Browsing by Subject "Mortality"
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Item Corn earworm (Helicoverpa zea Boddie), cold hardiness, and climate change: implications for future distributions and IPM.(2010-09) Morey, Amy ClaireThe cold hardiness of Helicoverpa zea (Boddie) pupae was assessed using three laboratory methods: supercooling point (SCP), lower lethal temperature (LLTemp), and lower lethal time (LLTime) determination. Mean SCPs for pupae ranged between -16.4°C and -19.5°C, depending on whether pupae were in diapause or had been acclimated. The LLTemp at which 50% mortality occurred (LT50) for diapausing and non-diapausing pupae was -8.8°C and -12.4°C, respectively, though the LLTemp mortality curves were not significantly different. The time until 95% mortality for non-diapausing pupae held at -10°C, -5°C, 0°C, and 5°C was 7.2, 81.6, 502.3, and 1073.4 hrs, respectively. Time until 95% mortality for diapausing pupae held at 0°C and 5°C was 2660.19 and 2796.92 hrs, respectively. Sex did not have an influence on cold hardiness. Diapause greatly enhanced cold hardiness in pupae as indicated by a significantly lower mean SCP and longer time to reach mortality at a given temperature compared to non-diapausing pupae. However, given mean SCP comparisons, acclimation of non-diapausing pupae had a cold hardening effect comparable to diapause. In-field evaluation of overwintering H. zea survival in southern Minnesota showed that temperature was a severely limiting factor in overwintering success, though likely not responsible for complete mortality. Laboratory data, coupled with the field results suggest that a small proportion of pupae may be able to survive in Minnesota. However, field observations also suggest that sufficient degree days may not be available during autumn in southern Minnesota to allow for substantial pupation before the onset of winter, thus eliminating the potential for an overwintering population. Using the cold hardiness data generated for diapausing pupae, the present and future distributions of H. zea in North America were calculated with the modeling software CLIMEX. The resulting maps depicting the current distribution of H. zea from CLIMEX did not agree with what is currently understood for H. zea overwintering distributions and overall geographic suitability; contrary to convention, cold stress is shown to not be a significant constraint to H. zea suitability for most of the U.S. Despite the discrepancies in current projections, the present study corroborated Diffenbaugh et al. (2008) in illustrating a northern expansion of suitability for H. zea, under future climate change. The implications of potential northern expansion in the geographic range of H. zea are discussed within the context of future Integrated Pest Management (IPM) needs for sweet corn, as well as other vegetable and field crops throughout North America.Item Extreme weather and mortality among a nationwide cohort of Veterans with COPD(2023) Rau, AustinClimate change is increasing the frequency, severity and duration of extreme weather events. Individuals with climate sensitive diseases such as chronic respiratory diseases are at an enhanced risk of health challenges due to climate change. However, there is a lack of individual level studies examining how extreme weather events such as heat and cold waves may increase the risk of mortality among individuals with chronic obstructive pulmonary disease (COPD), a climate sensitive respiratory disease. Using nationwide individual level health data from the Veterans Health Administration, three studies were designed to estimate heat and cold wave associated mortality risk among this susceptible population.The first study evaluated heat and cold wave mortality risk among the entire population of patients with COPD and examined health disparities by individual characteristics including gender, age, race and ethnicity. Results indicated cisgender females had an increased heatwave associated mortality risk. While some racial disparities in mortality risk were detected, the evidence was weak. The second study further examined disparities in heat and cold wave associated mortality via less commonly studied effect measure modifiers including comorbidities, smoking status and urbanicity. Patients with concurrent COPD and asthma had a greater risk of heatwave related mortality whereas patients with COPD alone had the greatest cold wave associated mortality risk. Smokers and patients living in urban settings had enhanced risk of both heat and cold wave related mortality. The third study assessed the added mortality risk incurred during compound climate hazards (droughts and heatwaves) among this susceptible population. Results indicated heatwaves that occurred during droughts had larger mortality risks compared to heatwaves