Regional variation in multiple sclerosis prevalence in Australia and its association with ambient ultraviolet radiation

The aim of this study was to conduct an ecological analysis of the extent to which ultraviolet radiation (UVR) levels might explain the regional variation of multiple sclerosis (MS) in Australia. MS prevalence data for six Australian regions were compared with UVR levels of the largest city in each region, with some other climatic variables and with the melanoma incidence in the same regions. A close association was found between the theoretical MS prevalence predicted from UVR levels and the actual prevalence. Furthermore, the negative correlation between UVR and MS prevalence (r = -0.91, p = 0.01) was higher than the positive correlation observed for UVR and malignant melanoma incidence (r = 0.75, p = 0.15 for males and r = 0.80, p = 0.10 for females). This study demonstrated that the regional variation in MS prevalence in the continent of Australia could be closely predicted by regional UVR levels. It is consistent with the hypothesis that UVR exposure may reduce the risk of MS possibly via T-lymphocyte-mediated immunosuppression. Analytical epidemiology studies are required to investigate this specific hypothesis.     

Regional variations in the prevalence of multiple sclerosis in French farmers

Background

Studies on the prevalence of multiple sclerosis have been carried out worldwide, showing a heterogeneous distribution between countries and even between the different regions of the same country.

Methods

We estimated the regional and national prevalence of multiple sclerosis in France on 1 January 2003, based on the computerised database of the national farmer health insurance system (“Mutualité Sociale Agricole”).

Results

There were 2667 cases of multiple sclerosis registered on the prevalence date, out of 4 098 477 affiliates. After standardisation on age, estimates for the national prevalence of multiple sclerosis in French farmers were 65.0 per 100 000 inhabitants (95% confidence interval 62.5 to 67.5), 41.9 per 100 000 in men (39.1 to 44.7) and 96.3 per 100 000 in women (92.0 to 100.6). The prevalence of multiple sclerosis was significantly higher in the north eastern regions (approximately 100 per 100 000 inhabitants) compared with the south western regions (around 50 per 100 000 inhabitants).

Conclusion

Our study is the first to evaluate the overall prevalence of multiple sclerosis in France and its 22 regions using the same methodology. Our results may be generalised to the whole French population as there is no convincing evidence of an increased or decreased susceptibility to multiple sclerosis among farmers or persons living in the countryside. This places France among the countries of medium to high prevalence. Confirming the uneven distribution of multiple sclerosis that correlates with latitude, raises once more the question of the role of genetic and environmental factors in the susceptibility to multiple sclerosis.Studies on the prevalence of multiple sclerosis (MS) have been carried out worldwide, showing a heterogeneous distribution of cases between countries. This heterogeneity seems to correlate with latitude, with an increasing south to north gradient in the Northern hemisphere. Whether this gradient is caused by genetic or environmental factors remains a matter of debate.^1,2,3 France is considered a country of medium to high prevalence for MS.^4,5,6,7,8 To date, there has been no overall estimate of the prevalence of MS in France using the same methodology for all regions. The Mutualité Sociale Agricole is the second health insurance system in France. It has exclusive coverage of farmers and farm workers, as well as their spouses and children, provided they do not work outside the farm. Our objective was to estimate the overall prevalence of MS in France and in each of its 22 administrative regions.     

Contribution of incidence to increasing prevalence of multiple sclerosis in Alberta, Canada

Alberta Health Care Insurance Plan (AHCIP) data were used to calculate prevalence and incidence rates for multiple sclerosis (MS) in the general population of Alberta from 1990 to 2004. Multiple sclerosis prevalence rose steadily each year over this time period, from 217.6/100,000 individuals in 1990 to 357.6/100,000 in 2004. Multiple sclerosis incidence fluctuated with a slight increase from 1990 to 2004, at 20.9/100,000 and 23.9/100,000, respectively. Age-specific prevalence rates were higher between ages 30 and 60 in 2004 than in 1990. The pattern of age-specific incidence rates was similar in 1990 and 2004, with a slight shift toward diagnosis in younger years. Gender-specific prevalence rates were higher for females in both 1990 and 2004, with a greater increase in females (43%) than males (29%). Gender-specific incidence rates were higher for females than males in both years, but there was no differential increase in incidence by gender from 1990 to 2004. The 2004 Alberta MS prevalence rate remains among the highest reported worldwide. Both increasing incidence and longer duration have likely contributed to increasing MS prevalence in the province.     

