R. Midgard et al., INCIDENCE OF MULTIPLE-SCLEROSIS IN MORE AND ROMSDAL, NORWAY FROM 1950TO 1991 - AN AGE-PERIOD-COHORT ANALYSIS, Brain, 119, 1996, pp. 203-211
We have examined the time trends in multiple sclerosis incidence over
the past four decades from 1950 to 1991 in More and Romsdal County, No
rway. Incidence rates by year of birth, year of onset and year of diag
nosis according to sex, age and clinical course were studied. All pati
ents with multiple sclerosis diagnosed by August 1992 were included, g
iving a total of 419 patients (171 men, 248 women) with onset of multi
ple sclerosis in the period 1950-91. Mean age at onset was 33.2 years,
and mean age at diagnosis was 39.2 years. The incidence rate by year
of onset increased from 2.87 per 100 000 in the period 1950-54 (men 3.
06, women 2.67) to 5.57 per 100 000 in 1985-91 (men 3.75, women 7.94)
(P < 0.001). The incidence was particularly high in the period from 19
75 to 1985. Major period- or cohort-effects in incidence, apart from t
he general increasing trend could not be identified by an age-period-c
ohort analysis.