Browsing by Subject "mortality"

Now showing 1 - 9 of 9
  • Thumbnail Image
    Item
    Birthing Minnesota: The Associations of Structural Racism and Neighborhood Characteristics with the Health of Minnesota’s Birthing Population, Pregnancy through Postpartum
    (2021-12) Mentzer, Kari
    Structural racism in Minnesota communities may be associated with adverse birth outcomes such as preterm birth, low birthweight, severe maternal morbidity, and death for birthing people. This dissertation provides a comprehensive report on the birthing outcomes of Minnesota people who gave birth 2011-2019 including the rates of prenatal risks (e.g. inadequate prenatal care, diabetes, and hypertension), adverse pregnancy outcomes (e.g. premature birth, low birthweight, fetal death), maternal morbidity (e.g. transfusion, unplanned hysterectomy, admission to ICU), and death (e.g. pregnancy-related, pregnancy-associated, all-cause after the first year). The relationship between structural racism in Minnesota and the health outcomes experienced by birthing people, specifically Black and American Indian people, during the perinatal period and in the years following childbirth is examined using the Index of Concentration at the Extremes (ICE) in a treatment effects model. In areas with the highest exposure to structural racism (according to ICE measures), neighborhood characteristics (e.g. access to healthy food, presence of green spaces, available quality education) may be associated with better than expected outcomes when the quality and number of resources are high. A logistic model was used to detail the association of increasing neighborhood resources to birth outcomes for individuals exposed to high levels of structural racism.
  • Thumbnail Image
    Item
    Bringing About Pro-Environment Behavior Through Policies and Social Norms
    (2019-07) SANKAR, ASHWINI
    As human population and consumption have risen, waste generation and air pollution have also increased leading to steady environmental degradation. To stem overflowing landfills and combat air pollution, policies and social norms have often been used as tools to bring about change. My dissertation analyzes the impact of these tools to achieve pro-environment behavior. The first chapter tries to understand two such behaviors, i.e., how to increase recycling and reduce waste. They are key to protecting natural resources, but households probably do not derive any benefit from recycling other than social approval. Based on a theoretical model I built for households, I show that when the social norm of recycling increases, the recycling rate of the household rises and waste per capita falls. My paper is one of the first to test these propositions empirically for Minnesota data using an instrumental variable setup. I show that while waste per capita declines significantly with an increase in social capital, recycling rate does not seem to be influenced by social capital. My second chapter studies the impact of environmental regulations in India on mortality that includes all causes and all ages (or mortality). We know that chronic exposure to air pollution is more harmful to adults than babies and hence focus on mortality as the outcome, for the first time for India. Using a difference-in-differences framework, in the first part of the paper, I show that environmental regulations in India have led to a significant drop in mortality. The second part analyzes the effect of different pollution types on mortality, where I show that PM2:5 exposure is more harmful to mortality (but not infant mortality) than TSP. This further strengthens the claim that policies should focus on adults and shift its focus from TSP to PM2:5 to get greater gains in health. The last chapter studies the functional form of the relationship between PM2:5 concentrations and mortality for the first time for India. The shape of this concentration-response curve will determine if the air in India affects public health at a different or the same rate as the U.S. baseline rate. My paper is one of the first studies to analyze this relationship using panel data for India, without simply extrapolating coefficients from U.S. or European data, following a rigorous identification strategy. I then arrive at the relative risk of mortality estimates at higher pollution concentrations as well as the estimated lives saved due to the reduction in pollution exposure.
  • Thumbnail Image
    Item
    Development of individual tree based stand growth simulators : progress and applications.
    (University of Minnesota, 1980-08) Ek, Alan R.; Dudek, Albert
    Research since the early 1960's on the development of individual tree based stand growth simulators is reviewed with respect to evolving methodologies for treating overstory growth, competition, mortality, reproduction, stochastic errors, calibration, and validation. The present and potential accuracy and precision of the models is discussed along with applications to date. Strategies for using the models for succession analysis and decision-making regarding choices among management treatments are also considered. It is apparent that these models can be expensive to develop, but represent one of the most powerful approaches available for predicting forest change. They are also a convenient basis for forest managers and ecological scientists to work together effectively. Pitfalls in the process of model development and usage are also discussed.
