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Table 1 Baseline characteristics of study participants in the Breakthrough Generations Study recruited 2003–2012

From: Psychological stress, adverse life events and breast cancer incidence: a cohort investigation in 106,000 women in the United Kingdom

Characteristic Mean or No. SD or %
Age at recruitment, years 46.6 13.5
Average person-time, years 6.1 1.0
Menopausal status
 Postmenopausal 41,735 39.1
 Premenopausal 59,627 55.9
 Status not known 5216 5.0
 Never had periods 34 0.0
First-degree family history of breast cancer
 No 90,061 84.5
 Yes 16,551 15.5
Age at first full-term pregnancy, years
 ≤24 25,982 24.4
 25 to 34 46,690 43.8
 ≥35 4365 4.1
Parous, unknown age 166 0.2
Nulliparous 29,244 27.4
Parity not stated 165 0.2
Ethnicity
 White 105,313 98.8
 Other 1299 1.2
Socio-economic status based on place of residence
 1 (highest) 48,632 45.6
 2 12,200 11.4
 3 30,327 28.4
 4 8522 8.0
 5 (lowest) 6109 5.7
 No classificationa 822 0.8
Marital status
 Single 13,102 12.3
 Married/cohabiting 81,282 76.3
 Separated/divorced 8098 7.6
 Widowed 3631 3.4
 Other or not known 499 0.4
 Total 106,612 100.0
  1. a507 because they were resident in the Channel Islands, 315 for other reasons