Introduction to Biostatistics - Lecture 2: Statistical Inference Procedures

This presentation provides an overview of statistical inference procedures in biostatistics, including: hypothesis test for population average; hypothesis test for comparing means; and, power and sample size

Introduction to Biostatistics - Lecture 3: Statistical Inference for Proportions

This presentation provides an overview of statistical inference for proportions, to address how to estimate the probability of an event in a population of a certain size. Topics include confidence intervals, Chi-square tests, and Fisher\u27s Exact test

Introduction to Biostatistics - Lecture 1: Introduction and Descriptive Statistics

This presentation provides an overview of biostatistics and the basic principles and applications of statistics to problems in clinical and public health settings

Statistical Models to Assess Associations between the Built Environment and Health: Examining Food Environment Contributions to the Childhood Obesity Epidemic.

Models are developed and applied to examine the associations between built environment features and health. These developments are motivated by studies examining the contribution of features of the built food environment near schools, such as availability of fast food restaurants and convenience stores, to children’s body weight. The data used in this dissertation come from a surveillance database that captures body weight and other characteristics for all children in 5th, 7th, and 9th grades enrolled in public schools in California during 2001-2010 and a commercial data source that contains the locations of all food establishments in California for the same time period. First, we develop a hierarchical multiple informants model (HMIM) for clustered data that estimates the marginal association of multiple built environment features and formally tests if the strength of their association differs with the outcome. Using this new model, we establish that the contribution of the availability of convenience stores to children’s body mass index z-scores (BMIz) is stronger than that of fast food restaurants. Second, we propose to use a distributed lag model (DLM) to examine whether and how the association between the number of convenience stores and children’s BMIz decays with longer distance from schools. In this model, distributed lag (DL) covariates are the number of convenience stores within several contiguous “ring”-shaped areas from schools rather than circular buffers, and their coefficients are modeled as a function of distance, using smoothing splines. We find that associations are stronger with closer proximity to schools and vanish by about 2 miles from school locations. Third, we develop a hierarchical distributed lag model (HDLM) to systematically examine the variability of the built environment association across regions to help address a yet unanswered question in the built environment literature: whether and how activity spaces relevant to health vary across regions. We find DL coefficients vary across regions, implying that variation in activity spaces also exists. We also identify areas where children’s BMIz is more vulnerable to built environment factors. This dissertation provides novel methods with which to study how built environment factors affect health.PhDBiostatisticsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/110362/1/jongguri_1.pd

Hierarchical multiple informants models: examining food environment contributions to the childhood obesity epidemic

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102625/1/sim5967.pd

Stroke Quality Measures in Mexican Americans and Non-Hispanic Whites

Mexican Americans (MAs) have been shown to have worse outcomes after stroke than non-Hispanic Whites (NHWs), but it is unknown if ethnic differences in stroke quality of care may contribute to these worse outcomes. We investigated ethnic differences in the quality of inpatient stroke care between MAs and NHWs within the population-based prospective Brain Attack Surveillance in Corpus Christi (BASIC) Project (February 2009- June 2012). Quality measures for inpatient stroke care, based on the 2008 Joint Commission Primary Stroke Center definitions were assessed from the medical record by a trained abstractor. Two summary measure of overall quality were also created (binary measure of defect-free care and the proportion of measures achieved for which the patient was eligible). 757 individuals were included (480 MAs and 277 NHWs). MAs were younger, more likely to have hypertension and diabetes, and less likely to have atrial fibrillation than NHWs. MAs were less likely than NHWs to receive tPA (RR: 0.72, 95% confidence interval (CI) 0.52, 0.98), and MAs with atrial fibrillation were less likely to receive anticoagulant medications at discharge than NHWs (RR 0.73, 95% CI 0.58, 0.94). There were no ethnic differences in the other individual quality measures, or in the two summary measures assessing overall quality. In conclusion, there were no ethnic differences in the overall quality of stroke care between MAs and NHWs, though ethnic differences were seen in the proportion of patients who received tPA and anticoagulant at discharge for atrial fibrillation

Persistent ischemic stroke disparities despite declining incidence in Mexican Americans

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102622/1/ana23972.pd

Geographic Variation of Statin Use Among US Nursing Home Residents With Life-limiting Illness