  • Thumbnail Image
    Item
    Evaluating American marten habitat quality using airborne light detection and ranging (LiDAR) data
    (2018-09) Joyce, Michael
    Understanding the factors that influence animal distribution and density is a central theme in animal ecology. For imperiled species, understanding the resources and conditions that allow animals to occupy the landscape is critical for development of effective conservation strategies. Not surprisingly, habitat selection is a common focus of wildlife research. This dissertation project focused on addressing two main challenges that limit the application of a fitness-based approach to understanding habitat selection: 1) data on fine-scale habitat resources and conditions required for the development and testing of resource- and fitness-based definitions of habitat are generally not available across entire study areas, and 2) indirect measurements of fitness (e.g., survival or reproductive success) are often not considered when assessing habitat selection patterns, in part, because of the difficulty of measuring fitness correlates for free-ranging animals with long life-spans and large home ranges. My first two chapters address the first challenge by using airborne light detection and ranging (LiDAR) data to measure fine-scale characteristics known to be selected by my focal species, American martens (Martes americana). In Chapter 1, I demonstrate that LiDAR data can be used to detect individual pieces of coarse woody debris, an important habitat component that provides martens with foraging habitat and access to the subnivean layer. In Chapter 2, I created statistical models to estimate 5 response variables relating to tree size and density and evaluated how well models will perform when imputed across the entire study area. I found that the models I created performed well when applied to new data, but that performance depended on the response variable being modeled. My last two chapters address the second challenge by evaluating how landscape and forest structure influence mortality risk for martens. In Chapter 3, I evaluated factors influencing harvest mortality risk. I found that martens living close to roads have higher harvest risk because trappers use roads to set and check traps efficiently. Consequently, distribution of roads can have a profound impact on habitat quality, which has important implications for gene flow and population structure. In Chapter 4, I used LiDAR data and classified satellite imagery to examine the role of forest structure in mediating interactions between martens and predators. I found that sites where martens were killed by predators were associated with non-forested areas including wetlands, shrublands, and young and regenerating forests. Although martens generally avoid non-forested areas that are associated with higher predation risk, martens must move near or through risky areas while moving across heterogeneous, managed landscapes.
  • Thumbnail Image
    Item
    Fishing Cat Ecology: Food Habits, Home Ranges, Habitat Use and Mortality in a Human-Dominated Landscape around Khao Sam Roi Yot, Peninsular Thailand
    (2015-06) Cutter, Passanan
    Abstract Despite their global status as an endangered species, many aspects of fishing cat (Prionailurus viverrinus) ecology have not been studied in detail in the wild. The objectives of this study were to understand food habits, habitat use, home range patterns, and causes of mortality in a predominantly agricultural landscape in the area in and around Khao Sam Roi Yot National Park, Prachuap Khiri Khan Province, peninsular Thailand. Few studies have been conducted on the food habits of wild fishing cats and none has been conducted in Southeast Asia. I identified prey remains in fishing cat scats to estimate composition and relative occurrence of major prey groups in the feces of 194 fishing cat scats collected over an approximately 35 km2 area. The proportion of prey remains found in scats was 42% fish, 24% mammals, 24%, birds, 5% reptiles, and 2% crustaceans. There was a significant difference in seasonal prey composition (p = 0.001). During the dry season, 47% of prey remains found was fish, 11 % mammal, 29% bird, 11% reptile, and 3% crustacean. In the wet season, proportions were 36% fish, 39% mammal, 20% bird, 2% reptile, and 1% crustacean. In this study, fishing cat diet varied more than previously reported, both in terms of the diversity of prey and in the proportions of major groups recorded between seasons. To study the home range, habitat use, and mortality of fishing cats, I captured seventeen cats (seven females and 10 males) using box traps and fitted 16 with VHF radio collars. Data from these animals (>1000 locations) were used to estimate home range size and habitat selection. Home range size was estimated using 100% Minimum Convex Polygon (MCP) and the 95% Fixed Kernel (FK) methods. Fishing cats essentially maintained their core area for the duration of the study despite seasonal changes in diet. For the 100% MCP, the area of the male annual home range, F5 was 13.5 km2 and M8 was 4 km2 and the mean for female annual home ranges (n=4) was 4.0 km2. Whereas, the 95% estimates for the male annual home range was 8.8 