Table 2.

HRs (95% CIs) for the association between time-varying exposure to air pollutants (per 5-unit increase) and incident ovarian cancer in the Sister Study ($n=\mathrm{40,308}$, enrolled 2003–2009).

Overall models, subgroups	Casesa	Person-years	${\mathrm{NO}}_2$ (ppb)b	${\mathrm{PM}}_{2.5}$ (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)b	${\mathrm{O}}_3$ (ppb)b
			HR (95% CI)	HR (95% CI)	HR (95% CI)
Overall
Model 1c	249	395,950	1.21 (1.04, 1.41)	1.31 (0.90, 1.91)	0.92 (0.77, 1.09)
Model 2d	249	395,950	1.21 (0.99, 1.47)	1.02 (0.65, 1.60)	1.00 (0.82, 1.22)
Model 3e	247	391,673	1.17 (0.95, 1.43)	1.00 (0.64, 1.58)	1.00 (0.82, 1.22)
Confirmed casesc,f	205	395,950	1.14 (0.96, 1.35)	0.99 (0.60, 1.63)g	0.89 (0.73, 1.07)
Menopausal statusc,h
Premenopausal	43	101,436	1.14 (0.80, 1.62)	2.85 (0.98, 8.29)g	1.36 (0.88, 2.10)
Postmenopausal	206	294,515	1.20 (1.02, 1.42)	0.81 (0.49, 1.33)g	0.85 (0.70, 1.03)
$p_{\text{heterogeneity}}$			0.95	0.16	0.09
US Census regionc,h
Northeast	40	70,279	1.17 (0.88, 1.55)	0.56 (0.13, 2.34)g	0.79 (0.44, 1.44)
Midwest	71	107,060	1.61 (1.12, 2.32)	1.40 (0.40, 4.89)g	0.68 (0.42, 1.10)
South	78	131,080	1.20 (0.77, 1.87)	0.59 (0.23, 1.52)g	1.05 (0.64, 1.71)
West	60	87,531	1.10 (0.84, 1.44)	1.63 (0.75, 3.52)g	0.98 (0.78, 1.24)
$p_{\text{heterogeneity}}$			0.68	0.15	0.45
Urbanicityc,h
Urban	39	74,811	1.44 (1.02, 2.02)	1.29 (0.47, 3.58)g	0.69 (0.42, 1.12)
Suburban	98	160,993	1.25 (0.93, 1.69)	1.15 (0.52, 2.54)g	0.93 (0.66, 1.30)
Rural/small town/other	112	160,146	1.42 (1.05, 1.91)	0.95 (0.48, 1.87)g	0.95 (0.73, 1.23)
$p_{\text{heterogeneity}}$			0.57	0.57	0.78

Note: CI, confidence interval; HR, hazard ratio; ${\mathrm{NO}}_2$, nitrogen dioxide; nSES, neighborhood socioeconomic status score; ${\mathrm{O}}_3$, ozone; ${\mathrm{PM}}_{2.5}$, particulate matter $<2.5\mathrm{\mu }\mathrm{m}$ in diameter.

^a Participants were considered at risk from enrollment to ovarian cancer diagnosis with censoring at the earliest of bilateral oophorectomy, loss to follow-up, death, or the administrative end of follow-up (June 2017).

^b Spearman’s rank correlation coefficients: ${\mathrm{NO}}_2$ and ${\mathrm{PM}}_{2.5}=0.35$, ${\mathrm{NO}}_2$ and ${\mathrm{O}}_3=-0.61$, and ${\mathrm{PM}}_{2.5}$ and ${\mathrm{O}}_3=-0.20$.

^c Cox proportional hazards model adjusted for calendar month (time scale), age (strata), race/ethnicity [Black, Hispanic/Latina, non-Hispanic White, other (including American Indian/Alaskan Native, Asian, Native Hawaiian or other Pacific Islander)], education (high school or less, some college, college degree or higher), baseline nSES (an index developed using 16 tract-level measures of educational attainment, occupation, income, wealth, poverty, employment status, and housing characteristics from the US Census and American Community Survey, with higher index indicating lower nSES and vice versa), and time-varying US Census region (Northeast, Midwest, South, West).

^d In addition to covariates included in model 1, model 2 was mutually adjusted for time-varying copollutants (e.g., models for ${\mathrm{NO}}_2$ were adjusted for ${\mathrm{PM}}_{2.5}$ and ${\mathrm{O}}_3$).

^e In addition to covariates included in models 1 and 2, model 3 was adjusted for ovarian risk factors, including smoking (never, former, current), alcohol consumption (none, $<1$, $1\text{\hspace{0.17em}to}<7$, $\ge 7$ drinks per week), physical activity ($<5$, $5\text{\hspace{0.17em}to}<10$, $10\text{\hspace{0.17em}to}<20$, $\ge 20$ metabolic equivalent hours per week), body mass index ($<25$, $25\text{\hspace{0.17em}to}<30$, $\ge 30{\mathrm{kg}/\mathrm{m}}^2$), age at first birth (nulliparous, $<20$, $20\text{\hspace{0.17em}to}<25$, $\ge 25\mathrm{y}$), parity (nulliparous, 1–2, $\ge 3$ births), breastfeeding (nulliparous, $<1$, $1\text{\hspace{0.17em}to}<7$, $\ge 7\text{\hspace{0.17em}months}$), oral contraceptive use (never, ever), age at menopause (premenopausal, $<50$, $50\text{\hspace{0.17em}to}<55$, $\ge 55\mathrm{y}$), age at menarche ($<12$, 12–13, $\ge 14\mathrm{y}$), postmenopausal hormone therapy use (never, former, current), and mother or sister with a ovarian cancer diagnosis (yes, no).

^f Restricted to cases confirmed by medical records; the confirmed cases include 108 serous, 14 endometrioid, 9 mucinous, and 9 clear cell carcinoma, as well as 29 other subtypes.

^g For ${\mathrm{PM}}_{2.5}$ analyses, models were additionally adjusted for time-varying ${\mathrm{NO}}_2$ and ${\mathrm{O}}_3$ levels, due to estimate changes observed after adjusting for these copollutants.

^h Stratum-specific HRs were estimated by augmenting the primary model with multiplicative interaction terms and tested for heterogeneity using likelihood ratio tests.