Leisure-time physical activity, sedentary behavior, and risk of breast cancer: Results from the SUN ('Seguimiento Universidad De Navarra') project
R Sanchez-Bayona 1 , I Gardeazabal 2 , A Romanos-Nanclares 3 , C I Fernandez-Lazaro 3 , I Alvarez-Alvarez 4 , M Ruiz-Canela 3 , A Gea 5 , M A Martinez-Gonzalez 6 , M Santisteban 7 , E Toledo 8
Evidence is still limited on the influence of sedentary lifestyles on breast cancer (BC) risk. Also, prospective information on the combined effects of both sedentariness and leisure-time physical activity (LTPA) is scarce.
We aimed to assess the association of higher sedentary behavior and LTPA (separately and in combination) with the risk of BC in a middle-aged cohort of university graduates.
The SUN Project is a follow-up study initiated in 1999 with recruitment permanently open. Baseline assessments included a validated questionnaire on LTPA and sedentary habits. Subsequently, participants completed biennial follow-up questionnaires. Multivariable-adjusted Cox models were used to estimate the hazard ratios (HR) for incident BC according to LTPA, TV-watching, the joint classification of both, and a combined 8-item multidimensional active lifestyle score.
We included 10,812 women, with 11.8 years of median follow-up of. Among 115,802 women-years of follow-up, we confirmed 101 incident cases of BC. Women in the highest category of LTPA (>16.5 MET/h-week) showed a significantly lower risk of BC (HR = 0.55; 95% CI: 0.34-0.90) compared to women in the lowest category (≤6 MET/h-week). Women watching >2 h/d of TV exhibited a higher risk (HR = 1.67; 95% CI:1.03-2.72) than those who watched TV <1 h/d.
Women in the highest category (6-8 points) of the multidimensional combined 8-item score showed a lower BC risk (HR = 0.35; 95% CI: 0.15-0.79) than those in the lowest category (<2 points) group. There was no significant supra-multiplicative interaction between TV-watching and LTPA. Both low LTPA and TV-watching >2 h/d may substantially increase BC risk, independently of each other.
CITATION Prev Med. 2021 Jul;148:106535. doi: 10.1016/j.ypmed.2021.106535. Epub 2021 Mar 30.