Summary The uneven distribution of multiple sclerosis (MS) across populations can be attributed to differences in genes and the environment and their interaction. Prevalence and incidence surveys could be affected by inaccuracy of diagnosis and ascertainment, and prevalence also depends on survival. These sources of error might play a part in the geographical and temporal variations. Our literature search and meta-regression analyses indicated an almost universal increase in prevalence and incidence of MS over time; they challenge the well accepted theory of a latitudinal gradient of incidence of MS in Europe and North America, while this gradient is still apparent for Australia and New Zealand; and suggest a general, although not ubiquitous, increase in incidence of MS in females. The latter observation should prompt epidemiological studies to focus on changes in lifestyle in females. New insights into gene–environment and gene–gene interactions complicate interpretations of demographic epidemiology and have made obsolete the idea of simple causative associations between genes or the environment and MS.

The Changing Demographic Pattern of Multiple Sclerosis Epidemiology

Background: Multiple sclerosis (MS) has been traditionally considered to be more frequent in women and in regions more distant from the equator. However, recent reports suggest that the latitude gradient could be disappearing and that the female-to-male ratio among patients with MS has increased in the last decades. We have conducted a systematic review of incidence studies of MS to assess the overall incidence of MS and explore possible changes in the latitude gradient and the female-to-male ratio over time.

Methods: Systematic review of incidence studies of MS published in Medline between 1966 and February 2007. Age- and sex-specific incidence rates were collected from eligible publications. We computed age-adjusted rates using the world population as standard, and assessed differences in rates according to latitude and period of case ascertainment. Additionally, we evaluated the association between period of case ascertainment and the female-to-male ratio.

Results: The overall incidence rate of MS was 3.6 cases per 100,000 person-years (95% CI 3.0, 4.2) in women and 2.0 (95% CI 1.5, 2.4) in men. Higher latitude was associated with higher MS incidence, though this latitude gradient was attenuated after 1980, apparently due to increased incidence of MS in lower latitudes. The female-to-male ratio in MS incidence increased over time, from an estimated 1.4 in 1955 to 2.3 in 2000.

Conclusion: The latitude gradient present in older incidence studies of multiple sclerosis (MS) is decreasing. The female-to-male MS ratio has increased in the last five decades.

/pdf/temporal-trends-in-the-incidence-of-multiple-sclerosis-a-2tgrz5qal1.pdf

Temporal trends in the incidence of multiple sclerosis: A systematic review

Multiple sclerosis (MS) is the most common cause of neurological disability in young adults worldwide and approximately half of those affected are in Europe. The assessment of differential incidence and prevalence across populations can reveal spatial, temporal and demographic patterns which are important for identifying genetic and environmental factors contributing to MS. However, study methodologies vary and the quality of the methods can influence the estimates. This study aimed to systematically review European studies of incidence and prevalence of MS and to provide a quantitative assessment of their methodological quality. A comprehensive literature search was performed to obtain all original population-based studies of MS incidence and prevalence in European populations conducted and published between January 1985 and January 2011. Only peer-reviewed full-text articles published in English or French were included. All abstracts were screened for eligibility and two trained reviewers abstracted the data and graded the quality of each study using a tool specifically designed for this study. There were 123 studies that met the inclusion criteria. The study estimates were highly heterogeneous, even within regions or countries. Quality was generally higher in the more recent studies, which also tended to use current diagnostic criteria. Prevalence and incidence estimates tended to be higher in the more recent studies and were higher in the Nordic countries and in northern regions of the British Isles. With rare exceptions, prevalence and incidence estimates were higher in women with ratios as high as 3:1. Few studies examined ethnicity. Epidemiological data at the national level was uncommon and there were marked geographical disparities in available data, with large areas of Europe unrepresented and other regions well-represented in the literature. Only 37% of the studies provided standardized estimates. Despite the breadth of the literature on the epidemiology of MS in Europe, inter-study comparisons are hampered by the lack of standardization. Further research should focus on regions not yet studied and the evaluation of ethnic differences in MS prevalence and incidence. National-level studies using current diagnostic criteria, validated case definitions and similar age- and sex-standardization would allow better geographical comparisons.

/pdf/incidence-and-prevalence-of-multiple-sclerosis-in-europe-a-37dnb5dcmm.pdf

Incidence and prevalence of multiple sclerosis in Europe: a systematic review.

