Table 3.

Associations between gestational age at birth (1973–1994) and risk of hemorrhagic or ischemic stroke (1991–2015), Sweden.

			Unadjusted	Adjusted*
	Cases	Rate†	HR (95% CI)	HR (95% CI)	P
Hemorrhagic stroke
Preterm (<37 wks)	156	12.1	1.20 (1.02, 1.42)	1.15 (0.97, 1.35)	0.10
Early preterm (<34 wks)	40	15.0	1.51 (1.10, 2.06)	1.42 (1.04, 1.94)	0.03
Late preterm (34–36 wks)	116	11.3	1.13 (0.93, 1.36)	1.08 (0.89, 1.30)	0.44
Early term (37–38 wks)	469	10.5	1.05 (0.95, 1.17)	1.02 (0.92, 1.13)	0.73
Full-term (39–41 wks)	1,199	10.2	Reference	Reference
Post-term (≥42 wks)	319	10.8	1.00 (0.89, 1.13)	1.01 (0.90, 1.14)	0.83
Per additional week (trend)			0.96 (0.94, 0.99)	0.98 (0.96, 1.00)	0.07
Ischemic stroke
Preterm (<37 wks)	104	8.0	1.35 (1.11, 1.66)	1.31 (1.07, 1.60)	0.009
Early preterm (<34 wks)	22	8.2	1.40 (0.92, 2.14)	1.33 (0.87, 2.03)	0.18
Late preterm (34–36 wks)	82	8.0	1.34 (1.07, 1.68)	1.30 (1.04, 1.63)	0.02
Early term (37–38 wks)	271	6.0	1.04 (0.91, 1.19)	1.02 (0.89, 1.16)	0.78
Full-term (39–41 wks)	1,180	6.1	Reference	Reference
Post-term (≥42 wks)	174	5.9	0.89 (0.76, 1.04)	0.90 (0.76, 1.05)	0.18
Per additional week (trend)			0.96 (0.94, 0.99)	0.97 (0.94, 0.99)	0.01

^*Adjusted for child characteristics (age, sex, birth year, birth order), maternal characteristics (age, education, birth country or region, BMI, smoking, preeclampsia, other hypertensive disorders, diabetes), and paternal characteristics (age, education).

^†Incidence rate per 100,000 person-years.