To determine whether an association exists between weather variables and headache in people with episodic migraine (EM) and if long-term fremanezumab treatment modifies this association.

Data on the effects of preventive migraine treatments on weather-triggered headaches are limited.

This post hoc analysis included daily headache diary data from participants from across the United States enrolled in HALO-EM, a 28-week, double-blind, placebo-controlled, Phase 3 study of fremanezumab for the prevention of EM, and/or HALO-LTS, a 12-month study that included HALO-EM completers and new participants, with hourly measurements of weather variables from the National Climatic Data Center. Primary outcome measures: any-onset headache (AOH) days (any day with headache) and new-onset headache (NOH) days (headache on a given day with no headache the preceding day). A general, linear, mixed-effects model was used to explore the association between weather variables and AOH and NOH days among all participants during non-fremanezumab and fremanezumab treatment periods. These associations were then compared between treatment periods.

In total, 748 participants (101,963 daily diary records) were included: female, 85.8%; mean age, 41.9 years; concomitant preventive treatment use, 19.5%. A daily average temperature increase of 10 F significantly increased the risk of having an AOH day at baseline, and an AOH or NOH day during the placebo period, and after the first month of fremanezumab treatment (odds ratios [ORs]: 1.07–1.08, all p<0.001); this increased risk was not significant for a NOH day at baseline (OR: 1.05, p=0.09). After 3 months and ≥6 months of fremanezumab treatment, the ORs for a AOH or NOH day reduced to 1.02–1.04 and 1.00, respectively, and were no longer statistically significant.

Fremanezumab attenuated the association between a 10 F increase in temperature and AOH or NOH days, suggesting that long-term fremanezumab treatment may prevent temperature-triggered headaches in people with EM.