Table II.

History of severe teenage acne and risk of laparoscopically confirmed endometriosis in the NHS II cohort, 1989–2009.

	No acne	Acne
Number of cases/person-year	3951/1 044 018	431/88 254
Age-adjusted RR	1.00	1.29 (1.17–1.42)
MV RRa	1.00	1.20 (1.08–1.32)
MV1: MV plus infertility	1.00	1.20 (1.08, 1.33)
MV2: MV1 plus skin and hair characteristicsb	1.00	1.19 (1.08, 1.32)
MV3: MV2 plus selected medicationsc	1.00	1.18 (1.07, 1.31)

^aAdjusted by age, BMI (<18.5, 18.5–22.4, 22.5–24.9, 25.0–29.9, 30.0–34.9, 35.0–39.9 and 40+), BMI at age 18 (<18.5, 18.5–22.4, 22.5–24.9, 25.0–29.9, 30.0–34.9, 35.0–39.9 and 40+), age of menarche (≤11, 12–13 and 14+ years), parity (nulliparous, 1 pregnancies >6 months, 2 pregnancies >6 months, 3 pregnancies >6 months and 4+ pregnancies >6 months), menstrual cycle length at ages 18–22 (<21, 21–25, 26–31, 32–39 and 40+ days), oral contraceptive use (never, current and past), smoking status (never, past and current), height (<1.60, 1.60–1.65 and 1.70+), age at first birth (<25, 25–29 and 30+), ibuprofen use (yes, no), alcohol drinking at ages 15–17 (non-drinker, 1–3/month, 1/week, 2–4/week, 5–6/week and 7+/week) and ancestry (Caucasian, African American, Hispanic, Asian and others).

^bNumber of sunburns, childhood skin's reaction to sun (no reaction, some redness only, burn, painful burn, burn with blistering), and natural hair colour (red, blonde, light brown, dark brown, and black).

^cTetracycline use for >5 years (collected in 1993), isotretinoin use (never, ever).