About

Mary D. Sammel, Sc.D., is an Emeritus Professor and the Chief of Biostatistics in the Department of Biostatistics and Epidemiology at the University of Pennsylvania Perelman School of Medicine. She serves as a Senior Scholar at the Center for Clinical Epidemiology and Biostatistics (CCEB) and is the Associate Director of Residency Research in the Department of Obstetrics and Gynecology. Additionally, she is the Director of Biostatistics at the Women’s Health Clinical Research Center and the Director of Biostatistics for Penn PROMOTES Research on Sex and Gender in Health. Her research expertise focuses on biostatistics, with significant contributions to the understanding of covariance misspecification in latent variable models, genetic polymorphisms associated with preterm premature rupture of membranes, and the influence of genetic and hormonal factors on reproductive health. Dr. Sammel's work includes investigating racial differences in hormone levels and reproductive symptoms, as well as exploring the biological and statistical aspects of women's health. Her academic background includes a B.A. and M.A. in Statistics from the University of Michigan and an Sc.D. in Biostatistics from Harvard School of Public Health.

Research topics

• Sociology
• Medicine
• Gerontology
• Surgery
• Psychology
• Obstetrics
• Gender studies
• Emergency medicine
• Medical education
• Pediatrics

Selected publications

• Menopause in the All of Us Research Program: A Descriptive Summary of Electronic Health Record and Survey Response across Sociodemographic Characteristics

  medRxiv · 2026-04-25

  articleOpen access

  ABSTRACT Objective Menopause is a significant physiological transition with implications for health outcomes (e.g., cardiometabolic), yet gaps remain in understanding the menopause transition, including how menopause timing and type influence health outcomes. Large-scale cohort studies in midlife (age∼40-60) females, including the All of Us Research Program (AoURP), provide opportunities to study menopause across diverse populations and data modalities. We characterized menopause-related data in AoURP, focusing on age distributions and concordance between EHR diagnosis codes and self-reported survey responses. Methods We analyzed menopause-related survey, EHR diagnostic code, and genomic data among ∼396,000 participants in AoURP with female sex. We summarized menopause data across modalities, overlap between survey, EHR, and genomic data, and age distributions overall and across sociodemographic characteristics. Results Among ∼396,000 females, surveys captured ∼193,000 menopause observations, nearly seven times more than structured EHR diagnoses (∼28,000), suggesting under-ascertainement in EHR data. Nearly all females (∼99%) with an EHR menopause diagnosis also reported menopause in the survey. Approximately 22,000 participants had intersected EHR, survey, and genomic menopause-related data. Survey-based age patterns matched expectations, with participants <40 years predominantly reporting pre-menopausal status and those >60 years predominantly reporting post-menopausal status. A small subset (N≈1,700; 4%) (age>70 years) reported no menopause, suggesting response or recall bias. EHR menopause codes were concentrated after age>45 years, with a notable spike at age 65. Modest differences in survey-based menopause age distributions were observed by sociodemographic characteristics (e.g., race, ancestry). Conclusions These findings inform sampling strategies, power calculations, phenotype definition, and study design for menopause research using AoURP.

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• Sperm sncRNA networks are synchronized by a coordination between adverse childhood experiences (ACE) and current stress

  Scientific Reports · 2026-04-17

  articleOpen access

  While stress in the environment alters sperm function and fertility, the underlying biology is not understood. Our prior studies showed that current stress could significantly change the composition and levels of sperm small noncoding (sncRNA) and impact sperm motility in men. However, the additional influence of adversity experienced earlier in life, designated as adverse childhood experiences (ACE), on sperm sncRNA dynamics remains unclear. To expand our understanding of the important relationship between ACE and stress, we recruited a longitudinal human cohort and modeled differential sncRNA and co-expression networks associated with perceived stress and ACE. Utilizing a repeated measures design, we were able to identify significant time-dependent interactions between ACE and perceived stress that resulted in differential sncRNA expression. Furthermore, network analyses revealed ACE and perceived stress coordinated sncRNA across subtypes, including miRNA that target genes important for offspring development. As these changes were identified widely across sncRNA subtypes, our findings reflect a novel and exciting synchronization strategy by which current and past experiences can impact the next generation. Evolutionarily, this coordination would preserve sncRNA modules essential for species survival while allowing refinement around developmental pathways important for intergenerational fitness.

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• Beyond One Size Fits All: Identifying Distinct Resilience Profiles in Spinal Cord Injury