Background and aim: Epidemiological studies of multiple
sclerosis suggest a trend of increasing disease
prevalence in susceptible populations. The reasons for this
are unclear and may be the results of methodological
differences between studies, incomplete ascertainment or
advances in technologies that allow the increased
identification of early or mild disease. In addition, direct
comparison of cross sectional prevalence estimates
performed in different epochs in ethnically and geographically
distinct populations may be inappropriate.
Methods: Using detailed phenotypic information and
standardised methodology, a geographically defined
Welsh population was resurveyed after a significant
interval, establishing contemporary prevalence rates and
examining demographic and clinical data to determine
causes of changing disease frequency.
Results: Disease prevalence increased 45% from 101 to
146 per 100 000 population over 20 years. The greatest
increase was observed in women between the ages of 45
and 54 years. No significant increase in disease frequency
was observed in the male population overall, or within
specific age groups. There was no demographic evidence
for a pattern of earlier age at onset or diagnosis to explain
increased disease frequency or decrease in mean age of
the prevalent population. In addition, we failed to identify
a pattern of recognition of patients with less severe
disability. Although there was a modest 13% increase of
2.2 years in mean disease duration, and eight new
previously prevalent patients were identified, the main
cause of rising disease frequency was related to a 2.8-
fold increase in disease incidence for women over
23 years from 2.65 to 7.30/100 000/year increasing the
sex ratio of incident patients from 1.8 to 4.3 (women:-
men).
Conclusion: Recent change in disease incidence and
prevalence in this population is likely to be the result of
environmental factors that have been operative in the
past few decades in women alone and infers avoidable
risk factors. Modelling of current overall incidence
suggests a further increase in prevalence to 260 per
100 000 population within the next 20–40 years. Further
studies are needed in order to identify recent changes in
sex specific environment and lifestyle that confer
susceptibility.

https://jnnp.bmj.com/content/jnnp/80/4/386.full.pdf

Increasing prevalence and incidence of multiple sclerosis in South East Wales

Objective:Changing trends in multiple sclerosis (MS) epidemiology may first be apparent in the childhood population affected with first onset acquired demyelinating syndromes (ADSs). We aimed to determine the incidence, clinical, investigative and magnetic resonance imaging (MRI) features of childhood central nervous system ADSs in the British Isles for the first time.Methods:We conducted a population active surveillance study. All paediatricians, and ophthalmologists (n = 4095) were sent monthly reporting cards (September 2009–September 2010). International Paediatric MS Study Group 2007 definitions and McDonald 2010 MS imaging criteria were used for acute disseminated encephalomyelitis (ADEM), clinically isolated syndrome (CIS) and neuromyelitis optica (NMO). Clinicians completed a standard questionnaire and provided an MRI copy for review.Results:Card return rates were 90%, with information available for 200/222 positive notifications (90%). After exclusion of cases, 125 remained (age range 1.3–15.9), ...

/pdf/paediatric-acquired-demyelinating-syndromes-incidence-526fo5kwr5.pdf

Paediatric acquired demyelinating syndromes: incidence, clinical and magnetic resonance imaging features

Study objective: The objectives of the study were to establish the prevalence and incidence of multiple sclerosis in Glasgow and to assess the epidemiological importance of deprivation and...

Epidemiology of multiple sclerosis in Glasgow.

A retrospective cohort study was carried out of new referrals to transient ischaemic attack (TIA) clinics in Glasgow. The aims of the study were to describe the profile of referrals and to assess the odds ratios for TIA, minor stroke or amaurosis fugax of both cardiovascular risk factors and clinical features. In total, data were collected for 813 new referrals in a period of six months. Thirteen point eight percent of referrals were from other Health Boards. The overall referral rate among residents of Greater Glasgow NHS Board was 165.6 per 100,000 per year. About 20% of referrals were made by clinicians in secondary care. The specialties from which referrals were most commonly made were accident and emergency, general medicine, ophthalmology and geriatric assessment. The most common risk factors in patients referred were hypertension (52.9%), smoking (31.7%), ischaemic heart disease (22.7%) and former smokers (22.4%). The most common clinical features were hemiparesis (13.3%), weakness of an upper limb (8.7%), vertigo (7.9%) and dysphasia (7.3%). In 48.7% of cases, a non-cerebrovascular diagnosis was made. Separate multivariate models were established for risk factors and clinical features. In the model for risk factors, five factors were significant for risk of TIA, stroke or amaurosis fugax. These were hyperlipidaemia, age over 64 years, hypertension, smoking and ex-smoking. In the model for clinical features, five factors were also significant. These were visual field defect, speech defact, facial weakness and hemiparesis.

Epidemiological aspects of referral to TIA clinics in Glasgow

Can thyroid surgery be decided based on ultrasonographic findings, irrespective of cytopathological findings? Five-year retrospective study in a district general hospital.

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Epidemiology of multiple sclerosis in Glasgow.

Epidemiological aspects of referral to TIA clinics in Glasgow

Can thyroid surgery be decided based on ultrasonographic findings, irrespective of cytopathological findings? Five-year retrospective study in a district general hospital.