Answers are grounded in this paper and cite their sources.
The incidence of multiple sclerosis (MS) was studied in the county of Hordaland, western Norway. A significant increase in incidence in the period 1958-1987, a decline followed by a gradual increase in mean age at onset, geographic differences in time trends and a biphasic pattern revealed by a birth cohort analysis support the theory of real time-space fluctuations in the incidence of MS over time.
No takes yet. Share an insight, caveat, or question.
Grønning et al. (1991) studied this question.
Synapse has enriched 10 related papers. Consider them for comparative context: