Association of sickle cell trait with adverse pregnancy outcomes in a population-based cohort.

INTRODUCTION: Sickle cell trait (SCT) is common in African descendants. Its association with several adverse pregnancy outcomes (APOs) has been reported but remains inconsistent. The objectives of this study are to test associations of SCT with APOs in non-Hispanic Black women, including (1) validate the associations of SCT with previously reported APOs, (2) test novel associations of SCT with broad spectrum of APOs, and (3) estimate the attributable risk of SCT for implicated APOs. MATERIAL AND METHODS: This is a retrospective analysis of a prospectively designed population-based cohort. Women/participants were self-reported non-Hispanic Black women from the UK Biobank (UKB). SCT status was determined based on heterozygous Glu6Val in the HBB gene. Several APOs were studied, including four previously reported SCT-associated APOs (preeclampsia, bacteriuria, pregnancy loss, and preterm delivery), and broad conditions related to pregnancy, childbirth, and the puerperium. APOs were curated by experts' peer review and consensus processes. Associations of SCT with APOs were tested by estimating its relative risk and 95% confidence interval (95% CI), adjusting for number of live births and age at first birth. Attributable risk proportion (ARP) and population attributable risk proportion (PARP) of SCT to APOs were estimated. RESULTS: Among the 4057 self-reported non-Hispanic Black women with pregnancy records in the UKB, 581 (14.32%) were SCT carriers. For four previously reported SCT-associated APOs, two were confirmed at a nominal P < 0.05; relative risk (RR) was 2.39 (95% CI 1.09-5.23) for preeclampsia, and 4.85 (95% CI 1.77-13.27) for bacteriuria. SCT contributed substantially to these two APOs among SCT carriers, with attributable risk proportion estimated at 61.00% and 68.96% for preeclampsia and bacteriuria, respectively. SCT also contributed substantially to these two APOs in the population (self-reported Black UK women), with population attributable risk proportion estimated at 18.30% and 24.14% for preeclampsia and bacteriuria, respectively. In addition, novel associations were found for seven other APOs (nominal P < 0.05). CONCLUSIONS: SCT is significantly associated with APOs in this study and contributes substantially to APOs among self-reported Black women in the UK. Confirmation of these findings in independent study populations is required.

Sickle Cell Trait and Risk for Common Diseases: Evidence from the UK Biobank.

BACKGROUND: Sickle cell trait is typically considered benign. Although evidence remains inconsistent, recent studies suggest that it is associated with several common diseases. We systematically assessed associations of sickle cell trait with reported diseases in a large population-based cohort. METHODS: Study subjects were self-reported Blacks from the UK Biobank (UKB), a United Kingdom population-based cohort of subjects aged 40-69 years at recruitment in the United Kingdom. Sickle cell status was based on the International Classification of Diseases, Tenth Revision (ICD-10) or mutations in the HBB gene. Diagnoses of diseases were obtained from ICD-10 and self-reports. Associations of sickle cell trait and diseases were tested using logistic regression, adjusting for age at recruitment, sex, and genetic background (top 10 principal components). RESULTS: Among the 8019 Blacks in the UKB, 699 (8.72%) were sickle cell trait carriers; the rate was significantly higher in females (9.74%) than males (7.48%), P = .0005. Sickle cell trait was under-diagnosed; most heterozygous hemoglobin subunit beta (HBB) gene Glu6Val carriers did not have a sickle cell trait ICD-10 record. Compared with non-sickle cell trait, sickle cell trait carriers had significantly increased risk for type 2 diabetes; odds ratio 1.38; 95% confidence interval, 1.12-1.68; P = .002. Sickle cell trait was also significantly associated with increased risk for renal diseases (rhabdomyolysis, end-stage renal disease, chronic kidney disease, renal papillary necrosis) and vascular diseases (hypertension, retinopathy, non-ischemic stroke), P < .05. While most of these diseases are complications/comorbidities of diabetes, their associations with sickle cell trait remained significant after adjusting for diabetes. Association with end-stage renal disease was stronger in subjects without diabetes, odds ratio 6.45; 95% confidence interval, 1.93-19.61; P = .001. CONCLUSIONS: Sickle cell trait is significantly associated with increased risk for diabetes and diabetes-related complications/comorbidities.

Association of Sickle Cell Trait with Risk and Mortality of COVID-19: Results from the United Kingdom Biobank.

Sickle cell trait (SCT) carriers inherit one copy of the Glu6Val mutation in the hemoglobin gene and is particularly common in Black individuals (5-10%). Considering the roles of hemoglobin in immune responses and the higher risk for coronavirus disease (COVID-19) among Black individuals, we tested whether Black SCT carriers were at increased risk for COVID-19 infection and mortality according to the United Kingdom Biobank. Among Black individuals who were tested for COVID-19, we found similar infection rates among SCT carriers (14/72; 19.7%) and noncarriers (167/791; 21.1%), but higher COVID-19 mortality rates among SCT carriers (4/14; 28.6%) than among noncarriers (21/167; 12.6%) (odds ratio [OR], 3.04; 95% confidence interval [CI], 0.69-11.82; P = 0.12). Notably, SCT carriers with preexisting diabetes had significantly higher COVID-19 mortality (4/4; 100%) than those without diabetes (0/10; 0%; (OR, 90.71; 95% CI, 5.66-infinite; P = 0.0005). These findings suggest that Black SCT carriers with preexisting diabetes are at disproportionally higher risk for COVID-19 mortality. Confirmation by larger studies is warranted.