Increasing prevalence of multiple sclerosis in Finland

Objectives – To follow‐up the prevalence trends of MS from 1983 to 1993 in western and southern Finland. MS epidemiology has been previously followed from 1964 to 1978 in these regions. The updated prevalences were correlated with incidence trends in the same period. Methods– Age‐adjusted and age‐specific MS prevalence rates were calculated for cases classified by Poser's criteria. Results– In the western health‐care districts, Seinäjoki and Vaasa, prevalences in 1993 were 202/10⁵ and 111/10⁵. In the southern district Uusimaa the respective figure was 108/10⁵. In Seinäjoki a significant 1.7‐fold increase was found in 1993 as compared to 1983, mainly due to increased incidence. In Uusimaa a significant 1.2‐fold increase in prevalence was found in the presence of stable incidence. In Vaasa prevalence was stable, although incidence was declining. Conclusion– The prevalence of MS is increasing in Seinäjoki and Uusimaa but not in Vaasa. Both the prevalence and incidence in Seinäjoki are now among the highest reported.     

Seasonal variation in multiple sclerosis relapse

Relapses are a characteristic clinical feature of multiple sclerosis (MS), but an appreciation of factors that cause them remains elusive. In this study, we have examined seasonal variation of relapse in a large population-based MS cohort and correlated observed patterns with age, sex, disease course, and climatic factors. Relapse data were recorded prospectively in 2076 patients between 2005 and 2014. 3902 events were recorded in 1158 patients (range 0–24). There was significant seasonal variation in relapse rates (p < 0.0001) and this was associated with monthly hours of sunshine (odds ratio OR 1.08, p = 0.02). Relapse rates were highest in patients under the age of 30 (OR 1.42, p = 0.0005) and decreased with age. There was no evidence of different relapse rates for males compared to females (OR 0.90, p = 0.19). Identification of potentially modifiable environmental factors associated with temporal variation in relapse rates may allow alteration of risk on a population basis and alteration of outcome of established disease once established. Future epidemiological studies should examine dynamic environmental factors with serial prospective measurements and biological sampling. Significant seasonal differences in relapse rates highlight the importance of environmental factors in disease expression and should be taken into account when planning clinical trials in which relapse frequency is an outcome. In addition, identification of potentially modifiable factors associated with this variation may offer unique opportunities for alteration of risk of relapse and long-term outcome on a population level, and suggest putative biological mechanisms for relapse initiation.     

Regional and temporal variation in the incidence of multiple sclerosis in Finland 1979-1993

Previous surveys in Finland from the 1960s have documented an uneven geographic distribution of multiple sclerosis (MS). In the present study, the incidence of MS was studied during 1979-1993 in the western Vaasa and Sein?joki regions and in southern Uusimaa. The overall difference between the western and southern regions persisted; 8.7 per 100,000 in the western, and 5.1 per 100,000 in the southern region. The incidence of 11.6 per 100,000 in Sein?joki was more than twofold greater than the 5.2 per 100,000 incidence found in neighboring Vaasa. An increasing incidence trend was observed for men in Sein?joki, and a decrease for both sexes in Vaasa, while in Uusimaa the incidence remained stable for both sexes. The different incidence trends could not be readily explained by differences in case ascertainment but suggest the effect of environmental factors that have modulated the incidence of MS during the 15-year study period.     

Latitudinal variation in the prevalence of multiple sclerosis in Ireland, an effect of genetic diversity

BACKGROUND: Northern Ireland has a high and rising prevalence rate of multiple sclerosis (MS). The most recent survey in 1996 found a rate of 168.7/100 000. Recorded prevalence rates for the south of Ireland, including County Wexford, have been markedly lower and seemed to suggest the existence of a prevalence gradient within the island. OBJECTIVES: To compare the prevalence of multiple sclerosis in Co. Wexford in the south east of Ireland and Co. Donegal in the north west, and to establish whether a variation in prevalence of MS exists within Ireland. METHODS: Patients were referred from multiple sources. Review of clinical case records and/or patient examination confirmed the diagnosis. RESULTS: In Co. Wexford, 126 patients were found to have clinically definite or probable multiple sclerosis with a prevalence rate of 120.7/100 000 (95% confidence intervals (CI) 100.6 to 143.8), which is similar to other areas of similar latitude within the British Isles. In Co. Donegal, 240 people had clinically definite or probable MS with a prevalence rate of 184.6/100 000 (95% CI 162.0 to 209.5). The difference in prevalence rates is statistically significant (Z = 3.94, p = <0.001). CONCLUSION: There is a latitudinal variation in the prevalence rate of MS between the north and the south of Ireland. The increased prevalence of MS seen in Co. Wexford is likely to represent better case ascertainment and improved diagnostic accuracy rather than an actual increase in prevalence. The north/south variation in prevalence may represent a variation in the genetic predisposition to MS between the background populations of the two counties.     

