Normal Curves: Sexy Science, Serious Statistics

Could a preteen vaccine wipe out a global cancer? In this episode, we examine the bold claim that cervical cancer could be eradicated in much of the world by the end of the century—thanks to the highly effective HPV vaccine. We unpack statistical modeling, microsimulations, and how Markov chains make good date-night conversation. We also explore why vaccine uptake has been uneven, how a splash of vinegar is helping screen for cancer in low-resource countries, and why HPV isn’t just a women’s issue—it now causes more cancer in men than in women. Plus: dangerously tight corsets, allegedly breast-squeezing nuns, and the Cosmo quote we wish we’d written ourselves.Statistical topics:Cancer surveillanceMarkov modelsMicrosimulation modelsSensitivity analysesPassive surveillanceBackground ratesCase reports and case seriesMethodologic morals:“When reality is too complex to test, let microsimulations do the rest.”“Case reports are medicine's equivalent to see something, say something. They call for hard data, not hysteria.”Citations:No cervical cancer cases detected in vaccinated women following HPV immunisation. University of Strathclyde, January 22, 2024.Palmer TJ, Kavanagh K, Cuschieri K, et al. Invasive cervical cancer incidence following bivalent human papillomavirus vaccination: a population-based observational study of age at immunization, dose, and deprivation. J Natl Cancer Inst. 2024;116:857-65.Rigoni-Stern. Statistical facts about cancers on which Doctor Rigoni-Stern based his contribution to the Surgeons' Subgroup of the IV Congress of the Italian Scientists on 23 September 1842. (translation). Stat Med. 1987;6:881-4.Gordan JA, Lenkei SC. Cleanliness, Continence, Constancy, and Cervical Carcinoma. Can Med Assoc J. 1964;90:1132.zur Hausen H. Condylomata acuminata and human genital cancer. Cancer Res. 1976;36:794.Walboomers JM, Jacobs MV, Manos MM, et al. Human papillomavirus is a necessary cause of invasive cervical cancer worldwide. J Pathol. 1999;189:12-9.Chesson HW, Dunne EF, Hariri S, et al. The estimated lifetime probability of acquiring human papillomavirus in the United States. Sex Transm Dis. 2014;41:660-4.Sullivan, Morgan. Let’s Have a Little Chat About the HPV Vaccine. Cosmopolitan. March 19, 2025.Burger EA, Kim JJ, Sy S, et al. Age of Acquiring Causal Human Papillomavirus (HPV) Infections: Leveraging Simulation Models to Explore the Natural History of HPV-induced Cervical Cancer. Clin Infect Dis. 2017;65:893-99.Canfell K. Towards the global elimination of cervical cancer. Papillomavirus Res. 2019;8:100170.World Health Organization. Global strategy to accelerate the elimination of cervical cancer as a public health problem. November 17, 2020.Hall MT, Simms KT, Lew JB, et al. The projected timeframe until cervical cancer elimination in Australia: a modelling study. Lancet Public Health. 2019;4:e19-e27.Burger EA, Smith MA, Killen J, et al. Projected time to elimination of cervical cancer in the USA: a comparative modelling study. Lancet Public Health. 2020 Apr;5(4):e213-e222.Brisson M, Kim JJ, Canfell K, et al. Impact of HPV vaccination and cervical screening on cervical cancer elimination: a comparative modelling analysis in 78 low-income and lower-middle-income countries. Lancet. 2020;395:575-90.Escabí-Wojna E, Alvelo-Fernández PM, Suárez E, et al. Sex differences in parental reasons for lack of intent to initiate HPV vaccination among adolescents ages 13-17 years: National Immunization Survey - Teen 2019-2021. Vaccine. 2025;44:126584. (see supplement) Szilagyi PG, Albertin CS, Gurfinkel D, et al. Prevalence and characteristics of HPV vaccine hesitancy among parents of adolescents across the US. Vaccine. 2020;38:6027-6037.LaPook, Jonathan. Is the HPV Vaccine Safe? CBS Evening News. August 18, 2009.Slade BA, Leidel L, Vellozzi C, et al. Postlicensure safety surveillance for quadrivalent human papillomavirus recombinant vaccine. JAMA. 2009;302:750-7.Kharabsheh S, Al-Otoum H, Clements J, et al. Mass psychogenic illness following tetanus-diphtheria toxoid vaccination in Jordan. Bull World Health Organ. 