Highlights
- •The distribution of the educational level was the same in cases and controls before clinical onset for both sexes.
- •The “hygiene hypothesis” could not be confirmed by our study.
- •Working in agriculture may show association with a higher MS risk in women.
- •MS was not associated with a greater exposure to infective agents due to cohabitation with children.
Abstract
Background
The incidence of multiple sclerosis (MS) in Denmark has doubled in women since 1970,
whereas it has been almost unchanged in men. The rapid epidemiological changes suggest
that environmental factors may modify the risk of MS.
Objectives
To investigate whether occupational, physical, or social environmental influence the
risk of MS differently in women than in men.
Methods
The cohort consists of all 1403 patients (939 women, 464 men) identified through Danish
Multiple Sclerosis Registry aged 1–55 of years at clinical onset between 2000 and
2004, and up to 25 control persons for each case, matched by sex, year of birth and
residential municipality. The same cohort was previously used to investigate the influence
of the reproductive factors on the risk of MS.
Results
By linkage to Danish population registers we found a slight albeit statistically significant
excess for 6 female MS patients who had been employed in agriculture: OR 3.52; 95%
CI 1.38–9.00, p=0.008 (0.046 when corrected for multiple significance) and a trend for exposure to
outdoor work in 12 : OR 1.94, 95% CI 1.06–3.55, p=0.03 (0.09 when corrected for multiple significance), but the numbers of cases were
small, and the effects were not found in men. Educational level, housing conditions
in youth, or the presence of children unrelated by blood in the household did not
influence the risk of MS.
Conclusions
Our study did not reveal any additional factors beyond the previously published childbirths
which could explain the extent of the MS incidence increase in women.
Keywords
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Article info
Publication history
Published online: July 21, 2014
Accepted:
July 15,
2014
Received in revised form:
July 14,
2014
Received:
January 15,
2014
Identification
Copyright
© 2014 Elsevier B.V. Published by Elsevier Inc. All rights reserved.
