Key Points
Question
Is the interaction between mammographic breast density and overweight or obesity associated with breast cancer risk, and if so, does any association vary according to menopausal status?
Findings
In a cohort study of 3 248 941 premenopausal and 4 373 473 postmenopausal women aged 40 years or older screened for breast cancer, a positive additive interaction between high breast density and high body mass index was associated with an increased risk of breast cancer, especially among women in the postmenopausal period.
Meaning
This study suggests that women with overweight or obesity and dense breast tissue might benefit from tailored breast cancer screening strategies; these 2 factors should be incorporated into risk stratification in population-based breast cancer screening.
Breast density is strongly associated with breast cancer risk; however, studies on the association between density changes and breast cancer risk have controversial results. The aim of our study was to determine the association between breast density changes and breast cancer risk in East‐Asian women. We included 3 301 279 women aged ≥40 years screened for breast cancer twice during 2009 to 2010 and 2011 to 2012. Data were obtained from the National Health Insurance Service (NHIS) database. Breast density was evaluated using the Breast Imaging‐Reporting and Data System (BI‐RADS). Relative risk (RR) and 5‐year risk of developing breast cancer according to density category changes were calculated. Overall, 23.0% of the women had a higher breast density and 22.2% of the women had a lower breast density in second screening compared to the first. An increase in the BI‐RADS density category between two subsequent mammographic screenings was associated with an increase in breast cancer risk and vice versa in terms of RR. The 5‐year breast cancer risk was affected by the initial BI‐RADS density category, changes in density category and patients' characteristics such as age, menopausal status and family history of breast cancer. In patients with breast cancer family history, the 5‐year breast cancer risk was prominent, at a maximum of 2.39% (95% CI = 1.23‐3.55) in women with breast density category of 2 to 4. Changes in the BI‐RADS density category were associated with breast cancer risk. Longitudinal measures of BI‐RADS density may be helpful in identifying high‐risk women, especially those with a breast cancer family history.
OBJECTIVES:To examine how the trends in the weekly frequencies of gastrointestinal infectious diseases changed before and during the COVID-19 pandemic in Korea, and to compare them with the trends in the United States.
METHODS:We compared the weekly frequencies of gastrointestinal infectious diseases (16 bacterial and 6 viral diseases) in Korea during weeks 5-52 before and after COVID-19. In addition, the weekly frequencies of five gastrointestinal infectious diseases in the United States (data from the Centers for Disease Control and Prevention) that overlapped with those in Korea were compared.
RESULTS:The mean weekly number of total gastrointestinal infectious diseases in Korea showed a significant decrease (from 522 before COVID-19 to 245 after COVID-19, P < 0.01).
Only bacterial gastrointestinal infectious diseases caused byCampylobacter increased significantly; other bacterial gastrointestinal infectious diseases showed either a decrease or no change. All other viral diseases decreased. In the United States, the weekly numbers of Salmonella, Campylobacter, typhoid, shigellosis, and hepatitis A virus sharply decreased after the COVID-19 outbreak. The weekly numbers of all viral diseases markedly decreased in both countries; however, the bacterial gastrointestinal infectious diseases showed a different pattern. CONCLUSIONS: Most gastrointestinal infectious diseases decreased after the COVID-19 outbreak. In contrast, Campylobacter infections showed an increasing trend in Korea, but a decreasing trend in the United States. Further studies are needed to elucidate the different trends in bacterial and viral infectious diseases before and after NPIs and between different countries.
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