2001;79:764-70.Jones TF, Craig AS, Hoy D, et al. Mass psychogenic illness attributed to toxic exposure at a high school. N Engl J Med. 2000;342:96-100.Buttery JP, Madin S, Crawford NW, et al. Mass psychogenic response to human papillomavirus vaccination. Med J Aust. 2008;189:261-2.Clements CJ. Gardasil and mass psychogenic illness. Aust N Z J Public Health. 2007;31:387.Simas C, Munoz N, Arregoces L, et al. HPV vaccine confidence and cases of mass psychogenic illness following immunization in Carmen de Bolivar, Colombia. Hum Vaccin Immunother. 2019;15:163-66.Larson HJ. Japan's HPV vaccine crisis: act now to avert cervical cancer cases and deaths. Lancet Public Health. 2020;5:e184-e185.Brinth LS, Pors K, Theibel AC, Mehlsen J. Orthostatic intolerance and postural tachycardia syndrome as suspected adverse effects of vaccination against human papilloma virus. Vaccine. 2015;33:2602-5.Large well-done studies following up on case reports and passive surveillance:Phillips A, Hickie M, Totterdell J, Brotherton J, Dey A, Hill R, Snelling T, Macartney K. Adverse events following HPV vaccination: 11 years of surveillance in Australia. Vaccine. 2020;38:6038-46.Arnheim-Dahlström L, Pasternak B, Svanström H, et al.

Today’s deep dive: the surprisingly serious science of penis size. Using self-report surveys, objective measurements, and a healthy dose of old-school statistics, we ask: How do you get clean data on gentlemen’s goods?Along the way, we explore social desirability bias, survey design tricks, and what happens when science meets insecurity. You’ll never look at a Starbucks cup the same way again.Statistical topicsSocial desirability biasSelection biasVolunteer BiasDescriptive StatisticsRight-Skewed DistributionsStrategies to improve accuracy in self-report dataMethodological morals“When answers aim to please, truth takes its leave.”“Without descriptive statistics, you'll never know if you measure up.”ReferencesCROWNE DP, MARLOWE D. A new scale of social desirability independent of psychopathology. J Consult Psychol. 1960;24:349-354. doi:10.1037/h0047358Gebhard, P.H. and Johnson, A.B., 1998. The Kinsey data: Marginal tabulations of the 1938-1963 interviews conducted by the Institute for Sex Research. Indiana University Press.Herbenick D, Reece M, Schick V, Sanders SA. Erect penile length and circumference dimensions of 1,661 sexually active men in the United States. J Sex Med. 2014;11(1):93-101. doi:10.1111/jsm.12244Johnston, L., McLellan, T., & McKinlay, A. (2014). (Perceived) size really does matter: Male dissatisfaction with penis size. Psychology of Men & Masculinity, 15(2), 225–228. https://doi.org/10.1037/a0033264King BM. The Influence of Social Desirability on Sexual Behavior Surveys: A Review. Arch Sex Behav. 2022;51(3):1495-1501. doi:10.1007/s10508-021-02197-0King BM. Average-Size Erect Penis: Fiction, Fact, and the Need for Counseling. J Sex Marital Ther. 2021;47(1):80-89. doi:10.1080/0092623X.2020.1787279King BM, Duncan LM, Clinkenbeard KM, Rutland MB, Ryan KM. Social Desirability and Young Men's Self-Reports of Penis Size. J Sex Marital Ther. 2019;45(5):452-455. doi:10.1080/0092623X.2018.1533905Larson, R.B., 2019. Controlling social desirability bias. International Journal of Market Research, 61(5), pp.534-547.Stodel, M. (2015). But What Will People Think?: Getting beyond Social Desirability Bias by Increasing Cognitive Load. International Journal of Market Research, 57(2), 313-322. https://doi.org/10.2501/IJMR-2015-024   (Original work published 2015)Spreadsheet with Penis Length DataOur online courses and programs: Demystifying Data: A Modern Approach to Statistical Understanding  Clinical Trials: Design, Strategy, and Analysis Medical Statistics Certificate Program  Writing in the Sciences Epidemiology and Clinical Research Graduate Certificate Program Find us on social:Kristin -  LinkedIn & Twitter/XRegina - LinkedIn & ReginaNuzzo.com(00:00) - Introduction (02:33) - Starbucks metric and episode themes (07:17) - Men and women’s sampling frames (09:24) - Kinsey and his studies (14:59) - Statistics quiz on Kinsey penis data (22:13) - Social desirability bias (29:20) - Cognitive tricks to elicit honest survey answers (35:13) - Condoms, honest penis lengths, and another stats quiz (41:33) - Objective penis appraisers, measurement error, and reliability (46:45) - Whose penises? Volunteer and selection bias (50:30) - Mini-meta-analysis and the “answer” (52:09) - Wrap-up and methodological morals

