Multiparity and the risk of premenopausal breast cancer: different effects across ethnic groups in Singapore

Background The relationship between multiparity and premenopausal breast cancer risk is different in Caucasian, African-American and Hispanic women. For Asian women, this relationship has never been well studied. Methods Within the Singapore Birth Registry, we selected all women who had a first child between 1986 and 2002 (169,936 Chinese, 40,521 Malay, 17,966 Indian). We linked them to the Singapore Cancer Registry data to identify those who developed breast cancer after childbirth (n=527). We used multivariate Cox analysis to examine the relationship between parity, ethnicity and premenopausal breast cancer risk. Results Compared to Chinese, Malay women had increased and Indian women had decreased risks of premenopausal breast cancer (adjusted Hazard Ratios [HRadj] 1.25 [1.0-1.6] and 0.48 [0.3-0.8] respectively). Multiparity did not modify the risk of premenopausal breast cancer in Chinese and Indians. In Malays there was a significant risk reduction with increasing parity (P trend 0.037). Malay women with one, two and ≥3 children had premenopausal breast cancer risks (HRadj) of 1.86 (1.2-3.0), 1.52 (1.1-2.2) and 0.87 (0.6-1.3) respectively compared to their Chinese counterparts. Conclusions The impact of multiparity on premenopausal breast cancer risk differs across ethnic groups in Singapore. Increasing parity reduces the risk of premenopausal breast cancer in Malay, but not in Chinese and Indian women. Uniparous Malay women have twice the risk of premenopausal breast cancer compared to uniparous Chinese. This excess risk disappears after giving birth to ≥3 children. Indian women have lower premenopausal breast cancer risks than Chinese, regardless of their parity statu

Gender, ethnicity, health behaviour & self-rated health in Singapore

10.1186/1471-2458-7-184BMC Public Health718

Multiparity and the risk of premenopausal breast cancer: Different effects across ethnic groups in Singapore

10.1007/s10549-008-9947-yBreast Cancer Research and Treatment1133553-55

Daily testing for contacts of individuals with SARS-CoV-2 infection and attendance and SARS-CoV-2 transmission in English secondary schools and colleges: an open-label, cluster-randomised trial

Background: School-based COVID-19 contacts in England are asked to self-isolate at home, missing key educational opportunities. We trialled daily testing of contacts as an alternative to test if this resulted in similar control of transmission, while allowing more school attendance.Methods: We performed an open-label cluster-randomised controlled trial in secondary schools and further education colleges in England (ISRCTN18100261). Schools were randomised to self-isolation of school-based COVID-19 contacts for 10 days (control) or to voluntary daily lateral flow device (LFD) testing with LFD-negative contacts remaining at school (intervention).Co-primary outcomes in all students and staff were symptomatic PCR-confirmed COVID-19, adjusted for community case rates, to estimate within-school transmission (non-inferiority margin: <50% relative increase), and COVID-19-related school absence. Analyses were performed on an intention to treat (ITT) basis using quasi-Poisson regression, also estimating complier average causal effects (CACE). Secondary outcomes included participation rates, PCR results in contacts and performance characteristics of LFDs vs. PCR.Findings: Of 99 control and 102 intervention schools, 76 and 86 actively participated (19-April-2021 to 27-June-2021); additional national data allowed most non-participating schools to be included in co-primary outcomes. 2432/5763(42.4%) intervention arm contacts participated. There were 657 symptomatic PCR-confirmed infections during 7,782,537 days-at-risk (59.1/100k/week) and 740 during 8,379,749 days-at-risk (61.8/100k/week) in the control and intervention arms respectively (ITT-adjusted incidence rate ratio, aIRR=0.96[95%CI 0.75-1.22;p=0.72]) (CACE-aIRR=0.86[0.55-1.34]). There were 55,718 COVID-related absences during 3,092,515 person-school-days(1.8%) and 48,609 during 3,305,403 person-school-days(1.5%) in the control and intervention arms (ITT-aIRR=0.80[95%CI 0.53-1.21;p=0.29]) (CACE-aIRR 0.61[0.30-1.23]). 14/886(1.6%) control contacts providing an asymptomatic PCR sample tested positive compared to 44/2981(1.5%) intervention contacts (adjusted odds ratio, aOR=0.73[95%CI 0.33-1.61;p=0.44]); rates of symptomatic infection in contacts were 44/4665(0.9%) and 79/5955(1.3%), respectively (aOR=1.21[0.82-1.79;p=0.34]). Interpretation: Daily contact testing of school-based contacts was non-inferior to self-isolation for control of COVID-19 transmission, with similar rates of student and staff symptomatic infections with both approaches. Infection rates in school-based contacts were only around 2%. Daily contact testing should be considered for implementation as a safe alternative to home isolation following school-based exposures