Recreational physical activity and risk of triple negative breast cancer in the California Teachers Study

Table 6 Adjusted hazard ratios for the associations between changes in strenuous recreational physical activity levels and invasive breast cancer

RPA at baseline^a, h/wk/y	RPA at 10-year follow-up^b, h/wk/y	Overall	Observed person-years	Cases, no.	Adjusted HR (95 % CI)
Breast cancer overall
No change
Low (≤0.50)	Low (≤0.50)	24,028	396,185	692	Referent
Intermediate (0.51–3.50)	Intermediate (0.51–3.50)	6273	104,479	155	1.01 (0.84–1.21)
High (≥3.51)	High (≥3.51)	2462	41,105	42	0.71 (0.52–0.98)
Increasing
Low (≤0.50)	Intermediate (0.51–3.50)	5640	93,840	127	0.86 (0.71–1.04)
Low (≤0.50)	High (≥3.51)	1267	21,076	34	1.03 (0.72–1.45)
Intermediate (0.51–3.50)	High (≥3.51)	1751	29,121	40	0.89 (0.64–1.23)
Decreasing
Intermediate (0.51–3.50)	Low (≤0.50)	8436	139,718	209	0.96 (0.82–1.12)
High (≥3.51)	Low (≤0.50)	2212	36,515	58	1.00 (0.76–1.32)
High (≥3.51)	Intermediate (0.51–3.50)	2617	43,519	46	0.75 (0.55–1.02)

Results are for 54,686 women who completed baseline and 10-year follow-up questionnaires regarding RPA in recent 3 years in the California Teachers Study, 1995–2012. HRs are from multivariable Cox proportional hazards regression models using age (in days) as the time metric and stratified by age (in years) with the adjustment for race, family history of breast cancer in first-degree relatives, combined age at first full-term pregnancy and parity variable, combined menopausal status and MHT use variable, BMI at baseline, history of smoking, alcohol intake during the past year of baseline, screening mammogram in the past 2 years of baseline, history of a breast biopsy, and a corresponding changes in level of moderate RPA variable
Abbreviations: BMI body mass index, CI confidence interval, HR hazard ratio, h/wk/y hour/week/year, MHT menopausal hormone therapy, RPA recreational physical activity
^aRPA during the 3 years prior to baseline
^bRPA during the 3 years prior to 10-year follow-up