Wrinkles and sagging skin—just normal aging, or can you blame your sweet tooth? We dive into “sugar sag,” exploring how sugar, processed foods, and even your crispy breakfast toast might be making you look older than if you’d said no to chocolate cake and yes to broccoli. Along the way, we encounter statistical adjustment, training and test data sets, what we call “references to nowhere,” plus some cadavers and collagen. Ever heard of an AGE reader? Find out how this tool might offer a sneak peek at your date’s age—and maybe even a clue about his… um… “performance.”Statistical topics Training and test setsStatistical adjustmentOverfitting PlagiarismProper citing practicesReferences to nowhereMethodologic morals“When you plagiarize, you steal the errors too.”“Overdone statistical adjustment is like overdone photo filters–at a certain point it’s just laughable.”CitationsCollagen turnover: Verzijl N, DeGroot J, Thorpe SR, et al.Effect of Collagen Turnover on the Accumulation of Advanced Glycation End Products. JBC. 2000;275:39027-31.Cadaver study:Hamlin CR, Kohn RR, Luschin JH. Apparent Accelerated Aging of Human Collagen in Diabetes Mellitus. Diabetes. 1975; 24: 902–904.AGE ReaderStudies of AGEs and diabetes and health:Monnier VM, Cerami A. Nonenzymatic browning in vivo: possible process for aging of long-lived proteins. Science. 1981;211:491-3. Brownlee M, Vlassara H, Cerami A. Nonenzymatic glycosylation and the pathogenesis of diabetic complications. Ann Intern Med. 1984;101:527-37. Monnier VM, Vishwanath V, Frank KE, et al. Relation between Complications of Type I Diabetes Mellitus and Collagen-Linked Fluorescence. N Engl J Med. 1986;314:403-408.Monnier VM, Sell DR, Abdul-Karim FW, et al. Collagen browning and cross-linking are increased in chronic experimental hyperglycemia. Relevance to diabetes and aging. Diabetes. 1988;37:867-72. Monnier VM, Bautista O, Kenny D, et al. Skin collagen glycation, glycoxidation, and crosslinking are lower in subjects with long-term intensive versus conventional therapy of type 1 diabetes: relevance of glycated collagen products versus HbA1c as markers of diabetic complications. Diabetes 1999; 48: 870–80.Genuth S, Sun W, Cleary P, et al. Glycation and carboxymethyllysine levels in skin collagen predict the risk of future 10-year progression of diabetic retinopathy and nephropathy in the diabetes control and complications trial and epidemiology of diabetes interventions and complications participants with type 1 diabetes. Diabetes. 2005;54:3103-11. van Waateringe RP, Slagter SN, van Beek AP, et al. Skin autofluorescence, a non-invasive biomarker for advanced glycation end products, is associated with the metabolic syndrome and its individual components. Diabetol Metab Syndr. 2017;9:42. Kouidrat Y, Zaitouni A, Amad A, et al. Skin autofluorescence (a marker for advanced glycation end products) and erectile dysfunction in diabetes. J Diabetes Complications. 2017;3:108-113. Fujita N, Ishida M, Iwane T, et al. Association between Advanced Glycation End-Products, Carotenoids, and Severe Erectile Dysfunction. World J Mens Health. 2023;41:701-11. Uruska A, Gandecka A, Araszkiewicz A, et al. Accumulation of advanced glycation end products in the skin is accelerated in relation to insulin resistance in people with Type 1 diabetes mellitus. Diabet Med. 2019;36:620-625. Boersma HE, Smit AJ, Paterson AD, et al. Skin autofluorescence and cause-specific mortality in a population-based cohort. Sci Rep 2024;14:19967.Review article with conflicts of interest: Draelos ZD. Sugar Sag: What Is Skin Glycation and How Do You Combat It? J Drugs Dermatol. 