Estimated prevalence of multiple sclerosis in Italy in 2015

Italy is a high risk area for multiple sclerosis (MS) as confirmed by the numerous prevalence and incidence studies conducted in several regions/districts of the country. Nevertheless, there are no recent published epidemiological data, nor studies about the total prevalence of MS in Italy. Our aim was to update as of 2015 the prevalence rates of MS in different geographical areas using already published epidemiological studies, and to estimate the overall prevalence of the disease in Italy. We made a search in MEDLINE database of all published studies on epidemiology of MS in Italy. Then, we applied, to the already published prevalence data, the last published incidence and mortality rates to recalculate, as of 2015, the prevalence of MS. So, we calculated the mean prevalence rate from our extrapolations, and we applied it to the population in 2015 to estimate the number of MS patients in Italy. Our prevalence extrapolations ranged from 122 to 232 cases/100,000 in the mainland and Sicily, with an average of 176/100,000, and from 280 to 317 cases/100,000 in Sardinia with an average of 299/100,000. Applying these media to the Italian population in 2015, we obtained an estimate of more than 109,000 MS patients in Italy. Our estimates were higher than the latest published rates but consistent with the annual increase of prevalence due to incidence that exceeds mortality, with the increase of survival and, maybe, with the probable increase of incidence.     

Seasonal variation of multiple sclerosis exacerbations in Japan

Abstract. Several reports have described the seasonal variation of multiple sclerosis (MS) attacks in the European countries and in the US. Some have insisted that attacks occurred more frequently in winter or spring. We investigated the possibility of a seasonal variation in the frequency of MS attacks among patients in Japan. A total of 172 MS exacerbations in 34 MS patients were analyzed retrospectively. Attacks were divided into two groups: opticospinal type and brain type. The 12 months of the year were assigned to 6 groups based on average monthly temperature. Of the 172 MS exacerbations, 123 were opticospinal type and 49 were brain type of attacks. The total number of attacks was significantly more frequent in the warmest (July and August) and coldest (January and February) months. The heat of summer in warmer, low latitude areas may be a risk factor for MS attacks.     

Seasonal variation of multiple sclerosis exacerbations in Arizona

We studied 178 MS patients and 82 controls for 5 years. A monthly pattern in in the frequency of exacerbations in Arizona differed from the patterns seen in other regions of the world. Exacerbations were most common in warmer months. No explanation for this was found. In this prospective study, the frequency of viral infections in the MS patients was lower than in the controls.     

A prevalence survey of multiple sclerosis in Sussex.

A first survey of the Brighton and Mid-Downs health districts in Sussex showed a prevalence of multiple sclerosis of 111 per 100,000 (95% confidence interval (95% CI) 103-120) in a population of 596,594 on prevalence day, 1 July 1991. Cases were notified by multiple sources and to maximise case notification patients were not contacted. Cases were classified by hospital and family practitioner notes. The Poser criteria were used for classification. These criteria are precise and exclude cases of isolated spinal cord syndrome. The Allison and Millar criteria used in the surveys in Scotland may lack specificity and it is concluded that the high prevalence of multiple sclerosis in Scotland needs to be reassessed with the more precise criteria. Until this is done, the latitude effect within the United Kingdom remains not proved.     

