Lack of association between the MTHFR C677T variant and migraine with aura in an older population: Could selective survival play a role?

Ann I. Scher*, Gudny Eiriksdottir, Melissa Garcia, Preethy Feit, Albert V. Smith, Tamara B. Harris, Kathryn A. Roecklein, Larus S. Gudmundsson, Vilmundur Gudnason, Lenore J. Launer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Background: Several studies, but not all, of primarily middle-aged or younger adults have suggested that the common MTHFR C677T variant is a genetic risk factor for migraine with aura (MA). Here, we consider whether this variant is associated with MA risk in an older non-clinical population (AGES-Reykjavik cohort). Methods: Participants are a sub-sample (n=1976) of subjects from the Reykjavik Study (RS; mean age 50) and its continuation, AGES-RS (mean age 76).We estimated the relative odds of MA in TT versus CC carriers using multinomial logistic regression. As both MA and the TT genotype may be linked with modestly reduced longevity, we performed a simple simulation to illustrate the effect that selective survival may have had on our observed genedisease association. Results: TT versus CC carriers were at marginally reduced odds of MA (ORTT 0.55 (0.31.0), p=0.07), significantly for women (ORTT 0.45 (0.20.9), p=0.03). Assuming the true (e.g. mid-life) effect of the TT genotype is OR TT 1.26, from a recent meta-analysis, our simulation suggested that if 25-year mortality had been (hypothetically) 13% higher in MA subjects with the TT versus CC genotype, the measured effect of the TT genotype on MA would have been attenuated to non-significance (e.g. ORTT 1.00). Our observed protective effect was consistent with the most extreme selective mortality scenario, in which essentially all of the previously reported increased mortality in MA subjects was (hypothetically) found in CT or TT carriers. Conclusion: The MTHFR 677TT genotype was associated with marginally reduced risk of MA in our older population. Our simulation illustrated how even modest selective survival might obscure the apparent effect of a genetic or other risk factor in older populations. We speculate that some of the heterogeneity previously observed for this particular genetic variant may be due to age range differences in the studied populations.

Original languageEnglish
Pages (from-to)308-315
Number of pages8
Issue number5
StatePublished - Apr 2013
Externally publishedYes


  • Migraine
  • association studies in genetics
  • folate
  • selection bias
  • selective survival


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