Misclassification of the mediator matters when estimating indirect effects

Extremely poor Canadian women were recently observed to be largely advantaged on most aspects of breast cancer care as compared with similarly poor, but much less adequately insured, women in the United States. This historical study systematically replicated the protective effects of single-versus multipayer health care by comparing colon cancer care among cohorts of extremely poor women in California and Ontario between 1996 and 2011. The Canadian women were again observed to have been largely advantaged. They were more likely to have received indicated surgery and chemotherapy, and their wait times for care were significantly shorter. Consequently, the Canadian women were much more likely to experience longer survival times. Regression analyses indicated that health insurance nearly completely explained the Canadian advantages. Implications for contemporary and future reforms of U.S. health care are discussed.

Aims/hypothesisTo determine the extent to which gestational fasting and postload levels of glucose explain differences in infant fat mass between UK-born Pakistani and white British infants.MethodsAnalyses were undertaken in a prospective pregnancy cohort study of 1,415 women and their singleton live-born infants (629 white British and 786 Pakistani). Infant fat mass was assessed by cord-blood leptin levels and fetal insulin secretion by cord-blood insulin levels. Maternal OGTTs were completed at 26–28 weeks of gestation.ResultsPakistani women had higher fasting and postload glucose levels and greater incidence of gestational diabetes than white British women. Higher fasting and postload glucose levels were associated with higher cord-blood levels of insulin and leptin in all participants, irrespective of ethnicity. Cord-blood leptin levels were 16% (95% CI 6, 26) higher in Pakistani than in white British infants. After adjustment for fasting glucose levels, this difference attenuated to 7% (−3, 16), and with additional adjustment for cord-blood insulin levels it attenuated further to 5% (−4, 14). Path analyses supported the hypothesis that fasting glucose levels mediate the relationship of Pakistani ethnicity to greater fat mass at birth, as measured by cord-blood leptin levels; on average, 19% of this mediation involved fetal insulin secretion. Postload glucose levels did not act as an important mediator of ethnic differences in cord-blood leptin levels. Results were very similar when 130 women with gestational diabetes were removed.Conclusions/interpretationThese novel findings suggest a role of maternal pregnancy glycaemia in mediating differences in fat mass between Pakistani and white British infants.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-014-3386-6) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

IntroductionResearch has demonstrated that intensivist-led care of the critically ill is associated with reduced intensive care unit (ICU) and hospital mortality. The objective of this study was to evaluate whether a relation exists between intensivist cover pattern (for example, number of days of continuous cover) and patient outcomes among adult general ICUs in England.MethodsWe conducted a retrospective cohort study by using data from a pooled case mix and outcome database of adult general critical care units participating in the Intensive Care National Audit & Research Centre (ICNARC) Case Mix Programme. Consecutive admissions to participating units for the years 2010 to 2011 were linked to a survey of intensivist cover practices. Our primary outcome of interest was mortality at ultimate discharge from acute-care hospital.ResultsThe analysis included 80,122 patients admitted to 130 ICUs in 128 hospitals. Multivariable logistic regression analysis was used to assess the relation between intensivist cover patterns (days of continuous cover, grade of physician staffing at nighttime, and frequency of daily handovers) and acute hospital mortality, adjusting for patient case mix. No relation was seen between days of continuous cover by a single intensivist or grade of physician staffing at nighttime and acute hospital mortality. Acute hospital mortality and ICU length of stay were not associated with intensivist characteristics, intensivist full-time equivalents per bed, or years of clinical experience. Intensivist participation in handover was associated with increased mortality (odds ratio, 1.27; 95% confidence interval, 1.04 to 1.55); however, only nine units reported no intensivist participation.ConclusionsWe found no relation between days of continuous cover by a single intensivist or grade of physician staffing at nighttime and patient outcomes in adult, general ICUs in England. Intensivist participation in handover was associated with increased mortality; further research to confirm or refute this finding is required.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-014-0491-3) contains supplementary material, which is available to authorized users.