Timing of pubertal stages and breast cancer risk: the Breakthrough Generations Study

Breast Cancer Research

Table 2 Risk of invasive or in situ breast cancer in relation to pubertal variables

	Adjusted for attained age			Multivariate-adjusted^a
Pubertal variable	Ncases/person-years	HR (95% CI)		Ncases/person-years	HR (95% CI)
Age at thelarche, years
≤10	152/53,916	1.22 (1.02,1.47)	*	151/53,308	1.23 (1.02, 1.48)	*
11 to 12	445/17,5791	Referent		443/173,413	Referent
≥13	276/120,309	0.82 (0.71,0.96)	*	269/118,581	0.80 (0.69, 0.93)	**
HR for trend		0.82 (0.74, 0.90)	***		0.81 (0.73, 0.89)	***
Age at menarche, years
≤12	451/171,139	1.03 (0.90,1.17)		449/168,478	1.06 (0.93,1.21)
13 to 14	449/171,466	Referent		444/168,733	Referent
≥15	86/38,779	0.81 (0.64,1.02)		83/38,109	0.78 (0.62,0.99)	*
HR for trend		0.92 (0.83, 1.01)			0.89 (0.81, 0.99)	*
Age at regular periods, years
≤12	213/80,631	0.97 (0.81,1.15)		212/79,450	0.99 (0.83,1.18)
13 to 14	295/107,008	Referent		292/105,314	Referent
≥15	105/50,215	0.74 (0.59,0.93)	**	104/49,465	0.74 (0.59,0.92)	**
Never had	73/26,114	1.15 (0.89,1.49)		73/25,581	1.16 (0.90,1.50)
regular periods	73/26,114	1.15 (0.89,1.49)		73/25,581	1.16 (0.90,1.50)
HR for trend^b		0.90 (0.81, 1.00)			0.88 (0.79, 0.98)	*
Age reached adult height, years
≤14	198/73,048	1.20 (0.99,1.45)		198/72,430	1.25 (1.03,1.52)	*
15 to 16	212/100,038	Referent		208/98,651	Referent
≥17	148/69,134	1.06 (0.86,1.31)		148/67,894	1.07 (0.87,1.32)
HR for trend		0.93 (0.84, 1.04)			0.92 (0.82, 1.02)
Growth spurt between ages 7 and 11 years^c
No	956/37,8071	Referent		947/372,171	Referent
Yes	100/34,784	1.15 (0.94,1.41)		98/34,259	1.12 (0.91,1.38)

CI ,Confidence interval; HR, Hazard ratio.
^*P <0.05; **P <0.01; ***P <0.001.
^aAdjusted for attained age, menopausal status, family history of breast cancer in a first-degree relative, adult height, age at first full-term pregnancy (with a term for nulliparous women) and HRT status.
^bTest for trend excludes those who had never had a regular period.
^cSubjects were classed as having had a growth spurt between ages 7 and 11 years if their height compared with girls of a similar age increased by at least one category from age 7 to 11.

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