during non-drought conditions. These three studies provide evidence that individuals with COPD are at risk of adverse health events from heat and cold waves and identified heterogeneities in risk based on characteristics including social, biological and geographical constructs. There is an apparent need in climate and health epidemiology for more large-scale individual level assessments of people with climate sensitive diseases. As contemporary impacts of climate change are realized, it is imperative to devote resources and energy into elucidating health risks associated with extreme weather events to identify and protect at-risk segments of the population.Item Investigating Infection-Related Hospitalization as a Risk Factor for Incident Heart Failure and Mortality among Heart Failure Patients(2023-06) Molinsky, RebeccaHF is a growing epidemic with an estimated prevalence of 6.5 million individuals in the U.S., and poor outcomes persist despite recent therapeutic advancements. Studies have shown that an inflammatory response to infections may become dysregulated, thereby promoting collateral myocardial damage that may result in HF. Infection is also a common cause of hospitalization among HF patients and may lead to poor prognosis and high mortality. Limited data exist examining the relationship between infection-related hospitalization (IRH) and HF along with HF subtypes, HF with preserved ejection fraction (HFpEF) and HF with reduced ejection fraction (HFrEF). Further, few studies have explored mortality rates following an IRH in HF patients or whether certain types of IRH are stronger predictors of mortality. This dissertation leveraged the strengths of large claims data (MarketScan) and a community-based study (ARIC) to address these limitations and parse out the dynamic relationship between infection-related hospitalization and HF with several manuscripts. The first manuscript, a case-crossover study of beneficiaries in the MarketScan databases, assessed the association between IRH and incident HF. IRH was associated with incident HF after both 1- and 3-months. The second manuscript investigated the association between IRH and long-term incident HF in the Atherosclerosis Risk in Communities study (ARIC). IRH was associated with a two-fold greater risk of incident HF, HFrEF, and HFpEF. Findings were stronger among those with HFpEF, for which treatment options are limited. Results from the first manuscript aligned with those of the second manuscript and both found respiratory, pneumonia, and blood/circulatory infections to have the strongest associations with incident HF. The third manuscript explored the relationship between IRH and mortality among HF patients in ARIC. IRH was associated with a two-fold greater risk of mortality among those with HFpEF, HFrEF, or unclassified HF. Respiratory, pneumonia, and other infections had the strongest associations with mortality. Our findings support prior literature linking IRH to HF risk and increased mortality among HF patients. These findings may have significant population-level implications given the high prevalence of IRH and the burden of HF on our aging society. Aim 1: Investigate the association between infection-related hospitalization and incident HF using U.S.-based claims data from MarketScan. Aim 2: Investigate the association between infection-related hospitalization and incident HF and HF subtypes (HFrEF or HFpEF) using a longitudinal community-based cohort study, ARIC. Aim 3: Among HF (HFrEF and HFpEF) patients, investigate the association between infection-related hospitalization and mortality using a longitudinal community-based cohort study, ARIC.Item An optimized classification system of acute kidney injury for predicting the short-term mortality after open heart surgery; comparison of current classification systems.(2010-05) Afshinnia, FarsadEpidemiologic studies need a unique operational definition of acute kidney injury (AKI) to compare outcomes. We aimed to compare prognostic value of change in serum creatinine with classification systems of AKI to predict 30day mortality after heart surgery. From VA database, 27410 eligible patients with stable baseline kidney function who had heart surgery from 1999 to 2005 were selected. There was a graded increase in mortality from stage A to stage C of all systems. Adjusted 30day mortality odds ratio starts to increase significantly after an acute rise ≥ 0.3 mg/dL of creatinine in CKD stages 1 and 2, and after 0.6 mg/dL increase in CKD stage 3. Area under ROC curve of change of creatinine from baseline was significantly higher than those of classification systems (P<0.001). In conclusion, compared to continuous increase of creatinine, classification systems of AKI misestimate mortality risk by collapsing predictive, clinically important data into categories.