995 to 2008 (59.6% males). Mean age at diagnosis was 53.1 years. In 2007, the achalasia incidence was 1.63/100 000 (95% CI 1.20, 2.06) and the prevalence was 10.82/100 000 (95% CI 9.70, 11.93). We observed a steady increase in the overall prevalence rate from 2.51/100 000 in 1996 to 10.82/100 000 in 2007. Survival of achalasia cases was significantly less than age–sex matched population controls (P < 0.0001). Conclusions & Inferences Using a population‐based approach, the incidence and prevalence of treated achalasia is 1.63/100 000 and 10.82/100 000, respectively. The disease appears to have a stable incidence but a rising prevalence. Survival of achalasia cases is significantly less than age‐matched healthy controls.     

Incidence of intracerebral and subarachnoid haemorrhage in southern Sweden

OBJECTIVES: Spontaneous intracranial haemorrhage-that is, mainly subarachnoid haemorrhage (SAH) and primary intracerebral haemorrhage (PICH)-constitutes an important part of all strokes. As previous epidemiological studies have demonstrated highly variable incidence rates, we conducted a large prospective investigation of all haemorrhagic strokes during a 1 year period. METHODS: Twelve hospitals serving a defined population of 1.14 million in southern Sweden registered all cases with spontaneous intracranial haemorrhage, including those found dead outside hospitals, during 1996. All patients were examined with CT of the brain or underwent necropsy. Incidence rates adjusted to the Swedish population for age and sex, as well as location of haematoma and prevalence of risk factors were calculated. RESULTS: A total of 106 patients with SAH and 341 patients with PICH were identified. The annual incidence/100 000 was 10.0 (6.4 for men and 13.5 for women) for SAH and 28.4 (32.2 for men and 24.7 for women) for PICH when adjusted to the Swedish population. Subarachnoid haemorrhage affected twice as many women as men. The incidence of both types of haemorrhage increased with advancing age, but in particular, this was the case for supratentorial PICH. Lobar haematomas were the most common (51.6%) type of PICH. Among patients with PICH, 37% had hypertension, 41% other vascular disease, and 12% were on oral anticoagulation. Among patients with SAH, 28% had hypertension and 18% vascular disease before the haemorrhage but no one was on treatment with oral anticoagulation. CONCLUSIONS: The incidence of PICH was high, especially for the older age groups. PICH was, on average, three times as common as SAH. The study underscores the importance of PICH and SAH as significant stroke subgroups.     

Subarachnoid hemorrhage incidence among Whites, Blacks and Caribbean Hispanics: the Northern Manhattan Study

American blacks and Hispanics may have a greater incidence of subarachnoid hemorrhage (SAH) than whites, but incidence data are scant. We used an active hospital and community surveillance program and autopsy reports to identify incident SAH cases among white, black and Hispanic adults living in Northern Manhattan between July 1993 and June 1997. The annual incidence adjusted for age and sex to the 1990 US Census was 9.7 per 100,000 (95% CI 7.5-12.0). Compared with whites (9 cases, age- and sex-adjusted annual incidence 8.2 per 100,000), the rate ratio of SAH was 1.3 (95% CI 0.7-2.4) for Hispanics (34 cases, incidence 10.9), and 1.6 (95% CI 0.8-2.8) for blacks (9 cases, incidence 12.8). The 30-day case fatality rate was 26%. Risk of death increased significantly with age and severity at onset but was not influenced by gender or race-ethnicity.     

Incidence and case fatality rates of stroke subtypes in a multiethnic population: the South London Stroke Register.