BACKGROUND: Medically compromised nursing home residents continue to be prescribed statins, despite questionable benefits. OBJECTIVE: To describe regional variation in statin use among residents with life-limiting illness. RESEARCH DESIGN: Cross-sectional study using 2016 Minimum Data Set 3.0 assessments linked to Medicare administrative data and health service utilization area resource files. SETTING: Nursing homes (n=14,147) within hospital referral regions (n=306) across the United States. SUBJECTS: Long-stay residents (aged 65 y and older) with life-limiting illness (eg, serious illness, palliative care, or prognosis \u3c 6 mo to live) (n=361,170). MEASURES: Prevalent statin use was determined by Medicare Part D claims. Stratified by age (65-75, 76 y or older), multilevel logistic models provided odds ratios with 95% confidence intervals. RESULTS: Statin use was prevalent (age 65-75 y: 46.0%, 76 y or more: 31.6%). For both age groups, nearly all resident-level variables evaluated were associated with any and high-intensity statin use and 3 facility-level variables (ie, higher proportions of Black residents, skilled nursing care provided, and average number of medications per resident) were associated with increased odds of statin use. Although in residents aged 65-75 years, no associations were observed, residents aged 76 years or older located in hospital referral regions (HRRs) with the highest health care utilization had higher odds of statin use than those in nursing homes in HRRs with the lowest health care utilization. CONCLUSIONS: Our findings suggest extensive geographic variation in US statin prescribing across HRRs, especially for those aged 76 years or older. This variation may reflect clinical uncertainty given the largely absent guidelines for statin use in nursing home residents

Physical frailty and cognitive impairment in older nursing home residents: a latent class analysis

BACKGROUND: Little is known about the heterogeneous clinical profile of physical frailty and its association with cognitive impairment in older U.S. nursing home (NH) residents. METHODS: Minimum Data Set 3.0 at admission was used to identify older adults newly-admitted to nursing homes with life expectancy \u3e /=6 months and length of stay \u3e /=100 days (n = 871,801). Latent class analysis was used to identify physical frailty subgroups, using FRAIL-NH items as indicators. The association between the identified physical frailty subgroups and cognitive impairment (measured by Brief Interview for Mental Status/Cognitive Performance Scale: none/mild; moderate; severe), adjusting for demographic and clinical characteristics, was estimated by multinomial logistic regression and presented in adjusted odds ratios (aOR) and 95% confidence intervals (CIs). RESULTS: In older nursing home residents at admission, three physical frailty subgroups were identified: mild physical frailty (prevalence: 7.6%), moderate physical frailty (44.5%) and severe physical frailty (47.9%). Those in moderate physical frailty or severe physical frailty had high probabilities of needing assistance in transferring between locations and inability to walk in a room. Residents in severe physical frailty also had greater probability of bowel incontinence. Compared to those with none/mild cognitive impairment, older residents with moderate or severe impairment had slightly higher odds of belonging to moderate physical frailty [aOR (95%CI)moderate cognitive impairment: 1.01 (0.99-1.03); aOR (95%CI)severe cognitive impairment: 1.03 (1.01-1.05)] and much higher odds to the severe physical frailty subgroup [aOR (95%CI)moderate cognitive impairment: 2.41 (2.35-2.47); aOR (95%CI)severe cognitive impairment: 5.74 (5.58-5.90)]. CONCLUSIONS: Findings indicate the heterogeneous presentations of physical frailty in older nursing home residents and additional evidence on the interrelationship between physical frailty and cognitive impairment

Statin Discontinuation and Life-Limiting Illness in Non-Skilled Stay Nursing Homes at Admission

OBJECTIVES: To estimate 30-day statin discontinuation among newly admitted nursing home residents overall and within categories of life-limiting illness. DESIGN: Retrospective cohort using Minimum Data Set 3.0 nursing home admission assessments from 2015 to 2016 merged to Medicare administrative data files. SETTING: U.S. Medicare- and Medicaid-certified nursing home facilities (n = 13,092). PARTICIPANTS: Medicare fee-for-service beneficiaries, aged 65 years and older, newly admitted to nursing homes for non-skilled nursing facility stays on statin pharmacotherapy at the time of admission (n = 73,247). MEASUREMENTS: Residents were categorized using evidence-based criteria to identify progressive, terminal conditions or limited prognoses ( \u3c 6 months). Discontinuation was defined as the absence of a new Medicare Part D claim for statin pharmacotherapy in the 30 days following nursing home admission. RESULTS: Overall, 19.9% discontinued statins within 30 days of nursing home admission, with rates that varied by life-limiting illness classification (no life-limiting illness: 20.5%; serious illness: 18.6%; receipt of palliative care consult: 34.5%; clinician designated as end-of-life: 45.0%). Relative to those with no life-limiting illness, risk of 30-day statin discontinuation increased with life-limiting illness severity (serious illness: adjusted risk ratio (aRR) = 1.06; 95% confidence interval (CI) = 1.02-1.10; palliative care index diagnosis: aRR = 1.15; 95% CI = 1.10-1.21; palliative care consultation: aRR = 1.58; 95% CI = 1.43-1.74; clinician designated as end of life: aRR = 1.59; 95% CI = 1.42-1.79). Nevertheless, most remained on statins after entering the nursing home regardless of life-limiting illness status. CONCLUSION: Statin use continues in a large proportion of Medicare beneficiaries after admission to a nursing home. Additional deprescribing research, which identifies how to engage nursing home residents and healthcare providers in a process to safely and effectively discontinue medications with questionable benefits, is warranted