Table 5.

Associations between hours of swimming pool use and bladder cancer, New England Bladder Cancer Study, 2001–2004.

Exposure metric	Cases ($n=\mathrm{1,193}$)	Controls ($n=\mathrm{1,414}$)	OR	95% CI
Total hours during any time period
Never used swimming pool	653	743	1.00
0–1,000	151	168	1.04	0.80, 1.36
$>\mathrm{1,000}–\mathrm{2,316}$	149	168	1.11	0.85, 1.45
$>\mathrm{2,316}–\mathrm{4,824}$	137	168	0.96	0.73, 1.26
$>\mathrm{4,824}–\mathrm{8,684}$	57	100	0.67	0.48, 1.00
$>\mathrm{8,684}–\mathrm{12,174}$	15	34	0.55	0.28, 1.05
$>\mathrm{12,174}$	31	33	0.94	0.55, 1.59
			$p-\text{trend}=0.09$
Total hours during summer
Never used swimming pool	653	743	1.00
0–480	123	175	0.86	0.65, 1.13
$>480–\mathrm{1,140}$	145	161	1.10	0.84, 1.44
$>\mathrm{1,140}–\mathrm{3,000}$	161	179	1.11	0.85, 1.43
$>\mathrm{3,000}–\mathrm{4,956}$	57	89	0.65	0.44, 0.95
$>\mathrm{4,956}–\mathrm{6,660}$	31	34	1.06	0.61, 1.81
$>\mathrm{6,660}$	23	33	0.82	0.46, 1.47
			$p-\text{trend}=0.33$
Total hours not during summer
Never used swimming pool	653	743	1.00
0 h not in summer	285	314	1.09	0.88, 1.35
$>0–600$	25	37	0.65	0.37, 1.14
$>600–\mathrm{2,280}$	134	171	0.92	0.70, 1.21
$>\mathrm{2,280}–\mathrm{5,320}$	55	94	0.81	0.55, 1.18
$>\mathrm{5,320}–\mathrm{7,720}$	15	25	0.73	0.37, 1.44
$>\mathrm{7,720}$	26	33	0.85	0.49, 1.48
			$p-\text{trend}=0.16$

Note: Adjusted for age ($<55$, 55–64, 65–74 and 75–79 y), ethnicity (Hispanic/non-Hispanic), race (white only, mixed race, other race), smoking status (never, occasional, former, current, state of residence (Maine, New Hampshire, Vermont), ever employment in a high-risk occupation, and average trihalomethane concentration ($<5.55\mathrm{mg}/\mathrm{L}$, $5.55\text{to}<14.47\mathrm{mg}/\mathrm{L}$, $14.47\text{to}<26.39\mathrm{mg}/\mathrm{L}$, $26.39\text{to}<37.78\mathrm{\mu }\mathrm{g}/\mathrm{L}$, $37.38\text{to}<47.99\mathrm{\mu }\mathrm{g}/\mathrm{L}$, $>47.99\mathrm{mg}/\mathrm{L}$). Trend tests based on the midpoint of the category treated as a continuous variable. CI, confidence interval; OR, odds ratio.