Academic Appointments

  • Instructor, Medicine

Professional Education

  • PhD, Johns Hopkins School of Public Health, Biostatistics (2011)
  • BA, St. Olaf College, Mathematics with minors in Statistics and Linguistics (2006)

Research & Scholarship

Current Research and Scholarly Interests

I am a senior biostatistician in the Quantitative Sciences Unit in the Department of Medicine. I am interested in developing and applying statistical methods to all areas of medicine and public health. I have worked closely with neuroscientists to improve statistical methods applied to neuroscience data and have contributed to public health research related to cancer screening, blood pressure control, disaster preparedness, and environmental health. My statistical research interests center around neurostatistics, time series analysis, and methods for longitudinal or clustered data. Last but not least, I enjoy mentoring clinicians, researchers, and students who are interested in learning statistics.


Journal Articles

  • Modern Statistical Modeling Approaches for Analyzing Repeated-Measures Data NURSING RESEARCH Hayat, M. J., Hedlin, H. 2012; 61 (3): 188-194


    Researchers often describe the collection of repeated measurements on each individual in a study design. Advanced statistical methods, namely, mixed and marginal models, are the preferred analytic choices for analyzing this type of data.The aim was to provide a conceptual understanding of these modeling techniques.An understanding of mixed models and marginal models is provided via a thorough exploration of the methods that have been used historically in the biomedical literature to summarize and make inferences about this type of data. The limitations are discussed, as is work done on expanding the classic linear regression model to account for repeated measurements taken on an individual, leading to the broader mixed-model framework.A description is provided of a variety of common types of study designs and data structures that can be analyzed using a mixed model and a marginal model.This work provides an overview of advanced statistical modeling techniques used for analyzing the many types of correlated .data collected in a research study.

    View details for DOI 10.1097/NNR.0b013e31824f5f58

    View details for Web of Science ID 000303604500006

    View details for PubMedID 22551993

  • Teletransmitted Monitoring of Blood Pressure and Bilingual Nurse Counseling-Sustained Improvements in Blood Pressure Control During 12 Months in Hypertensive Korean Americans JOURNAL OF CLINICAL HYPERTENSION Kim, M. T., Han, H., Hedlin, H., Kim, J., Song, H. J., Kim, K. B., Hill, M. N. 2011; 13 (8): 605-612


    This paper reports the results of a clinical investigation to determine the sustainability of intervention effects to lower blood pressure (BP) that were obtained through a short-term education via home telemonitoring of BP and regular counseling by bilingual nurses during 1 year. A total of 359 middle-aged (40-64 years) Korean immigrants completed a 15-month intervention that consisted of 6-week behavioral education followed by home telemonitoring of BP and bilingual nurse telephone counseling for 12 months. The final analysis revealed a sharp increase in BP control rates sustained for more than 12 months. At baseline, only 30% of the sample achieved BP control (<140/90 mm Hg). After the initial education period (approximately 3 months), 73.3% of the participants had controlled BP levels. The levels of control were maintained and continuously improved during a 12-month follow-up period (83.2%, P<.001). These findings suggest that home telemonitoring of BP and tailored counseling are both useful tools to sustain or improve short-term education effects.

    View details for DOI 10.1111/j.1751-7176.2011.00479.x

    View details for Web of Science ID 000293349600010

    View details for PubMedID 21806771

  • Interventions that increase use of Pap tests among ethnic minority women: a meta-analysis PSYCHO-ONCOLOGY Han, H., Kim, J., Lee, J., Hedlin, H. K., Song, H., Song, Y., Kim, M. T. 2011; 20 (4): 341-351


