Season of infectious mononucleosis and risk of multiple sclerosis at different latitudes; the EnvIMS Study.
BACKGROUND
Seasonal fluctuations in solar radiation and vitamin D levels could modulate the immune response against Epstein-Barr virus (EBV) infection and influence the subsequent risk of multiple sclerosis (MS).


METHODS
Altogether 1660 MS patients and 3050 controls from Norway and Italy participating in the multinational case-control study of Environmental Factors In Multiple Sclerosis (EnvIMS) reported season of past infectious mononucleosis (IM).


RESULTS
IM was generally reported more frequently in Norway (p=0.002), but was associated with MS to a similar degree in Norway (odds ratio (OR) 2.12, 95% confidence interval (CI) 1.64-2.73) and Italy (OR 1.72, 95% CI 1.17-2.52). For all participants, there was a higher reported frequency of IM during spring compared to fall (p<0.0005). Stratified by season of IM, the ORs for MS were 1.58 in spring (95% CI 1.08-2.31), 2.26 in summer (95% CI 1.46-3.51), 2.86 in fall (95% CI 1.69-4.85) and 2.30 in winter (95% CI 1.45-3.66).


CONCLUSIONS
IM is associated with MS independently of season, and the association is not stronger for IM during spring, when vitamin D levels reach nadir. The distribution of IM may point towards a correlation with solar radiation or other factors with a similar latitudinal and seasonal variation.
Institute of Clinical Medicine, University of Oslo, Norway.
Andreas
A
Lossius
Trond
T
Riise
Maura
M
Pugliatti
Kjetil
K
Bjørnevik
Ilaria
I
Casetta
Jelena
J
Drulovic
Enrico
E
Granieri
Margitta T
MT
Kampman
Anne-Marie
AM
Landtblom
Klaus
K
Lauer
Sandra
S
Magalhaes
Kjell-Morten
KM
Myhr
Tatjana
T
Pekmezovic
Kristin
K
Wesnes
Christina
C
Wolfson
Trygve
T
Holmøy
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D020031:Epstein-Barr Virus Infections / Q000821:virology*; D005260:Female; D006801:Humans; D007244:Infectious Mononucleosis / Q000150:complications / Q000453:epidemiology* / Q000821:virology; D007558:Italy; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000150:complications / Q000453:epidemiology* / Q000821:virology; D009664:Norway; D012306:Risk; D012621:Seasons; D014807:Vitamin D / Q000378:metabolism
D014807:Vitamin D
Epstein-Barr virus; Multiple sclerosis; interaction; latitude; seasons; vitamin D