OBJECTIVE: To identify sociodemographic differences in the incidence of the subtypes of first ever stroke in a multiethnic population. METHODS: A prospective community stroke register (1995-8) was developed using multiple notification sources and pathological and clinical classifications of stroke. Standardisation of rates was to European and World populations and adjusted for age, sex and socioeconomic status in multivariate analyses. A multiethnic population of 234 533 in south London, of whom 21% are black was studied. RESULTS: A total of 1254 cases were registered. The average age of stroke was 71.7 years with black patients being 11.3 years younger than white patients (p<0.0001). The incidence rate/1000 population was 1.33 (crude) (95% CI 1.26 to 1.41), 1.28 (European adjusted) (95% CI 1.2 to 1.35) with a 2.18 (95% CI 1.86 to 2.56) (p<0.0001) age and sex adjusted incidence rate ratio in the black population. Radiological diagnosis was confirmatory in 1107 (88.3%) with 862 (68.7%) infarction, 168 (13.4%) primary intracerebral haemorrhage, and 77 (6.2%) subarachnoid haemorrhage. Of the cerebral infarction cases 189 (21.9%) were total anterior circulatory, 250 (29%) partial anterior, 141 (16.4%) posterior (POCI) and 282 (32.7%) lacunar infarcts. The black group had a significantly higher incidence of all subtypes of stroke except for POCI and unclassified strokes. The incidence rate ratio (IRR) for men compared with women was 1.34 (95% confidence interval (95% CI) 1.19 to 1.50; p<0.001). The IRR for manual versus non-manual occupations in those aged 35-64 years was 1.64 (95%CI 1.22 to 2.23; p<0.0001). There was a borderline significant increase in adjusted survival at 6 months in the black group 95% (CI 0.61 to 1.03, p=0.078) with a hazard ratio of 0.79 after adjustment and stratification. CONCLUSIONS: Although the black population is at increased risk of stroke and most subtypes of stroke, this is not translated into significant differences in survival. Hence black/white differences in mortality are mainly driven by incidence of stroke. There are striking demographic inequalities in the risk of stroke in this multiethnic inner city population that need to be tackled through interagency working. Although the reasons for the increased risk in the black population are unclear, demographic factors such as socioeconomic status do seem to play a significant independent part.     

Epidemiological study of primary intracranial tumours in elderly people

The incidence of primary intracranial tumours in a well definedpopulation of persons older than 70 years (elderly) who resided inKumamoto prefecture was examined. During the period from 1989to 1995, primary intracranial tumours were diagnosed in 271 elderly people; ofthese, 155 (57.2%) tumours were confirmed microscopically. In a meanpopulation of 216 000 people over the age of 70 years, this yields anaverage annual incidence rate of 18.1 cases/100 000 population/year.The incidence was lower in men (15.2/100 000 population) than women(20.3/100 000 population). The age specific incidence/100 000/yearwas 23.2 for the 70-74 year age group, 18.1 for the 75-79 year agegroup, 15.1 for the 80-84 year age group, and 7.6 for persons olderthan 85 years. The most common tumours were meningiomas (50.6%),followed by malignant gliomas (13.3%), pituitary adenomas (12.9%),schwannomas (6.6%), malignant lymphomas (3.7%), and benignastrocytomas (3.7%).

     

Increased risk of hypertension in patients with anxiety disorders: A population-based study

ObjectiveWe designed this study to examine the prevalence and incidence of hypertension and risk factors in patients with anxiety disorders.MethodsThe National Health Research Institute provided a database of 1,000,000 random subjects for study. We obtained a random sample of 766,427 subjects aged ≥ 18 years in 2005. The differences in the prevalence of hypertension between patients with anxiety disorders and the general population in 2005 were tested by multiple logistic regression adjusted for other covariates, including age, sex, insurance amount, region, urbanicity and depression. The differences in the incidence of hypertension between patients with anxiety disorders and the general population according to age group and sex from 2006 to 2010 were tested by a Cox regression adjusted for the other covariates.ResultsThe prevalence of hypertension in patients with anxiety disorders was higher than that in the general population (37.9% vs. 12.4%, odds ratio, 2.61; 95% confidence interval, 2.52–2.70) in 2005. The average annual incidence of hypertension in patients with anxiety disorders from 2006 to 2010 was also higher than that in the general population (3.63% vs. 1.95%, risk ratio, 1.29; 95% confidence interval, 1.23–1.36). Compared with the general population, patients with anxiety disorders had a higher incidence of hypertension in all age and sex groups.ConclusionsPatients with anxiety disorders had a higher prevalence and a higher incidence of hypertension than that in the general population. Age, male sex, diabetes, and hyperlipidemia were risk factors for hypertension in patients with anxiety disorders.     