    Although a variety of intervention methods have been used to promote Pap test screening among ethnic minority women in the US, the effectiveness of such interventions is unclear. We performed a meta-analysis to examine the overall effectiveness of these interventions in increasing Pap test use by ethnic minority women in the US.A search of databases (MEDLINE, Cumulative Index to Nursing and Allied Health Literature, PsycINFO, and Science Citation Index-Expanded) and review articles for articles published between 1984 and April 2009 identified 18 randomized and non-randomized controlled trials. The primary study outcome was the difference in the proportion of Pap tests between the treatment and comparison groups.The pooled mean weighted effect size (d) for the 18 studies was 0.158 (95% confidence interval [CI]=0.100, 0.215), indicating that the interventions were effective in improving Pap test use among ethnic minority women. Among the intervention types, access enhancement yielded the largest effect size (0.253 [95% CI=0.110, 0.397]), followed by community education (0.167 [95% CI=0.057, 0.278]) and individual counseling or letters (0.132 [95% CI=0.069, 0.195]). Combined intervention effects were significant for studies targeting Asian (0.177 [95% CI=0.098, 0.256]) and African American women (0.146 [95% CI=0.028, 0.265]), but not Hispanic women (0.116 [95% CI=-0.008, 0.240]).Pap test use among ethnic minority women is most likely to increase when access-enhancing strategies are combined. Further research is needed to determine whether more tightly controlled trials of such interventions might reveal an improved rate of cervical cancer screening in Hispanic women as well.

    View details for DOI 10.1002/pon.1754

    View details for Web of Science ID 000288860400001

    View details for PubMedID 20878847

  • Evaluation of Cumulative Lead Dose and Longitudinal Changes in Structural Magnetic Resonance Imaging in Former Organolead Workers JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL MEDICINE Schwartz, B. S., Caffo, B., Stewart, W. F., Hedlin, H., James, B. D., Yousem, D., Davatzikos, C. 2010; 52 (4): 407-414


    : We evaluated whether tibia lead was associated with longitudinal change in brain volumes and white matter lesions in male former lead workers and population-based controls in whom we have previously reported on the cognitive and structural consequences of cumulative lead dose.: We used linear regression to identify predictors of change in brain volumes and white matter lesion grade scores, using two magnetic resonance imaging scans an average of 5 years apart.: On average, total brain volume declined almost 30 cm, predominantly in gray matter. Increasing age at the first magnetic resonance imaging was strongly associated with larger declines in volumes and greater increases in white matter lesion scores. Tibia lead was not associated with change in brain volumes or white matter lesion scores.: In former lead workers in whom cumulative lead dose was associated with progressive declines in cognitive function decades after occupational exposure had ended, cumulative lead dose was associated with earlier persistent effects on brain structure but not with additional worsening during 5 years.

    View details for DOI 10.1097/JOM.0b013e3181d5e386

    View details for Web of Science ID 000276668300006

    View details for PubMedID 20357679

  • Covariate-adjusted nonparametric analysis of magnetic resonance images using Markov chain Monte Carlo STATISTICS AND ITS INTERFACE Hedlin, H., Caffo, B., Mahfoud, Z., Bassett, S. S. 2010; 3 (1): 113-123
  • A Meta-Analysis of Interventions to Promote Mammography Among Ethnic Minority Women NURSING RESEARCH Han, H., Lee, J., Kim, J., Hedlin, H. K., Song, H., Kim, M. T. 2009; 58 (4): 246-254


    Although many studies have been focused on interventions designed to promote mammography screening among ethnic minority women, few summaries of the effectiveness of the interventions are available.The aim of this study was to determine the effectiveness of the interventions for improving mammography screening among asymptomatic ethnic minority women.A meta-analysis was performed on intervention studies designed to promote mammography use in samples of ethnic minority women. Random-effects estimates were calculated for interventions by measuring differences in intervention and control group screening rates postintervention.The overall mean weighted effect size for the 23 studies was 0.078 (Z = 4.414, p < .001), indicating that the interventions were effective in improving mammography use among ethnic minority women. For mammography intervention types, access-enhancing strategies had the biggest mean weighted effect size of 0.155 (Z = 4.488, p < .001), followed by 0.099 (Z = 6.552, p < .001) for individually directed approaches such as individual counseling or education. Tailored, theory-based interventions resulted in a bigger effect size compared with nontailored interventions (effect sizes = 0.101 vs. 0.076, respectively; p < .05 for all models). Of cultural strategies, ethnically matched intervention deliveries and offering culturally matched intervention materials had effect sizes of 0.067 (Z = 2.516, p = .012) and 0.051 (Z = 2.365, p = .018), respectively.Uniform improvement in mammography screening is a goal to address breast cancer disparities in ethnic minority communities in this country. The results of this meta-analysis suggest a need for increased use of a theory-based, tailored approach with enhancement of access.

    View details for Web of Science ID 000268162700004

    View details for PubMedID 19609176

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