2024; 23:s5-10.Clinical study on AGE interrupter cream:Draelos ZD, Yatskayer M, Raab S, Oresajo C. An evaluation of the effect of a topical product containing C-xyloside and blueberry extract on the appearance of type II diabetic skin. J Cosmet Dermatol. 2009;8:147-51. The citation trail:2023 review article: Zgutka K, Tkacz M, Tomasiak, et al. A Role for Advanced Glycation End Products in Molecular Ageing. Int J Mol Sci. 2023; 24: 9881. Sentence: “Interestingly, strict control of blood sugar for 4 months reduced the production of glycosylated collagen by 25%, and low-sugar food prepared by boiling could also reduce the production of AGEs [152].”Reference 152 is a review article: Cao C, Xiao Z, Wu Y, et al. Diet and Skin Aging-From the Perspective of Food Nutrition. Nutrients. 2020;12:870. Sentence: “However, strict control of blood sugar for four months can reduce the production of glycosylated collagen by 25%, and low-sugar food prepared by boiling can also reduce the production of AGEs [93–95].”Reference 93 is a review article: Nguyen HP, Katta R. Sugar sag: Glycation and the role of diet in aging skin. Skin Ther Lett. 2015; 20: 1–5. Sentence: “Tight glycemic control over a 4-month period can result in a reduction of glycated collagen formation by 25%.37,38”Reference 94 and 38 is a review article: Draelos ZD. Aging skin: the role of diet: facts and controversies. Clin Dermatol. 2013;31:701-6. Sentence: “Tighter glycemic control can reduce glycated collagen by 25% in 4 months.” No citation given.Reference 95 and 37 is a review article: Danby FW. Nutrition and aging skin: Sugar and glycation. Clin. Dermatol. 2010;28: 409–11. Sentence: “...tight glycemic control can drop glycated collagen formation by 25% in 4 months.” No citation given.The origi...

What if you could treat your prediabetes with . . . worms? Regina and Kristin dive into a surprising early-phase clinical trial on hookworm therapy—that’s right, intentionally infecting yourself with parasitic worms—to treat metabolic conditions. They dig into the biological rationale (inflammation, abdominal fat, and gut immunology), the clever study design (hello, Tabasco sauce!), and the statistical chops behind this phase 1B trial (block randomization, missing data, and nonparametric hypothesis tests).  Along the way, expect self-experimenting scientists, worm sex, poop analysis, and the world’s nerdiest aphrodisiac: a well-documented protocol. Statistical topicsRandomized controlled trial (RCT)Primary and secondary outcomesPlacebos, placebo effect, and nocebo effectBlock randomizationSample sizeDouble-blindingMissing data protocolsReproducible researchNonparametric hypothesis testingKruskal-Wallis testMethodological morals“Walk before you can run. Invest in simple but high-quality Phase I clinical trials.”“When faced with small samples, you better rank and sum, baby.”ReferencesPierce DR, McDonald M, Merone L, et al. Effect of experimental hookworm infection on insulin resistance in people at risk of type 2 diabetes. Nat Commun. 2023;14(1):4503. doi:10.1038/s41467-023-40263-4Nuzzo, R. What Happens When Scientists Experiment on Themselves? Reader’s Digest. Updated April 16, 2016.Ethics of self-experimentation Helminthic Therapy Wiki Pritchard D. Worming your way to good health [video online]. TEDx Talks. Published November 19, 2013. https://www.youtube.com/watch?v=sm5DcdZbnGAChapman PR, Giacomin P, Loukas A, McCarthy JS. Experimental human hookworm infection: a narrative historical review. PLoS Negl Trop Dis. 2021;15(12):e0009908. doi:10.1371/journal.pntd.0009908Sobotková K, Parker W, Levá J, Růžková J, Lukeš J, Jirků Pomajbíková K. Helminth Therapy - From the Parasite Perspective. Trends Parasitol. 2019;35(7):501-515. doi:10.1016/j.pt.2019.04.009Zatterale F, Longo M, Naderi J, et al. Chronic Adipose Tissue Inflammation Linking Obesity to Insulin Resistance and Type 2 Diabetes. Front Physiol. 