  Topics in Spinal Cord Injury Rehabilitation · 2026-01-01

  articleOpen access

  Background: Resilience plays a critical role in adaptation following spinal cord injury (SCI), yet there is no consensus on how resilience is defined or measured. Current unidimensional approaches may miss important patterns in resilience responses that could inform targeted interventions. Objectives: To identify distinct subgroups of individuals with SCI based on resilience patterns using latent class analysis (LCA) and examine their associations with demographic, injury-related, and psychosocial factors. Methods: We conducted a cross-sectional analysis of 10,634 adults with SCI from the National SCI Model System Database who completed the Spinal Cord Injury-Quality of Life Resilience short form (SCI-QOL-R-SF) between 2016 and 2021. LCA identified response patterns across the 8 SCI-QOL-R-SF items. Polytomous logistic regression examined factors related to class membership. Linear regression assessed relationships between resilience classes and life satisfaction and depression symptoms. Results: A 3-class solution provided optimal fit: high resilience (40.5%), medium resilience (38.4%), and low resilience (21.1%). Classes demonstrated a clear gradient pattern of responses from "always" to "sometimes" on the SCI-QOL items. Significant predictors of class membership included sex, age, employment status, self-care behaviors, health status, time since injury, and social support. Resilience class was the strongest predictor of both life satisfaction (accounting for 14% of variance) and depression symptoms (12.2% of variance), with large effect sizes between classes. Conclusion: Distinct resilience patterns exist among individuals with SCI and strongly predict psychosocial outcomes. These findings support tailored interventions targeting specific resilience profiles to improve life satisfaction and reduce depression in this population.

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• SUN-126 Fasting Total Ghrelin and Hunger Differ Across Sex and Gender in Adults: A Cross-Sectional Study

  Journal of the Endocrine Society · 2025-10-01

  articleOpen access

  Abstract Disclosure: J. Taormina: None. M. Bolt: None. M. Cornier: None. K.L. Moreau: None. M.E. Wierman: None. M.S. Rothman: None. K.T. Legget: None. J.R. Tregellas: None. A.K. Hild: None. D.B. Hammond: None. A. Gebregzabheir: None. M.P. Mancuso: None. M.D. Sammel: None. S.J. Iwamoto: None. Introduction: Plasma ghrelin is central to homeostatic control of hunger and is inversely correlated with total body weight and body fat percentage (BF%). Cisgender (cis) women have higher plasma ghrelin than cis men, and ghrelin is positively associated with serum estradiol in cis women and testosterone in cis men. Estradiol-based gender-affirming hormone therapy (GAHT) use in transgender (trans) women and testosterone-based GAHT use in trans men are associated with body weight increases and differential body composition changes. The association of GAHT with fasting total ghrelin and hunger in trans adults is understudied and may suggest one mechanism for weight and body composition changes observed with GAHT. Specific aim: To evaluate differences in fasting total ghrelin and hunger in adults across sex and gender. Hypothesis: Fasting total ghrelin and hunger are more similar by sex than by gender. Methods: Nonsmoking trans adults on GAHT for >1 year (no gonadectomy) and cis adults (no hypogonadism) participated in a cross-sectional study with fasting total ghrelin and insulin measurements, appetite-related questionnaires (visual analog scale [VAS] for hunger and satiety; Food Cravings Questionnaire-State Version [FCQ-S]), and dual-energy x-ray absorptiometry to measure BF%, after an overnight fast. Multivariable linear regression models examined differences between groups while adjusting for pre-specified covariates (age, BF%, fasting insulin). Results: Among 110 mostly white, non-Hispanic adults (48 cis women, 12 cis men, 34 trans women, 16 trans men), mean (±SD) ages were 39 (10), 39 (10), 44 (17) and 30 (8) years; mean BF% were 43 (4), 30 (4), 35 (8) and 30 (7) %; and mean fasting insulin levels (reference 0-20 uIU/mL) were 15 (7), 18 (9), 6 (4) and 4 (3) uIU/mL, respectively. In regression modeling, fasting total ghrelin was different in trans women (by -341.7 pg/mL, 95% CI [-520.1, -163.3], p < 0.001) and cis men (by -306.0 pg/mL, 95% CI: [-561.1, -51.0], p = 0.02) compared to cis women. Trans women, trans men, and cis men had similar ghrelin levels. Hunger VAS was different for all groups compared to cis women (trans men by -17.9 mm, 95% CI: [-34.9, -0.9], p = 0.04; trans women by -25.9 mm, 95% CI: [-38.3, -13.4], p < 0.001; cis men by -21.5 mm, 95% CI: [-39.4, -3.6], p = 0.02). Trans women, trans men and cis men had similar hunger VAS. Trans and cis adults scored similarly on satiety VAS and FCQ-S. Conclusions: Among trans women, lower fasting total ghrelin and hunger compared to cis women may be attributed to sex recorded at birth rather than estradiol-based GAHT use. Testosterone-based GAHT use may decrease hunger behavior but not fasting total ghrelin compared to pre-GAHT baseline. Future prospective studies can elucidate the impacts of sex recorded at birth, gender, and sex hormones on these and other hormonal and behavioral factors responsible for appetite regulation. Presentation: Sunday, July 13, 2025

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• Invisible Scars: Residual Consequences of Childhood Maltreatment Even in Adults Classified as Resilient

  Child Maltreatment · 2025-10-27

  article

  People exposed to childhood maltreatment (CM) are thought to emerge as "resilient" or "non-resilient" in adulthood, with the implication that resilient adults eluded the negative consequences of CM. However, adults with CM who are classified as "resilient" may still face negative outcomes in areas of life not captured by resilience criteria. To test this hypothesis, the present study examined whether higher levels of CM were associated with worse psychological, social, and physical health outcomes even in "resilient" adults. Using data at all three survey waves spanning two decades from the Midlife in the United States (MIDUS) longitudinal study, resilience was defined as healthy functioning across seven domains: psychiatric disorders, substance use, education, employment, homelessness, crime, and social isolation. Results showed that in both the "resilient" and "non-resilient" groups, higher CM exposure was significantly associated with worse outcomes on measures of stress reactivity, perceived stress, number of chronic conditions, self-esteem, life satisfaction, relationship quality with friends and family, and positive relations with others (measured at wave 3; all p-values <.033). These findings suggest that CM has enduring and overlooked psychological, social, and physical health consequences not captured by comprehensive resilience criteria, highlighting the need for intervention even in seemingly resilient adults.

