The association between farming activities, precipitation, and the risk of acute gastrointestinal illness in rural municipalities of Quebec, Canada: a cross-sectional study

Table 7 Modification effect of season on association between acute gastrointestinal illness (AGI) and cumulative precipitation three and four weeks prior to the onset of AGI in Quebec rural municipalities, Canada, April 2007-April 2008

Week*	W.n†	Precipitation	OR‡ (95% CI) p-value for OR			p§
			Spring	Summer	Fall
3 (days 15-21)	4770	High	0.83 (027-2.53) 0.749	0.71 (0.28-1.78) 0.457	2.20 (1.09-4.44) 0.028	0.162
		Moderate	1.16 (0.65-2.06) 0.618	1.32 (0.72-2.41) 0.361	0.84 (0.43-1.65) 0.614
		Low¶	1.00	1.00	1.00
		Very low	0.49 (0.23-1.03) 0.059	0.72 (0.24-2.18) 0.566	0.46 (0.14-1.46) 0.186
4 (days 22-28)	4771	High	0.75 (0.34-1.98) 0.829	0.92 (0.43-1.98) 0.829	2.03 (0.95-4.34) 0.068	0.026
		Moderate	1.32 (0.77-2.27) 0.305	1.37 (0.70-2.67) 0.356	0.62 (0.31-1.24) 0.180
		Low¶	1.00	1.00	1.00
		Very low	0.94 (0.39-2.28) 0.890	2.19 (1.02-4.71) 0.044	0.72 (0.24-2.14) 0.553

* Each one-week-period [prior to the onset of AGI (for cases) or the interview date (for non-cases)] was modelled separately.
† Weighted n, weighted by age and sex to the population of the study area, according to the data from the 2006 Canadian census of population.
‡ Odds ratio for the precipitation presented according to season. The odds ratio was adjusted for other risk factors. Winter season was excluded for the analysis because of very cold winters in Quebec, with precipitation taking mostly the form of snow during that season.
§ p-value for interaction term between precipitation and season.
¶ Reference

ISSN: 1471-2458