2020;10:1607. Published 2020 Jan 29. doi:10.3389/fphys.2019.01607Kristin and Regina’s online coursesDemystifying Data: A Modern Approach to Statistical Understanding  Clinical Trials: Design, Strategy, and Analysis Medical Statistics Certificate Program  Writing in the Sciences Epidemiology and Clinical Research Graduate Certificate Program Program we teach in:Epidemiology and Clinical Research Graduate Certificate Program Find us on:Kristin -  LinkedIn & Twitter/XRegina - LinkedIn & ReginaNuzzo.com(02:44) - What happens when scientists experiment on themselves (06:56) - Mail-order DIY helminthic therapy (09:26) - Hookworm biology (15:53) - Inflammation, abdominal fat, immune system, and hookworms (22:26) - Hookworm therapy clinical trial design (26:57) - Clinical trial phases deep dive (32:21) - Interesting placebos (sham surgeries and psychedelics) (38:30) - Excitement over hookworm trial open data and data protocols (45:42) - Hookworm trial results (49:45) - Mood and well-being with hookworms (54:23) - Effects of hookworms on weight (57:06) - Nonparametric tests and how they work (01:03:53) - What the participants did after the study (01:05:50) - Wrap-up

Does a daily glass of wine really keep the cardiologist away? It’s a claim we’ve all heard: light to moderate drinking is good for your heart. But is it science or just a convenient excuse for happy hour? In this episode, we dive into the history behind this claim, discuss the challenges of observational studies and statistical adjustment, and explore attempts at randomized trials and natural experiments to get to the bottom of this boozy debate. Grab your drink—or maybe don’t—and join us! Statistical topicsStatistical AdjustmentRegressionResidual and Unmeasured ConfoundingRandomized TrialsMultiple TestingOutcome SwitchingMendelian Randomization Methodological morals“Statistical adjustment cannot erase all confounding.”“When you can’t experiment on people, let Nature experiment on people.”CitationsAlcohol and Drinking. Gallup Poll. 2024. Canada’s Guidance on Alcohol and Health. Canadian Centre on Substance Use and Addiction. 2023.  U.S. Department of Agriculture and U.S. Department of Health and Human Services. 2020 – 2025 Dietary Guidelines for Americans. 2020.U.S. Department of Agriculture and U.S. Department of Health and Human Services. Alcohol and Cancer Risk: The US Surgeon General's Advisory. 2025.Mezue K, Osborne MT, Abohashem S, et al. Reduced stress-related neural network activity mediates the effect of alcohol on cardiovascular risk. JACC. 2023;81:2315-25.McPhillips D, Goodman B. Small amounts of alcohol may turn down stress in the brain, benefiting the heart, new study finds. CNN. June 12, 2023.Friedman GD, Klatsky AL. Is alcohol good for your health? NEJM. 1993;329:1882-3.Sainani K. Alcohol and Weight. Allure. July 14, 2010.Wang LU, Lee IM, Manson JE, et al. Alcohol consumption, weight gain, and risk of becoming overweight in middle-aged and older women. Arch Intern Med. 2010;170:453-61.Sainani K. Drinking and Weight. Allure. Oct 31, 2008.Tolstrup JS, Halkjær J, Heitmann BL, et al. Alcohol drinking frequency in relation to subsequent changes in waist circumference. Am J Clin Nutr. 2008;87:957-63.Rabin RC. Major Study on Drinking Will be Shut Down. New York Times. June 15, 2018.Mitchell G, Lesch M, McCambridge J. Alcohol industry involvement in the moderate alcohol and cardiovascular health trial. AJPH. 2020;110:485-8.Gepner Y, Golan R, Harman-Boehm I, et al. Effects of Initiating Moderate Alcohol Intake on Cardiometabolic Risk in Adults With Type 2 Diabetes: A 2-Year Randomized, Controlled Trial. Ann Intern Med. 2015;163:569-79.Slade E, Drysdale H, Goldacre B, et al. Discrepancies between prespecified and reported outcomes. Ann Intern Med. 2016;164:374.Biddinger KJ, Emdin CA, Haas ME, et al. Association of habitual alcohol intake with risk of cardiovascular disease. JAMA Netw Open. 2022;5:e223849.Page with more details on the CASCADE trial Kristin and Regina’s online courses: Demystifying Data: A Modern Approach to Statistical Understanding  Clinical Trials: Design, Strategy, and Analysis Medical Statistics Certificate Program  Writing in the Sciences Epidemiology and Clinical Research Graduate Certificate Program Program that we teach in:Epidemiology and Clinical Research Graduate Certificate Program Find us on:Kristin -  LinkedIn & Twitter/XRegina - LinkedIn & ReginaNuzzo.com(00:00) - Introduction (03:00) - Drinking habits in America (04:13) - New Canadian drinking guidelines (07:51) - Definition of light-to-moderate drinking (08:43) - Risks and benefits of light-to-moderate drinking (11:37) - History of the heart health claim (18:34) - Problems with observational studies (23:37) - Statistical adjustment (26:36) - Residual and unmeasured confounding (32:16) - Overconfidence in observational studies (36:13) - Randomized trials of alcohol (37:29) - Canceled NIH randomized trial of alcohol (42:39) - The CASCADE randomized trial of wine (44:15) - The problem of multiple testing (48:53) - Outcome switching (50:29) - Mendelian randomization (01:00:01) - Mendelian randomization studies of alcohol and heart disease (01:04:06) - Wrap-up

Wear red and drive men wild with lust – or so says scientific research on color’s role in human mating. But can a simple color swap really boost a woman’s hotness score? In this episode, we delve into the evidence behind the Red Dress Effect, from a controversial first study in college men to what the latest research says about who this trick might work for (and who it might not). Along the way we encounter red monkey butts, old-Internet websites, the Winner’s Curse in scientific research, adversarial collaborations, and why size (ahem, sample size) really does matter. Statistical topicsReproducibility crisis in psychologySample sizeSelection biasWinner’s curseCohen’s d standardized effect sizeAdversarial collaborationMeta-analysisPreregistrationPublication biasStatistical moderatorsMethodological morals“The smaller the sample, the flashier the result, the less you should trust it.”“Good scientists learn from their statistical mistakes and fix them.”ReferencesClarke, G. How to Be Sexy: 7 Weird (But True) Rules of Attraction. Allure. January 23, 2013.Nuzzo, R. Vying for a soul mate? Psych out the competition with science. Los Angeles Times. December 8, 2008. Vying for a Soul Mate on the Today Show, December 30, 2008.Elliot, A.J. and Niesta, D. Romantic red: red enhances men's attraction to women.  Journal of personality and social psychology. 2008; 95: 1150 – 1164. Lehrer, J. The Truth Wears Off. The New Yorker, December 5, 2010. MacMahon, B., Yen, S., Trichopoulos, D., Warren, K. and Nardi, G. Coffee and cancer of the pancreas. New England Journal of Medicine. 1981; 304: 630-633.Ioannidis, J.P. Why most published research findings are false. PLoS medicine. 2005; 2(8), e124 Lehmann, G.K., Elliot, A.J. and Calin-Jageman, R.J. Meta-analysis of the effect of red on perceived attractiveness. Evolutionary Psychology. 2018; 16: 1474704918802412. Pazda, A.D., Thorstenson, C.A. and Elliot, A.J. The effect of red on attractiveness for highly attractive women. Curr Psychol. 2023; 42: 8066–8073Kristin and Regina’s online courses: Demystifying Data: A Modern Approach to Statistical Understanding  Clinical Trials: Design, Strategy, and Analysis Medical Statistics Certificate Program  Writing in the Sciences Epidemiology and Clinical Research Graduate Certificate Program Chapters(00:00) - Introduction (06:04) - Red Dress Effect on TV (10:01) - Red Monkey Butts (12:56) - 2008 Study on Romantic Red (16:04) - HotOrNot.com (20:10) - 2008 Study Results (26:07) - Cohen’s d Standardized Effect Size (31:49) - Problems with Small Sample Sizes (35:09) - Winner’s Curse and Publication Bias (39:37) - Reproducibility Crisis (45:00) - Adversarial Collaboration (49:58) - Meta-Analysis and Pre-Registration (56:20) - Adversarial Discussion Sections and Updates (01:03:52) - Latest Red Study (01:07:23) - Wrap-Up

Can vitamin D really boost your athletic performance while slashing cancer risks? The hosts delve into claims of this miracle vitamin, discussing studies that tease out the truth. They tackle the challenges of observational studies and ecological fallacies, revealing how misleading correlations can be. Even promising trials, like VITAL, show no major benefits after rigorous testing. Their journey underscores that while vitamin D is essential for bones, more doesn't always mean better health, urging caution in supplementation.

