Table 3.

Association between giardiasis and subsequent documentation of arthritis or joint pain within 6 months of giardiasis index date^*, stratified by sex and age, MarketScan commercial health insurance database, 2006–2010

	Unadjusted logistic regression		Adjusted logistic regression†
	RR	(95% CI)	RR	(95% CI)
Age, years
0–19	2·01	(1·40–2·88)	1·63	(1·12–2·38)
20–64	1·61	(1·32–1·95)	1·45	(1·19–1·77)
Sex
Male	1·73	(1·35–2·21)	1·57	(1·22–2·01)
Female	1·65	(1·30–2·09)	1·44	(1·12–1·84)

RR, Risk ratio; CI, confidence interval.

^*The earliest record where a patient was given the ICD-9 code for giardiasis was considered their index date. Matched, unexposed persons (non-giardiasis cohort) were assigned an index date.

^†Adjusted for variables that change the RR for giardiasis by >10% in preliminary logistic regression analyses; only healthcare utilization rate quartile met this criteria in both age and sex-stratified analyses.