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Gli studi di coorte - Centro per lo Studio e la Prevenzione ...

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Rischio <strong>di</strong> t. mammel<strong>la</strong> e contraccettivi orali – Nurses’ Health Study*<br />

Oral contraceptive use<br />

Yes<br />

NO Total<br />

(current or past use)<br />

Cases<br />

204<br />

240<br />

444<br />

Person-years at risk<br />

94 029<br />

128 528<br />

222 557<br />

Rate (x100 000)<br />

217<br />

187<br />

199<br />

Rate Ratio = 217 <strong>per</strong> 100 000 pyrs/187 <strong>per</strong> 100.000pyrs= 1.16<br />

Rate Difference = 217 <strong>per</strong> 100 000 pyrs – 187 <strong>per</strong> 100 000 pyrs = 30 <strong>per</strong> 100 000 pyrs<br />

* Data from Romieu et al, 1989<br />

Mo<strong>di</strong>ficato da dos Santos Silva IARC, 1999

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