Is America really facing an epidemic of vitamin D deficiency? While this claim is widely believed, the story behind it is packed with twists, turns, and some pesky statistical cockroaches. In this episode, we’ll dive into a study on Hawaiian surfers, expose how shifting goalposts can create an epidemic, tackle dueling medical guidelines, and flex our statistical sleuthing skills. By the end, you might wonder if the real deficiency lies in the data.Statistical topicsdichotomizationnormal distribution standard deviationresearcher biasesconflicts of intereststatistical sleuthingMethodologic morals“Arbitrary thresholds make for arbitrary diseases.”“Statistical errors are like cockroaches: Where there’s one, there’s many.”Note that all blood vitamin D levels discussed in the podcast are 25-hydroxyvitamin D levels given in units of ng/ml. To convert from ng/ml to nmol/L, use the formula: nmol/L=2.5*ng/ml. For example, a vitamin D level of 30 ng/mL corresponds to 75 nmol/L.CitationsDr. Rhonda Patrick: Micronutrients for Health & Longevity. Huberman Lab Podcast. May 1, 2022Noh CK, Lee MJ, Kim BK, et al. A Case of Nutritional Osteomalacia in Young Adult Male. J Bone Metab. 2013; 20:51-55.Binkley N, Novotny R, Krueger D, et al. Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab. 2007;92:2130-5. Malabanan A, Veronikis IE, Holick MF. Redefining Vitamin D Insufficiency. Lancet. 1998;351:805-6. Dawson-Hughes B, Heaney RP, Holick MF, et al. Estimates of optimal vitamin D status. Osteoporos Int. 2005;16:713-6. Holick MF. Vitamin D deficiency. N Engl J Med. 2007;357:266-81. Cui A, Xiao P, Ma Y, et al. Prevalence, trend, and predictor analyses of vitamin D deficiency in the US population, 2001-2018. Front Nutr. 2022;9:965376. Ross AC, Manson JE, Abrams SA, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: what clinicians need to know. J Clin Endocrinol Metab. 2011;96:53-8. Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, Treatment, and Prevention of Vitamin D Deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011;96:1911-30. Manson JE, Brannon PM, Rosen CJ, et al. Vitamin D deficiency-is there really a pandemic. N Engl J Med. 2016;375:1817-20. Conti G, Chirico V, Lacquaniti A, et al. Vitamin D intoxication in two brothers: be careful with dietary supplements. J Pediatr Endocrinol Metab. 2014;27:763-7.Holick, Michael, et al. The UV Advantage. Ibooks, 2004.Holick, Michael F. The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problems. Penguin Publishing Group, 2011.Szabo, Liz. Vitamin D, the Sunshine Supplement, Has Shadowy Money Behind It. The New York Times. August 18, 2018.Lee JM, Smith JR, Philipp BL, Chen TC, Mathieu J, Holick MF. Vitamin D deficiency in a healthy group of mothers and newborn infants. Clin Pediatr. 2007;46:42-4. Holick MF. Vitamin D deficiency: what a pain it is. Mayo Clin Proc. 2003;78:1457-9.Passeri G, Pini G, Troiano L, et al. Low Vitamin D Status, High Bone Turnover, and Bone Fractures in Centenarians. J Clin Endocrinol Metab. 2003;88:5109-15. Armstrong, David. The Child Abuse Contrarian. ProPublica. September 16, 2018.Irwig MS, Kyinn M, Shefa MC. Financial Conflicts of Interest Among Authors of Endocrine Society Clinical Practice Guidelines. J Clin Endocrinol Metab. 2018;103:4333-38. Demay MB, Pittas AG, Bikle DD, et al. Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2024;109:1907-47.McCartney CR, McDonnell ME, Corrigan MD, et al. Vitamin D Insufficiency and Epistemic Humility: An Endocrine Society Guideline Communication. J Clin Endocrinol Metab. 2024; 109:1948–54.See our detailed notes hereKristin and Regina’s online coursesDemystifying Data: A Modern Approach to Statistical Understanding Clinical Trials: Design, Strategy, and AnalysisMedical Statistics Certificate Program Writing in the SciencesEpidemiology and Clinical Research Graduate Certificate ProgramPrograms that we teach in:Epidemiology and Clinical Research Graduate Certificate Program Find us on:Kristin -  LinkedIn & Twitter/XRegina - LinkedIn & ReginaNuzzo.comChapters:(00:00) - Introduction (02:55) - Sources of Vitamin D (05:43) - What is Vitamin D & Why Do We Need It? (07:07) - Vitamin D Deficiency & Rickets (10:03) - Defining Vitamin D Deficiency – Changing the Goalposts ...