High prevalence of restless legs syndrome in multiple sclerosis

Prevalence of restless legs syndrome (RLS), a clinically defined disorder, varies from 2.5 to 15% among populations. In the French adult population, prevalence is estimated to be 8.5%. RLS is often secondary to a variety of disorders. Neurological conditions usually associated with RLS are neuropathies and Parkinson's disease. There are few studies of its association with multiple sclerosis (MS). The aim of this study was to estimate RLS prevalence in a population of French MS patients. During one month, 17 neurologists from the G-SEP group prospectively recruited 242 patients who fulfilled the Mc Donald criteria for MS. Each patient underwent a standardised questionnaire to verify the international criteria of RLS. We collected date of birth, gender, MS course (relapsing remitting, primary progressive and secondary progressive) and MS duration. Forty-one subjects (18%) met the criteria for RLS. Comparing the RLS group with the group without RLS, no significant differences were found in age, gender and MS duration. RLS was more prevalent in the relapsing remitting MS group. Prevalence of RLS seems to be doubled in MS patients compared to the general population. This finding warrants further study. Identification of this syndrome in MS patients might lead to specific treatments.     

Incidence and prevalence of multiple sclerosis in southeastern Iran

Background

Based on data available, Iran is located in a low risk area for multiple sclerosis (MS). The objective of the current study is to determine the age and sex adjusted prevalence and incidence of MS in southeastern Iran.

Methods

This cross-sectional case register study was conducted from January to August 2010. Considering that MS affects people aged between 16 and 50 years, we intended to find the incidence and prevalence of MS during this age range. Since all cases in this area are referred to our university hospital for confirmation of diagnosis, misdiagnosis is rare. Population data, based on the censuses carried out in 1996 and 2006, were obtained from the Iranian Bureau of Statistics to determine the number of people at risk.

Results

Totally 206 patients were identified according to the McDonald criteria. In 2009 the age-adjusted prevalence and incidence rates of MS for 16–50 year-old adults were 13.96 and 2.67 per 100,000 persons, respectively. Based on those values; the female to male ratio was 2.18. Between 2006 and 2009, the incidence rates increased 2.4 and 2.7 times in women and men, respectively. In 2009, the prevalence rates among the age ranges of <15, 16–35, 36–50 and ≥51 years were 1.44, 14.34, 12.24 and 1.45 per 100,000 persons, respectively, and the relapsing-remitting type of MS was the most prevalent form (65.8%).

Conclusion

According to the Kurtzke geographical distribution, the authors conclude that the prevalence of MS in southeastern Iran is in the intermediate range, and the incidence rate is showing a faster growth rate, compared to previous years.     

High prevalence of restless legs syndrome in multiple sclerosis

Despite the fact that multiple sclerosis (MS) patients often include leg restlessness as a sensory symptom, MS is not mentioned amongst symptomatic restless legs syndrome (RLS) forms. The aim of this study was to estimate RLS prevalence in a large population of MS patients, comparing clinical and MRI findings between patients with and without RLS. Each of the 156 MS patients (100 females, 56 males, mean age 40.7 ± 10.4) enrolled in a prospective study underwent a medical history interview, a neurological examination with the assessment of the Expanded Disability Status Scale (EDSS), and a structured questionnaire to verify the presence and features of RLS. Conventional brain–spinal MRIs of 99 subjects were also evaluated and compared between patients with and without RLS. Fifty-one subjects (32.7%) (mean age 43.8 ± 12.8) met the criteria for RLS. In a few patients (8.5%), the RLS preceded clinical MS onset, whilst in the remaining cases the RLS was followed by or was simultaneous with clinical MS onset. Comparing the RLS group with the group without RLS, no significant differences were found in MS duration, gender, and referred sleep habits. The primary progressive MS course was more represented in the RLS group, which also showed a higher EDSS score. RLS is a very common finding in MS patients and should be considered amongst the symptomatic RLS forms. RLS is also associated with higher disability.     

The incidence and prevalence of reported multiple sclerosis

A national survey, sponsored by the National Institute of Neurological and Communicative Disorders and Stroke, to determine the incidence, prevalence, and economic impact of multiple sclerosis has just been completed. These data are the first report of the results. Based on the data gathered, it is estimated that on Januaryuary 1, 1976, there were a reported 123,000 multiple sclerosis patients in the conterminous United States (a rate of 58 per 100,000). The annual incidence for the period 1970–1975 was estimated to be 8,800 (a rate of 4.2 per 100,000). The pattern of the disease being more common among females, whites, persons aged 30 to 50 years, and individuals living above the 37th parallel was also demonstrated. In addition to demographic characteristics, selected disease characteristics of the incidence and prevalence populations were also examined.