km2, and the mean annual home range for females was 3.9 km2. Seasonal home range was estimated for one male. His wet season 100% MCP was 10.8 km2, and his 95% fixed kernel was 12.6 km2. In the dry season his 100% MCP home range was 5.7 km2 and the 95% fixed kernel home range was 8.9 km2. For females (n=4), mean wet season 100% MCP home range was 3.2 km2 and the mean 95% fixed kernel was 3.1 km2. The dry season mean 100% MCP was 3.0 km2 and the mean 95% fixed kernel was 3.2 km2. There is evidence of overall home range overlap between females but their 50% area had no overlap. Fishing cats used aquaculture areas and rice fields more frequently, than mangrove restoration areas, and coconut plantations, and human settlement and limestone hills were avoided. One animal used primarily mangrove vegetation (97% of all locations). Coconut plantation was a relatively rare vegetation type within the study area, but it was the most used habitat for one animal in the dry season. Of 16 cats originally collared, five died from confirmed poaching or retribution killing (31.3%), dead from unknown causes (n=6, 37.5%), unknown fate (n=3, 18.8%), and collar malfunction (n=2, 12.5%). Considering that fishing cats have been known to live to 10 years of age, the sample in this study sustained a relatively high mortality rate. Because poaching and retaliatory killing was the main cause of death, the most effective conservation effort for this species in coastal Thailand should focus on decreasing human-fishing cat conflict and poaching.  
  • Thumbnail Image
    Item
    Mortality and Cause of Death Following Pediatric Cardiac Surgery for Congenital Heart Defects
    (2021-06) Zmora, Rachel
    Congenital heart defects (CHD) affect almost 1% of births. The primary method for managing these defects is surgery. These analyses used data from the Pediatric Cardiac Care Consortium (PCCC), a large, US-based registry of pediatric interventions for CHDs. The PCCC was previously linked to the National Death Index and was linked to the American Medical Association Physician Masterfile as part of this dissertation. The first two analyses examined the associations between surgeon and center characteristics and post-surgical mortality using multilevel modeling. These analyses examined procedure-specific volume at the surgeon and center levels as well as training center status at the center level and years since graduation from medical school at the surgeon level. In the third analysis, multiple cause of death data were examined to determine the burden of contributing causes of death. Standardized mortality ratios and competing risk Cox regression compared these results with those calculated using underlying cause of death. The first analysis found that after adjusting for known patient-level risk factors, center factors including procedure-specific volume were not associated with early post-discharge mortality. The second analysis of short and medium term mortality demonstrated a consistent center-level association between procedure-specific volume and mortality among several complex repairs. No association was observed among patients with relatively simple ventricular septal defect repairs. Finally, we found that standardized mortality ratios based on underlying cause of death underestimated the burden of death associated with injury as well as perinatal, infectious, endocrine, genitourinary, and circulatory diseases. These differences varied by age and defect severity. Perinatal and endocrine disease were highest among those with severe defects. Differences in mortality due to infection showed a bimodal association with age at the time of death. The combination of multi-level modeling and multiple cause of death methods leveraged in these analyses advances the understanding of the roles of healthcare systems and multiple causes of death.
  • Thumbnail Image
    Item
    A national survey of managed honey bee 2013–2014 annual colony losses in the USA
    (2015) Lee, Kathleen V.; Steinhauer, Nathalie; Rennich, Karen; Wilson, Michael E.; Tarpy, David R.; Caron, Dewey M.; Rose, Robyn; Delaplane, Keith S.; Baylis, Kathy; Lengerich, Eugene J.; Pettis, Jeff; Skinner, John A.; Wilkes, James T.; Sagili, Ramesh; vanEngelsdorp, Dennis
    Honey bee colony losses are a major concern in the USA and across the globe. Long-term data on losses are critical for putting yearly losses in context. US colony loss surveys have been conducted yearly since the winter of 2006–2007. Here, we report the results from the eighth annual survey on winter losses and the second annual survey of summer and annual losses. There were 7425 valid respondents (7123 backyard, 190 sideline, and 112 commercial beekeepers) managing 497,855 colonies, 19 % of the total US colonies. Total losses reported were 19.8 % [95 % CI 19.3–20.3 %] over the summer, 23.7 % [95 % CI 23.3–24.1 %] over the winter, and 34.1 % [95 % CI 33.6–34.6 %] for the whole year. Average losses were 15.1 % [95 % CI 14.5–15.7 %] over the summer, 44.8 % [95 % CI 43.9–45.7 %] over the winter, and 51.1 % [95 % CI 50.2–51.6 %] for the whole year. While total winter loss was one of the lowest reported in 8 years, 66 % of all beekeepers had higher losses than they deemed acceptable.