Wine drinking and essential tremor: A possible protective role

The purpose of this study was to evaluate the possible association of cigarette smoking, coffee drinking, and wine consumption with essential tremor using a matched case–control design. Cases and controls were enrolled from 6 Movement Disorder centers in central‐southern Italy. Essential tremor was diagnosed according to Bain's criteria. Three unrelated healthy controls (not affected by neurological disorders) per each enrolled case, matched by sex and age (±5 years), were selected. A standardized questionnaire was administered to record demographic, epidemiological, and clinical data. All cases and controls underwent a standard neurological examination. Adjusted odds ratios and 95% confidence intervals were estimated using conditional logistic regression for the matched cases and controls. Eighty‐three patients with essential tremor (38 men and 45 women; mean age, 68.2 ± 8.6 years) and 245 matched control subjects (113 men and 132 women; mean age, 68.4 ± 9.7 years) were enrolled in the study. Multivariate analysis showed a significant negative association between essential tremor and wine consumption preceding the onset of disease (adjusted odds ratio, 0.23; 95% confidence interval, 0.08–0.64; P = .0005) with a significant dose effect (1–2 glass of wine per day: odds ratio, 0.32; 95% confidence interval, 0.10–0.95; P = .04; more than 3 glass of wine per day: odds ratio, 0.14; 95% confidence interval, 0.03–0.62; P = .01). In our sample no association between essential tremor and cigarette smoking or coffee drinking was found. Our data suggest a negative association between wine drinking and essential tremor, which could be explained by the long‐term neuroprotective effect of its antioxidant components. © 2011 Movement Disorder Society     

An epidemiological study of motor neuron disease in Hong Kong.

Worldwide, the incidence of motor neuron disease (MND) has been increasing steadily over recent decades. We reported a follow-up epidemiology study of MND in this locality. We identified the subjects from the computer database of the government hospital system between 1 January 1997 and 31 January 2002 by searching the ICD code starting from 335.xx. Every retrieved case or their records were reviewed and validated by neurologist(s) of the responsible regional hospitals which the patients attended. One hundred and twenty cases from seven regional hospitals (serving 48.05% of the HKSAR population) were identified, validated and confirmed to be MND or related diseases. Ninety-eight new cases were diagnosed during the study period. Average age of onset was 58.76 years; SD 14.12 (28-89) years. Male to female ratio was 1.72:1. Peak age of onset was 60-64 years without sex difference. The adjusted incidence rate was 0.60/100,000/year. The adjusted point prevalence at the prevalence date (31 January 2001) was 3.04/100,000. Despite the incidence and prevalence of MND among Hong Kong Chinese, it remained low compared to worldwide figures, and our data suggested a significant rise of MND or related disease in the last decade. A territory-wide prospective epidemiological study is indicated.     

A reappraisal of the epidemiology of multiple sclerosis in Olmsted County, Minnesota

A review of multiple sclerosis (MS) case reports, using the unified record system at the Mayo Clinic for the Olmsted County population, revealed age- and sex-adjusted prevalence rates per 100,000 persons of 160 for Olmsted County and 173 for Rochester, Minnesota, on January 1, 1985. The annual age- and sex-adjusted incidence rate per 100,000 person-years from 1975 to 1984 for Olmsted County was 6.2 and for Rochester, 6.3. This incidence rate is significantly higher than what had been reported previously in Rochester (3.6/100,000) or in other communities. The estimated 25-year survival of the MS population was 76.2% +/- 4.5% compared with 87.7% for the general US white population of a similar age and sex. Survival for men was less than for women. There was no increase in survival for patients diagnosed with MS in more recent decades. No significant increase was found in cancer or autoimmune disease rates in the MS patients.     

Incidence of epilepsy and predictive factors of epileptic and non-epileptic seizures.

PURPOSE: To estimate the incidence of unprovoked seizures (US) and epilepsy in a general population from the southern part of the Netherlands, in relation to age, sex, etiology and seizure type, and to identify predictive factors of the epileptic and non-epileptic seizures. METHODS: All patients aged > or =14 years with a first seizure or who had undiagnosed seizures before the study period were included. Patients were identified from different sources and were independently evaluated and classified by a team of neurologists. A predictive profile for the occurrence of epileptic and non-epileptic seizures was obtained by stepwise logistic regression analysis. RESULTS: The overall annual incidence was 55/100,000 and 30/100,000 for US and epilepsy, respectively. The age-specific annual incidence of US and epilepsy increased with age and reached 120/100,000 and 62/100,000 for the > or =65 years of age group, respectively. The incidence of epilepsy and US in males was higher than in females and partial seizures prevailed over generalized seizures (40 versus 9/100,000). In up to 35% of the cases with US or epilepsy, the etiology was mainly cerebrovascular disease and brain tumors. Predictors for epileptic versus non-epileptic seizures of organic origin were an epileptiform EEG pattern (OR=0.06) versus a history of hypertension (OR=2.8) or cardiovascular disease (OR=5.4). Strong predictors for seizures of non-organic origin were female sex (OR=2.2) and head injury (OR=2.4). CONCLUSIONS: The incidence of US and epilepsy (overall, and age-, sex-, seizure-specific) was similar to those reported by other developed countries. The predictive factors found in this study may assist in the early diagnosis of seizures.     