Sweaty t-shirt dating parties, sex pheromone dating sites, choosing your dating partner by sniffing them up — wacko fringe fads or evidence-based mating strategies? And what does your armpit stain have to do with your kids’ immune systems, or hormonal contraceptive pills, or divorce rates? In this episode of Normal Curves, Kristin and Regina reach back into the 1990s and revisit the scientific paper that started it all: The Sweaty T-Shirt Study. They bring a sharp eye and open mind, critically examining the study and following the line of research to today. Along the way, they encounter interesting statistical topics—including correlated observations, within-person study design, and bar-chart blasphemy—with a short, surprising detour into Neanderthal sex. Statistical topicsCorrelated observationsWithin-person study designBar charts Data and methodological transparencyCherry-pickingMeta-analysisMultiple testingPost-hoc analysesMethodological morals“Repeat after me: Bar charts are not for numerical data.”“Those who ignore dependencies in their data are destined for flawed conclusions.”ReferencesNuzzo, R. Ah, Love at first whiff. Los Angeles Times. May 19, 2008.Papamarko, S. Pheromone parties attempt to match singles by scent. Yahoo!life. April 12, 2012.Sainani, K. Stone Age Gene Swap. Stanford Magazine. November/December 2011.Aldhous, P. Darling, You Smell Wonderfully Different. New Scientist. 6 May 1995.Wedekind C, Seebeck T, Bettens F, Paepke AJ. MHC-dependent mate preferences in humans. Proc Biol Sci. 1995; 260(1359):245-249. doi:10.1098/rspb.1995.0087Hedrick P, Loeschcke V. MHC and mate selection in humans?. Trends Ecol Evol. 1996;11(1):24. doi:10.1016/0169-5347(96)80237-0Wedekind C, Seebeck T. Reply from C. Wedekind and T. Seebeck. Trends Ecol Evol. 1996;11(1):24-25. doi:10.1016/0169-5347(96)81061-5Wedekind C, Füri S. Body odour preferences in men and women: do they aim for specific MHC combinations or simply heterozygosity?. Proc Biol Sci. 1997;264(1387):1471-1479. doi:10.1098/rspb.1997.0204Havlíček J, Winternitz J, Roberts SC. Major histocompatibility complex-associated odour preferences and human mate choice: near and far horizons. Philos Trans R Soc Lond B Biol Sci. 2020;375(1800):20190260. doi:10.1098/rstb.2019.0260Kristin and Regina’s online courses: Demystifying Data: A Modern Approach to Statistical Understanding  Clinical Trials: Design, Strategy, and Analysis Medical Statistics Certificate Program  Writing in the Sciences Epidemiology and Clinical Research Graduate Certificate Program Programs that we teach in:Epidemiology and Clinical Research Graduate Certificate Program Find us on:Kristin -  LinkedIn & Twitter/XRegina - LinkedIn & ReginaNuzzo.com(00:00) - Introduction (02:27) - Pheromone Dating Parties (06:57) - Pheromone Dating Sites and Genetic Matching (10:47) - The Science of HLA Genes and Mate Selection (18:08) - Breaking Down the Original Sweaty T-Shirt Study (24:05) - Study Design Flaws and Data Transparency Issues (28:28) - Statistical Flaws: Correlated Observations Explained (36:19) - Analyzing the Study's Questionable Results (39:15) - The Pill's Influence on Scent Preferences (42:23) - Overstated Conclusions and Wandering Discussions (47:50) - Media Reactions and the Study’s Public Impact (54:03) - Other Studies and their results (56:42) - Conclusion

Join a vibrant discussion where science meets fun! Discover how two professors forged a lasting friendship during their PhDs. They dive into the art of evaluating scientific studies and the importance of clear communication. Reflect on personal health journeys and how they faced biases in research. Hear a heartfelt story about cochlear implants and the transformative power of clinical trials. Plus, get a glimpse into their engaging teaching styles and the provocative topics that shape their lively conversations.