African immigrants' favorable preterm birth rates challenge genetic etiology of the Black-White disparity in preterm birth.

Background: We examined over a million California birth records for 2010 through 2021 to investigate whether disparities in preterm birth (PTB) by nativity and race support the widely held but hitherto unsubstantiated belief that genetic differences explain the persistent Black-White disparity in PTB. Methods: We examined PTB rates and risk ratios among African-, Caribbean-, and U.S.-born Black women compared to U.S.-born White women. Multivariate analyses adjusted for maternal age, education, number of live births, delivery payer, trimester of prenatal care initiation, pre-pregnancy BMI, smoking, and prevalence of poverty in a woman's residence census tract; and for paternal education. Results: In adjusted analyses, African-born Black women's PTB rates were no different from those of U.S.-born White women. Discussion: The results add to prior evidence making a genetic etiology for the racial disparity in PTB unlikely. If genetic differences tied to "race" explained the Black-White disparity in PTB among U.S.-born women, the African immigrants in this study would have had higher rates of PTB, not the lower rates observed. Multiple explanations for the observed patterns and their implications are discussed. Failure to distinguish causes of PTB from causes of the racial disparity in PTB have likely contributed to erroneous attribution of the racial disparity to genetic differences. Based on the literature, unmeasured experiences of racism, including racism-related stress and adverse environmental exposures, are plausible explanations for the PTB disparity between Black and White U.S.-born women. The favorable birth outcomes of African-born Black immigrants may reflect less exposure to racism during sensitive life periods, e.g., childhood, when they were in African countries, where Black people are in the racial majority.

Interrelationships of physical activity in different domains: Evidence from the Geographic Research on Wellbeing (GROW) study.

Research has rarely distinguished between non-work (NW) and work (W) active transport (AT) or investigated relationships to other domains of physical activity ([PA], like leisure time [LTPA] or work [WPA]). We investigated correlates of AT by employment status, accounting for LTPA and WPA, in a population-based sample of California mothers (N=2906) in the Geographic Research on Wellbeing (GROW) study (2012-2013). AT was measured by the National Household Travel Survey. LTPA was measured using the Stanford Leisure-Time Activity Categorical Item. WPA was measured with the Stanford Brief Activity Survey. Most employed mothers (53%) worked in sedentary jobs, and few (<10%) used NWAT or WAT. Over 20% of unemployed mothers used NWAT, although LTPA levels were similar to employed mothers. Multiple regression models found employed and unemployed with low education and income, and unemployed African American or Latina immigrant mothers had higher odds of using NWAT. Younger employed and unemployed mothers, and unemployed who had ≥4 children or had "light" LTPA had lower odds of using NWAT. Multiple regression models demonstrated that low education or income employed mothers, African American mothers, those who worked part time, and those with relatively low LTPA had higher odds of using WAT, while younger women had lower odds of using WAT, compared with reference groups (ps<0.05). WPA was associated with WAT in unadjusted models, but not in adjusted models. Different AT patterns were seen for employed vs unemployed women, but women who used AT did so for most trips. LTPA was associated with NWAT among unemployed mothers and with WAT among employed mothers. Most women were underactive across all domains, suggesting no compensatory effect of PA done in one domain reducing PA done in another domain, with few meeting minimal guidelines. Policy and practice strategies should support infrastructure to encourage a variety of domains of PA.