Birth cohort effects in multiple sclerosis.
OBJECTIVE
To identify potential birth cohort effects in multiple sclerosis in Sweden and particularly in Stockholm county.


METHODS
Data on multiple causes of death from multiple sclerosis during 1962 to 1995 in Sweden and 1968 to 1995 in Stockholm county were analyzed using age-period-cohort models and curvature.


RESULTS
Mortality from multiple sclerosis was higher in Sweden than in Stockholm county, with stable time trends, slight period effects and marked age effects. Cohorts born before or after a central period, from 1910 through 1930, registered lower mortality. A periodic wave-form mortality pattern was identified, following a 5-to-6-year cycle for cohorts born before 1925 both in and outside Stockholm county, and changing to longer or irregular cycles for cohorts born after 1930.


CONCLUSIONS
Although methodological constraints inducing the saw-tooth pattern cannot be excluded, these results are consistent with etiologic hypotheses claiming a role for environmental factors in multiple sclerosis.
Jin
Ya-Ping
YP
Neuroepidemiology Unit, Division of Neurology, Karolinska Institute, Huddinge University Hospital, S-141 86, Huddinge, Sweden. Ya-Ping.Jin@neurotec.ki.se
De Pedro-Cuesta
Jesús
J
López-Abente
Gonzalo
G
Link
Hans
H
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D006801:Humans; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000453:epidemiology*; D016012:Poisson Distribution; D013548:Sweden / Q000453:epidemiology