The log transformed larval recovery data were analyzed for effect of day, stratum, and day × stratum interaction for each grass species during two separate experimental periods.
Each case was matched to 7 control days on the same day of the week during the 56-day stratum.
First, we compared the association between temperature and suicide adjusting for month and date with the unadjusted association for temperature based on 28- and 56-day strata in national capital cities (Seoul, Tokyo, and Taipei) to examine whether a 56-day stratum was appropriate.
We used 28-day strata, and compared cases with referent times 7, 14, and 21 days before or after the case, within the same stratum.
We conducted a sensitivity analyses to determine whether the basic model results were robust to the selection of controls, comparing the aforementioned design that sampled referent times +/- 7, 14, and 21 days within 28-day strata, to a design with referent times +/- 7 and 14 days within 21-day strata.
Finally, we determined the average amount of excess (flu-attributable) mortality during flu season by fitting a Poisson regression model to data on 39,420 person-day strata (12 age-sex groups × 9 years × 365 calendar days, combining the 2 extra leap days with February 28).
In our sensitivity analyses, the difference in the risk estimates between the 28- and 56-day strata was smaller in the model that adjusted for month and date than the difference in those in the model that did not adjust for the two variables.
Change scores were modeled via ANOVA for all couplets and for 3 average headache-day frequency strata: low (0-4 days/moderatemoderate (5-9 dand/monthighand high frequency episodic/chronic migraine ([HFEM/CM]≥10 days/month).
We selected every third day within the stratum of the case event as referents of the event to decrease serial correlation and excluded referents within seven days before and after the case event because we used up to seven day-moving averages of ozone as exposure indices and the accumulative effects of ozone effect might offset estimations.
Control days were defined as the same day of the same stratum as the case day.