Cinnarizine-induced parkinsonism. Susceptibility related to aging and essential tremor

Age at onset in 24 consecutive cinnarizine-induced parkinsonism (CIP) patients referred during a 2-year period was compared with 102 newly referred cases of Parkinson's disease (PD) examined during the same period. Not only did CIP onset occur at a greater age than PD (70.6 + 1.4 years versus 60.1 + 1.1 years), but the number of CIP cases increased steadily with age, whereas the incidence of PD patients peaked between the ages of 55 and 60 years, as is usually the case. At the time of referral, 62% of CIP cases and 14% of PD cases were over the age of 70, suggesting that advanced age was not a source of referral bias. A structured questionnaire prospectively given to 24 CIP patients revealed a history of tremor in at least one family member in 56% of the cases, whereas the incidence was much lower in 124 PD cases (17%) and 102 hospitalized nonneurological patients aged over 65 (6%). Moreover, three of the CIP patients themselves had a history of essential tremor previous to the onset of parkinsonism. CIP patients had frequently been exposed to the drug for years before developing any extrapyramidal symptoms (mean exposure, 4.1 +/- 4 years; range 4 months to 15 years). Though controlled epidemiological studies are needed to evaluate the possibility that cinnarizine is increasingly prescribed in the general population with advancing age, our data suggests that aging plus a background of genetically determined essential tremor represented critical risk factors for development of this drug side effect.     

Descriptive analysis of the activity in a movement disorder unit in a tertiary hospital in Catalonia

INTRODUCTION. Movement disorders are an important part of the activity of a Neurology service, but there are few studies examining their health care demand. AIMS. To analyze the first visits of the Movement Disorders Unit of the Hospital de la Santa Creu i Sant Pau in Barcelona and to compare the results with those of previous studies. PATIENTS AND METHODS. Prospective study of the first neurological assessments carried out during 2010. Demographic variables of patients were collected and diagnoses were reviewed 12 months later. RESULTS. 423 first visits were done (application rate of 1.41 per 1000 inhabitants-year): 54% females, median age 68.8 ± 14.2 years-old. 74.3% of referrals came from the family doctor. The most frequent reasons for consultation were tremor (40%) and parkinsonism-motor clumsiness (26%). The most prevalent diagnoses were Parkinson's disease (36%) and essential tremor (19%). After the first assessment, 84% of patients continued controls in the Unit. One year later, in the 8% of cases there was a change in the initial diagnosis. Taking into account the incidence of each disorder, the number of patients seen was fewer compared to the estimated (19,5 times lower), especially marked in cases of restless legs syndrome, essential tremor and Tourette syndrome. CONCLUSIONS. In our Unit the most frequent reason for consultation is tremor and the most prevalent diagnosis is Parkinson's disease. The number of patients treated is clearly lower than the estimated according to the incidence of the diseases in the population.     

Association between restless legs syndrome and essential tremor.

After observing that several families with essential tremor (ET) clinically cosegregated with restless legs syndrome (RLS), we prospectively evaluated for the presence of RLS in 100 patients presenting to the Baylor College of Medicine with ET and prospectively examined all patients presenting with RLS for the presence of tremor during the same time frame. Of 100 consecutive ET patients (60 women and 75 with a family history of ET) seen over 19 weeks (current age, 65.2 +/- 16.3 years; age at tremor onset, 37.8 +/- 19.9 years) 33 met all criteria for RLS, of which 25 had never been diagnosed previously. A family history of RLS was reported in 57.6% of these 33 patients and was the only significant predictor of RLS in the ET population. Their International Restless Legs Syndrome Rating Scale score was 16.6 +/- 8.1. Over 19 weeks, we also examined 68 consecutive RLS patients (63.2% women and 54.4% with a family history of RLS) for the presence of tremor. Their current age was 55.8 +/- 14.4 years, and age at RLS onset was 33.7 +/- 19.5 years. Overtly pathological tremor was rare, but trace tremor was very common. Overall, we found a very high rate of undiagnosed RLS in patients presenting for tremor, but unlike other "secondary" forms of RLS, this finding was also associated with a high familial history of RLS, suggesting that they share some genetic similarities.     

