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.
Statistics Canada data were used to calculate multiple sclerosis (MS) mortality rates per 100,000 population in the Canadian provinces from 1965 to 1994. For the period 1965-1994, the highest average annual MS mortality rates were in Quebec (4.4) and Ontario (3.9), while the Western Provinces had an intermediate rate (2.1) and the Atlantic Provinces had the lowest rate (1.2). Female mortality rates exceeded male rates in each of the four regions. Average annual MS mortality rates in Canada overall fluctuated during the past 30 years, with rates of 3.4 in 1965-1969, 4.2 in 1970-1974, 3.2 in 1975-1979, 2.3 in 1980-1984, 2.8 in 1985-1989 and 3.9 in 1990-1994. Female mortality rates exceeded male rates during each 5-year period. The highest mortality rates for both genders were in the 65 years plus age group. Rates in the under 45 years age group have remained stable, while rates in both the 45-64 and 65 years plus age groups have fluctuated. There is no apparent relationship between prevalence and mortality rates among the Canadian provinces.
At the University of Alberta's multiple sclerosis research clinic 100 patients with multiple sclerosis were matched to control patients for age, sex, race and zone of residence before the age of 15 years. Case and control subjects were interviewed and information was collected by questionnaire on factors that might play a role in the development of multiple sclerosis. The only factors found to be significantly associated with the development of this disorder were a history of leisure time spent in physical activities before the onset of symptoms, exposure to animal illness -- specifically canine distemper -- and a history of severe or prolonged emotional stress. The study also confirmed a familial predisposition to multiple sclerosis and suggested a relation between the disorder and a personal or family history of diabetes mellitus.
Research has produced conflicting findings about whether there is an excess of like-sexed pairs among concordant multiple sclerosis (MS) sibships. Although a positive correlation in onset age among sibling pairs overall has been reported, no data have been published describing age at onset correlations for like-sexed versus unlike-sexed pairs. The purpose of this study was to provide additional information on both issues.
Patients with an MS sibling were sought through the files of the University of Alberta MS clinic (Edmonton, Canada). The clinic neurologist either reviewed clinical/autopsy material or assessed relatives of index cases prior to accepting the relative as having MS. Pairs of siblings (excluding twins) were divided into (1) male-male pairs, (2) female-female pairs, and (3) female-male pairs.
A total of 62 concordant sibling pairs were identified. There were 33 like-sexed pairs (6 male-male/27 female-female) and 29 unlike-sexed pairs. The observed number of like-sexed pairs was not significantly different from the expected frequency using 2 x 2 chi2 analysis, where expected values represent the binomial distribution predicted from the frequency of each sex as determined by total number of males and females. The age at onset intraclass correlation coefficient was -0.09 for sibling pairs overall, -0.22 for like-sexed pairs and +0.02 for unlike-sexed pairs.
This study does not provide evidence for an association between disease susceptibility and gender in siblings concordant for MS; nor does it suggest that genetics plays a role in onset age.
Self-reported population ancestry data for the 19 census divisions (CDs) of Alberta, Canada, were correlated with multiple sclerosis (MS) prevalence rates in those divisions, for men and women separately; and parental ancestry was compared between a group of MS patients and controls attending the University of Alberta MS Clinic. At the CD level, there was a positive correlation between single Scandinavian ancestry and MS prevalence in men, but this was not confirmed in the case-control comparison. The case-control comparison indicated an excess risk of MS associated with single non-specific European as opposed to British ancestry in men only. When paternal versus maternal ancestry was considered separately, there was an excess risk of MS associated with non-specific European as opposed to British ancestry for both men and women, but on the father's side only. Aboriginal ancestry was negatively associated with MS prevalence at the CD level in both men and women; and no MS patients with aboriginal origin were among cases assembled through the MS clinic.
We report a prevalence study of multiple sclerosis (MS) in the town of Westlock and surrounding county of Westlock, in Alberta, Canada. The prevalence rate for clinically definite MS on January 1, 1991, was 200/100,000. The average annual incidence rates for patients living in the area at onset were 1.91/100,000 for 1950-1959, 2.85/100,000 for 1960-1969, 3.82/100,000 for 1970-1979, and 7.26/100,000 for 1980-1989. Forty-eight percent of the patients were relapsing-remitting. Sixty percent were still walking without assistance. The female-to-male ratio was 1.4:1. Mean current age was 47, age at onset 30, and duration of illness 18 years. The majority of patients (40%) experienced multiple symptom onset. Forty percent were of single ethnic origin (primarily British); the remainder were predominantly north European combinations. Twenty-four percent of patients reported another MS relative, six first-degree and one second-degree relative.
A prevalence study of multiple sclerosis (MS) was carried out in the town of Barrhead and surrounding county of Barrhead, in Alberta, Canada. The prevalence rate for clinically probable/definite multiple sclerosis on January 1, 1990 was 196/100,000. The average annual incidence rates for patients living in the area at onset were 1.31/100,000 for 1950-59, 4.97/100,000 for 1960-69, 3.77/100,000 for 1970-79, and 4.22/100,000 for 1980-89. Fifty percent of the patients were relapsing-remitting. Sixty percent were still walking without assistance. The female-to-male ratio was 1:1. Mean current age, age at onset and duration of illness were 49, 27 and 22 years respectively. The majority of patients (40%) experienced multiple symptom onset. Fifty percent were of single ethnic origin (either British or German); the rest were predominantly North European combinations. Forty percent of patients reported another MS relative. MS had affected the work status of 60% of the patients, 15% of whom were confined to an extended care centre.
Some investigators have suggested that there are different forms of multiple sclerosis (MS) based on onset age, and that each has a different etiology. 173 Canadian MS patients were matched to controls on age, gender, race and risk zone prior to age 15. Data were collected on: age at onset, gender, initial symptom, disability level, residence history and family background. Three onset age subgroups (early, intermediate and late) were derived. Matched-pair logistic regression analysis indicated that rural residence, use of well water and an MS family history distinguished between patients and controls overall, but showed no significant interaction with onset age. A family history of diabetes distinguished between patients and controls with evidence of age interaction, in that this risk factor decreased in importance as onset age increased.