  • Thumbnail Image
    Item
    Occupational Radiation, Neighborhoods and Circulatory Disease Incidence and Mortality
    (2019-08) Bustamante Callejas, Gabriela
    Background: Exposure to ionizing radiation has been primarily linked with the development of cancer, but in recent decades it has also been recognized to be a risk factor for circulatory diseases (CDs). High doses of ionizing radiation above 500mGy are associated with damage of the circulatory system and increased mortality from circulatory diseases (CD). The biological mechanism is hypothesized to include inflammation, oxidative stress, changes in platelet activity, DNA damage, endothelial dysfunction and cell death. However, the risks of occupational exposure to low protracted doses of medical ionizing radiation on CD mortality are not well understood. The risk of CD is also influenced by an individual’s social environment, and this may modify the effect of occupational exposures like ionizing radiation. Most studies on the association between neighborhood context and coronary heart disease found increased risk of this disease among residents of neighborhoods of lower socioeconomic status. The socio-biological mechanism of this relationship is multifactorial, and it includes the physical environment, availability of services, neighborhood social interactions, experiential perceptions, spread of disease, stress levels, health behaviors and other shared factors. To understand the effect of cumulative ionizing radiation and the neighborhood context on CD, we used longitudinal data from the US Radiologic Technologists (USRT) study and the US Census Bureau. The USRT is a large national historical cohort of 146,022 radiation technologists that has followed participants since 1982 through four comprehensive study waves. It is known that the average participation rate across these four questionnaires was 68%, but the characteristics of participants and non-participants have not been compared to date. If non-participation and attrition are not a random process, this could introduce bias to any effect estimates calculated with this data, including estimates of CD incidence and mortality. Objective: The overall aim of the current thesis was to investigate the effect of protracted exposure to low doses of occupational radiation on CD incidence and mortality and assess if these associations are influenced by the residential neighborhood socioeconomic status (nSES) or by sequential participation bias. Manuscript 1: Aim: Examine the dose-response relationship between low chronic doses of occupational radiation exposure and CD mortality in a large cohort of radiologic technologists. Methods: 109,300 radiologic technologists in the US were followed for mortality from completion of baseline surveys during 1983-89 or 1994-98 through 2012. Using discrete time hazard models, HR and 95%CI were estimated for the association between cumulative ionizing radiation (as badge and organ doses) and mortality from any CD, ischemic heart disease (IHD) and cerebrovascular disease (CeVD). Calendar year was included as a time scale and adjusted for age as a time-varying covariate, sex, race, ethnicity, BMI and smoking. Results: We found evidence of increased risk of CD mortality with increased cumulative exposure to occupational radiation. For every 100mSv increase in cumulative badge dose, the risk of mortality from any CD increased in 3% (95% CI 2-4%) adjusted for age, sex, race, ethnicity, BMI and smoking. For every 100mGy increase in heart dose, the HR for IHD mortality was 1.07 (95% CI 1.02 – 1.13) and the hazard ratio per 100mGy increase in brain dose was 1.39 (95%CI 1.14 – 1.64) for CeVD. Categorical analyses supported this linear trend for all outcomes. There was evidence of effect modification by gender for CD and IHD mortality (p-value for interaction < 0.001 for both), but not by BMI or certification year. Manuscript 2: Aim: Determine whether the association between cumulative occupational radiation exposure on CD incidence and mortality is confounded or modified by residential nSES. Methods: Tertiles of nSES were created from an nSES index calculated for each block-group in the U.S. using 6 components from the 1990 Census and assigned it to participants by geocoding their 1990 mailing address. The confounding role of nSES tertiles was assessed by including it in discrete time hazard models along radiation exposure and adjusting for educational attainment. To determine the presence of effect modification by nSES tertiles, we tested a two-way multiplicative interaction between nSES tertiles and radiation, and assessed an additive interaction using the relative excess risk due to interaction (RERI). Results: Compared to residents from the top tertile of nSES, technologists from low-nSES areas had an elevated risk of overall CD mortality, IHD mortality and incidence, and CeVD incidence with (HRs ranging from 1.21 to 1.31), but not for CeVD