Air pollution and COVID-19 mortality in the United States: Strengths and limitations of an ecological regression analysis.

Assessing whether long-term exposure to air pollution increases the severity of COVID-19 health outcomes, including death, is an important public health objective. Limitations in COVID-19 data availability and quality remain obstacles to conducting conclusive studies on this topic. At present, publicly available COVID-19 outcome data for representative populations are available only as area-level counts. Therefore, studies of long-term exposure to air pollution and COVID-19 outcomes using these data must use an ecological regression analysis, which precludes controlling for individual-level COVID-19 risk factors. We describe these challenges in the context of one of the first preliminary investigations of this question in the United States, where we found that higher historical PM2.5 exposures are positively associated with higher county-level COVID-19 mortality rates after accounting for many area-level confounders. Motivated by this study, we lay the groundwork for future research on this important topic, describe the challenges, and outline promising directions and opportunities.

Lipoprotein particle concentration measured by nuclear magnetic resonance spectroscopy is associated with gestational age at delivery: a prospective cohort study.

OBJECTIVE: To estimate the association between lipoprotein particle concentrations in pregnancy and gestational age at delivery. DESIGN: Prospective cohort study. SETTING: The study was conducted in the USA at the University of North Carolina. POPULATION: We assessed 715 women enrolled in the Pregnancy, Infection, and Nutrition study from 2001 to 2005. METHODS: Fasting blood was collected at two time points (<20 and 24-29 weeks of gestation). Nuclear magnetic resonance (NMR) quantified lipoprotein particle concentrations [low-density lipoprotein (LDL), high-density lipoprotein (HDL), very-low density lipoprotein (VLDL)] and 10 subclasses of lipoproteins. Concentrations were assessed as continuous measures, with the exception of medium HDL which was classified as any or no detectable level, given its distribution. Cox proportional hazards models estimated hazard ratios (HR) for gestational age at delivery adjusting for covariates. MAIN OUTCOME MEASURES: Gestational age at delivery, preterm birth (<37 weeks of gestation), and spontaneous preterm birth. RESULTS: At <20 weeks of gestation, three lipoproteins were associated with later gestational ages at delivery [large LDLNMR (HR 0.78, 95% CI 0.64-0.96), total VLDLNMR (HR 0.77, 95% CI 0.61-0.98), and small VLDLNMR (HR 0.78, 95% CI 0.62-0.98], whereas large VLDLNMR (HR 1.19, 95% CI 1.01-1.41) was associated with a greater hazard of earlier delivery. At 24-28 weeks of gestation, average VLDLNMR (HR 1.25, 95% CI 1.03-1.51) and a detectable level of medium HDLNMR (HR 1.90, 95% CI 1.19-3.02) were associated with earlier gestational ages at delivery. CONCLUSION: In this sample of pregnant women, particle concentrations of VLDLNMR , LDLNMR , IDLNMR , and HDLNMR were each independently associated with gestational age at delivery for all deliveries or spontaneous deliveries <37 weeks of gestation. These findings may help formulate hypotheses for future studies of the complex relationship between maternal lipoproteins and preterm birth. TWEETABLE ABSTRACT: Nuclear magnetic resonance spectroscopy may identify lipoprotein particles associated with preterm delivery.