Hypertension and stroke in centenarians, Okinawa, Japan

OBJECTIVE: To investigate the relationship between a history of hypertension, cigarette smoking and alcohol intake and the lifetime prevalence of stroke in the oldest-old population. DESIGN: A cross-sectional study. SUBJECTS: All of the Japanese centenarians in the Okinawa Prefecture (266 men and 1,378 women). METHODS: Okinawa Prefectural Government conducted health surveys among all of the centenarians in Okinawa. The variables used for analysis were sex, history of stroke, age at the first diagnosis of stroke, history of hypertension, cigarette smoking and alcohol intake. We used multiple logistic regression analysis taking the history of stroke as the dependent variable. RESULTS: The lifetime prevalence value for stroke was 11.0% in Japanese centenarians. Hypertension was independently associated with an increased lifetime prevalence of stroke (adjusted odds ratio = 2.97 and 95% confidence interval: 2.16-4.08). There was no material relationship between sex, cigarette smoking, oralcohol intake and the prevalence of stroke. When the lifetime prevalence of stroke was divided according to whether stroke had been diagnosed for the first time at the age of 90 years or less or over the age of 90, a significant positive association between hypertension and stroke was more pronounced in centenarians with a diagnosis of stroke at the age of 90 years or less than in those over the age of 90. CONCLUSIONS: The findings suggest that hypertension may increase the likelihood of stroke in Japanese centenarians in Okinawa although the association between hypertension and stroke was more pronounced in those having stroke at 90 years or younger.     

Guillain–Barré syndrome in Greece: seasonality and other clinico-epidemiological features

The epidemiologic and clinical features of Guillain-Barré syndrome (GBS) during a 13-year period in a region of south-western Greece with an average population of 819 009 inhabitants are described. Clinical records of all patients between 1 January 1989 and 31 December 2001 who were admitted in the two referring hospitals of the above district and fulfilled the criteria for idiopathic GBS were reviewed. Overall 105 patients were identified. The age adjusted to European population incidence rate per 100 000 person-years was 1.02 (95% CI: 0.84-1.24) and a male preponderance was found. The highest number of cases (35; 33.3%) occurred in spring and the lowest (17; 16.2%) in autumn, although this tendency did not reach a significant level. Cases with and without preceding illness were similarly distributed in the seasons. Electrophysiologic abnormalities of axonal type were found in 6.1% of patients. The mortality rate was 2.8% and the long-term outcome 5%. The incidence of GBS was relatively low and the prognosis was close to the best reported. Spring clustering has also been observed in other countries with mild climate.     

Prevalence and incidence of multiple sclerosis in Oppland County: a cross-sectional population-based study in a landlocked county of Eastern Norway

Risberg G, Aarseth JH, Nyland H, Lauer K, Myhr K‐M, MidgardR. Prevalence and incidence of multiple sclerosis in Oppland County – a cross‐sectional population‐based study in a landlocked county of Eastern Norway.
Acta Neurol Scand: 2011: 124: 250–257.
© 2010 John Wiley & Sons A/S. Objectives – We report the prevalence and incidence rates of multiple sclerosis (MS) in Oppland County, Norway. Methods – Records from all patients diagnosed with MS at the two Oppland County hospitals, Gjøvik and Lillehammer during 1989–2001 were evaluated. In addition, all general practitioners in Oppland County reported their patients into the study. Results – The age‐adjusted prevalence rate of definite MS was 174.4/ 100 000 on the prevalence day 1 January 2002. When the probable cases were included, the prevalence rate rose to 185.6/100 000. The highest prevalence rates were detected in the northern mountain areas, thus corroborating the results from previous local surveys 30–50 years ago. The prevalence of MS was statistically significantly associated with climatic, socioeconomic and geographic variables in the county. The age‐adjusted incidence of definite and probable MS in Oppland County was 6.6/100 000 during 1989–1993 increasing to 7.6/100 000 during 1994–1998. Discussion – We found the highest prevalence rates of MS ever reported in Norway. Our findings indicate a possible influence of environmental factors.