  PublisherDOI

• The effect of air pollution exposure on menstrual cycle health using self-reported data from a mobile health app: a prospective, observational study

  The Lancet Planetary Health · 2025-05-01 · 4 citations

  articleOpen access

  Background Toxicological evidence suggests that ambient air pollution has endocrine-disrupting properties that can affect menstrual cycle functioning, which represents an important marker of women's reproductive health.We aimed to estimate the effect of short-term and long-term PM 25 exposure on menstrual cycle outcomes across the USA, Brazil, and Mexico using self-reported data from a mobile health app.Methods For this prospective observational study, we collected de-identified self-reported data from the Clue mobile health app, in which users self-tracked menstruation cycles.For the current study, eligible participants were aged 18-44 years, were not using hormonal birth control, and lived in one of 230 cities in the USA, Mexico, or Brazil.The primary outcome of interest at the city level was the proportion of menstrual cycles with abnormally short length (<24 days) and long length (>38 days) of all cycles recorded.The primary outcome at the cycle level was a binary indicator: abnormal cycle length (<24 days or >38 days) or not (normal cycle length).We used regression analyses to evaluate associations between long-term PM 25 concentrations (mean concentration between 2016 and 2020) and the city-level outcomes after controlling for potential confounders.Conditional logistic regression models were used to evaluate associations between cycle-specific PM 25 and if a cycle was of abnormal length within an individual in the dataset, after controlling for time-varying factors. FindingsBetween Jan 1, 2016 and Dec 31, 2020, 92 550 app users residing in 230 cities across the USA, Brazil, and Mexico provided data corresponding to 2 220 281 menstrual cycles, and were included in our main cohort.A significant association was observed between long-term PM 25 exposure and the proportion of menstrual cycles of abnormally long or short duration (odds ratio [OR] 1023 [95% CI 1013-1033]) and the proportion of cycles that were specifically abnormally long (OR 1036 [1023-1049]) for every 10 g/m increase in PM 25 .No associations were identified between short-term PM 25 concentrations and abnormal cycle length.Interpretation These findings suggest that PM 25 exposure affects menstrual cycle outcomes.More research is needed to better elucidate the biological mechanisms through which PM 25 affects the menstrual cycle.

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• Serum Protein Dynamics in Early Pregnancy Loss Management: Findings from the PreFaiR Trial

  Research Square · 2025-09-25

  preprintOpen access
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• ARE YOU THE ONE? SELECTING THE BEST EMBRYO FOR FROZEN EMBRYO TRANSFER

  Fertility and Sterility · 2025-06-29

  articleOpen access
  PublisherOA PDFDOI

• Sex Hormone Replacement Therapy and Bleeding Patterns among Adolescents and Young Adult Females with Prader–Willi Syndrome

  Journal of Pediatric and Adolescent Gynecology · 2025-08-07

  article
  PublisherDOI

• Measuring associations between hormonal entropy, the prevalence of vasomotor symptoms, and menstrual dynamics

  American Journal of Physiology-Endocrinology and Metabolism · 2025-09-23 · 1 citations

  articleOpen access

  There are a number of strong associations between the regularity/complexity of urinary sex hormones (being formalized via fuzzy and distribution entropy) and vasomotor symptoms (VMS). Standardized metrics of hormonal regularity (i.e., hormonal entropy) show promise in being used to identify different hormonal profiles underlying VMS occurrence, to provide a general gauge of reproductive aging, and to help predict the overall character of VMS experiences for the remainder of the menopause transition and beyond.

  PublisherDOI

Recent grants

• NIH Grant P50MH099910

  NIH · $13.0M · 2019

Frequent coauthors

• Kurt T. Barnhart

  University of Pennsylvania

  445 shared

• Hao Huang

  Beijing Jiaotong University

  385 shared

• Jay D. Iams

  Eunice Kennedy Shriver National Institute of Child Health and Human Development

  353 shared

• Monica Longo

  336 shared

• Suhas G. Kallapur

  University of California, Los Angeles

  324 shared

• Alan H. Jobe

  Cincinnati Children's Hospital Medical Center

  324 shared

• Anthony Sciscione

  323 shared

• Amy Turitz

  Greenwich Hospital

  322 shared

Labs

• Biostatistics and EpidemiologyPI

Education

• Post-Doctoral Fellow, Biostatistics

  Harvard University

  1997

• ScD, Biostatistics

  Harvard University

  1995

• MA, Statistics

  University of Michigan

  1988

• BA, Statistics

  University of Michigan

  1986