mortality (HR: 0.97, 95%CI: 0.80-1.18). We found no evidence of confounding by nSES on the association between radiation and any CD outcomes. There was evidence of a multiplicative interaction between nSES tertiles and radiation exposure for all mortality outcomes (p-value for interaction: <0.001 for overall CD, 0.003 for IHD and 0.004 for CeVD), but not for incidence. People from high nSES had higher HRs for mortality than low-nSES residents for the same radiation dose. Manuscript 3: Aim: Compare the characteristics of participants and non-participants of each survey and estimate the impact of low chronic exposure to radiation on incidence and mortality from ischemic heart disease (IHD) and cerebrovascular disease (CeVD) adjusting for possible selection bias. Methods: Our main exposure was cumulative radiation exposure estimated for 110,374 technologists. After identifying predictors of participation from baseline and survey information, we created inverse probability weights (IPW) of participation to account for selection bias and included them in discrete time hazard models of the association of radiation and circulatory outcomes. Results: Being younger, female, white, married, non-smoker, having a normal BMI, reporting good health status, and living in a rural area was associated higher probability of participating in any survey. The difference between our estimates with or without IPWs ranged between 1-4%-points for IHD incidence, IHD mortality and CeVD mortality and supported evidence of increased risk of disease with higher chronic radiation exposure. For CeVD incidence, the weighted estimate was 15%-points lower than the unweighted estimate, but it still suggested an increased risk of CeVD incidence from chronic exposure to ionizing radiation. Conclusion: This study of medical radiation technologists who were chronically exposed to low-doses of radiation found consistent evidence of radiation-induced circulatory effects below the current 0.5Gy threshold. In addition, we found that nSES was independently associated with CD mortality and incidence in a group of US technologists occupationally exposed to low-doses of radiation, but there was no consistent evidence that it confounded the association between radiation and CD outcomes. We found a multiplicative two-way interaction between radiation and nSES, where residents of high nSES areas had higher risk of CD mortality than residents of low nSES exposed to the same radiation dose. In terms of our selection bias analysis, we found only a small impact of selection bias on our estimates of the association of cumulative radiation exposure and CD outcomes despite consistent differences in the characteristics of participants and non-participants.
  • Thumbnail Image
    Item
    Occurrence and Survival of Zebra Mussel (Dreissena polymorpha) Veliger Larvae in Residual Water Transported by Recreational Watercraft
    (2018-12) Doll, Adam
    Zebra mussels (Dreissena polymorpha) are an aquatic invasive species (AIS) that have spread to many waterbodies in North America and transient recreational watercraft are one of the primary pathways of spread. Best management practices for reducing the risk of spreading AIS include draining all water from watercraft before leaving a water body, but removing all water is impractical. Uncertainly exists about whether zebra mussel larvae (veligers) could reside within the “residual water” that remains after draining and survive overland transport to a new water body. At two Minnesota, USA water bodies (Gull Lake and Lake Minnetonka) from July – August (2016-2017) we collected over 300 samples of residual water from recreational watercraft; compartments included ballast tanks, live wells, sterndrive engines, and others. Roughly half (48%) of these samples contained no veligers and the majority (75%) contained five or fewer. Sterndrive engines and ballast tanks ranked 1st and 2nd for volumes of residual water (median of 4945 and 2650 milliliters, respectively), Ballast tank samples contained the largest median number of veligers per sample (247) and sterndrive engines the highest maximum number of veligers (about 4500 for 2 out of 38 engines sampled). We conducted laboratory experiments on veliger survival in residual water of live wells due to the high frequency of fishing boats moving between water bodies, and ballast tanks given their high likelihood of containing veligers. We exposed live well samples to 20°, 27°, 32°, and 38°C air temperature and ballast tanks to 20° and 32°C. For veligers in live well residual water, we observed greater than or equal to 95% mortality after 5 hours of exposure at all temperatures. These same levels of mortality were reached more slowly in ballast tanks (greater than or equal to 95% mortality at both temperatures achieved at 48 hours). Additional prevention steps should be taken (e.g. using hot water) to reduce the risk of transporting living veligers in residual water.