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Infectious mononucleosis (IM) is associated with the risk of developing multiple sclerosis (MS). Using databases of hospital admissions for England (1999-2005), we investigated the female-to-male ratios (FMRs) for admission to hospital for IM and MS stratified by age. Males were more frequently admitted for IM for all age groups apart from ages 10-14 (FMR 1.50; 95% confidence interval (CI) 1.36-1.64) and, borderline significantly, at ages 15-19 (FMR 1.03, 95% CI 0.99-1.08). This intriguing aspect of IM epidemiology in adolescence, the atypical female excess, may be linked to the sex ratio of MS, where females predominate from adolescence.

Objective: It is well recognised that variation in the geographical distribution of multiple sclerosis (MS) exists. Early studies in England have shown the disease to have been more common in the North than the South. However, this could be an artefact of inaccurate diagnosis and ascertainment, and recent data on MS prevalence are lacking. In the present study, data were analysed to provide a more contemporary map of the distribution of MS in England and, as infectious mononucleosis (IM) has been shown to be associated with the risk of MS, the geographical distribution of IM with that of MS was compared., Methods: Analysis of linked statistical abstracts of hospital data for England between 1999 and 2005., Results: There were 56,681 MS patients. The admission rate for MS was higher in females (22/10(5); 95% CI 21.8 to 22.3) than males (10.4/10(5); 95% CI 10.2 to 10.5). The highest admission rate for MS was seen for residents of Cumbria and Lancashire (North of England) (20.1/10(5); 95% CI 19.3 to 20.8) and the lowest admission rate was for North West London residents (South of England) (12.4/10(5); 95% CI 11.8 to 13.1). The geographical distributions of IM and MS were significantly correlated (weighted regression coefficient (r (w))=0.70, p<0.0001). Admission rates for MS were lowest in the area quintile with the highest level of deprivation and they were also lowest in the area quintile with the highest percentage of population born outside the UK. A significant association between northernliness and MS remained after adjustment for deprivation and UK birthplace., Conclusions: The results show the continued existence of a latitude gradient for MS in England and show a correlation with the distribution of IM. The data have implications for healthcare provision, because lifetime costs of MS exceed £1 million per case in the UK, as well as for studies of disease causality and prevention.

Background: The possibility that head injury may influence the development of multiple sclerosis (MS) has been studied inconclusively in the past., Objective: To determine whether head injury is associated with an increased risk of MS., Method: Analysis of database of linked hospital and death records, comparing the occurrence of MS in a cohort of people admitted to hospital with head injury and a reference cohort., Results: The rate ratio for MS after head injury, compared with the reference cohort, was 1.1 (95% confidence interval, 0.88 to 1.36). There was no significant increase in the risk of MS at either short or long time periods after head injury. Using length of hospital stay as a proxy for severity of injury, there was no significant increase in the rate ratio for MS after head injuries with hospital stays of less than two days (rate ratio = 1.1 (0.71 to 1.57)), two or more days (rate ratio = 1.0 (0.68 to 1.45)), or seven or more days (rate ratio = 1.3 (0.64 to 2.34))., Conclusions: The method used, record linkage, ensures that patients' recollection of injury, or any tendency to attribute MS to injury, cannot have influenced the results. Injuries to the head were not associated with either the aetiological initiation or the clinical precipitation of onset of multiple sclerosis.

Objective: To ascertain if infectious mononucleosis is a risk factor for the development of multiple sclerosis (MS); and, if it is, whether its effect is close to or remote in time from the onset of MS., Design: Analysis of database of linked abstracts of records of hospital admission and death., Setting: Health region in central southern England., Main Outcome Measure: Ratio of rate of MS in a cohort of people admitted to hospital with infectious mononucleosis to the rate in a comparison cohort., Results: Considering all time intervals from admission with infection to admission with MS, there was a non-significant increase of risk of MS in the infectious mononucleosis cohort (rate ratio 2.17, 95% confidence intervals 0.79 to 4.77). At the interval of 10 years or more, there was a significant increase in risk of MS (rate ratio 4.01, 1.48 to 8.93). The mean time from infectious mononucleosis to first admission with MS was 14 years., Conclusion: This study adds support to the evidence that Epstein-Barr virus, the cause of infectious mononucleosis, is associated with MS. Its role is probably as an initiator of the disease process of MS, or as a contributor to its early development, rather than as an activator of latent, existing disease.

Objective: The prevalence of multiple sclerosis (MS) varies with latitude: it increases with distance from the equator in both hemispheres. To seek evidence on whether solar radiation is a protective factor for MS, this study investigated whether skin cancer, as an indicator of solar radiation, is less common in people with MS than in others., Design: Analysis of a database of linked hospital records and death certificates., Setting: The Oxford Region of the National Health Service, England., Subjects: A cohort comprising all people in the database with MS, and comparison cohorts of people with other diseases., Results: Skin cancer was significantly less common in people with MS than in the main comparison cohort (rate ratio 0.49; 95% confidence interval 0.24 to 0.91). There was no general deficit of cancer in the MS cohort, and no deficit of skin cancer in cohorts of people with other autoimmune or neurological diseases., Conclusion: The findings support the hypothesis that solar radiation may have a protective influence on the development of MS.