Table 3. Co-sibling analyses for gestational age at birth in relation to risk of lipid disorders, Sweden, 1973–2016.

Gestational age at birth	Cases	Ratea'	Adjusted for shared familial factorsb		Additionally adjusted for child and maternal characteristicsc
			HR (95% CI)	P	HR (95% CI)	P
Preterm (<37 wks)	1,006	93.86	1.14 (1.01–1.28)	0.03	1.10 (0.97–1.24)	0.13
Extremely preterm (22–27 wks)	19	123.62	1.61 (0.75–3.45)	0.22	1.46 (0.68–3.15)	0.33
Very preterm (28–33 wks)	203	101.91	1.15 (0.90–1.48)	0.25	1.09 (0.85–1.40)	0.49
Late preterm (34–36 wks)	784	91.45	1.12 (0.99–1.28)	0.08	1.09 (0.96–1.24)	0.19
Early term (37–38 wks)	3,077	78.97	1.10 (1.03–1.18)	0.005	1.06 (0.98–1.13)	0.13
Full term (39–41 wks)	12,413	74.31	Reference		Reference
Post term (≥42 wks)	2,004	82.57	0.97 (0.89–1.05)	0.41	1.02 (0.93–1.11)	0.69
Per additional 5 weeks (trend)			0.86 (0.80–0.93)	<0.001	0.93 (0.86–1.00)	0.05

^aIncidence rate per 100,000 person-years.

^bAdjusted for shared familial (genetic and/or environmental) factors.

^cAdditionally adjusted for specific child characteristics (birth year, sex, birth order) and maternal characteristics (age, education, birth country or region, body mass index, history of lipid disorder).

Abbreviations: HR, hazard ratio