6 Needs context
Adult humans produce approximately 700 new hippocampal stem cells each day.
"And in one study I read, you actually make 700 new stem cells, hippocampal stem cells, every day." (said at 0:07:00)
The speaker is referencing a landmark 2013 study by Spalding and colleagues (Cell), which used carbon-14 dating from nuclear bomb testing to estimate that approximately 700 new neurons (not stem cells) are added in each hippocampus per day in adult humans, corresponding to an annual turnover rate of 1.75% within the renewing neuronal population. However, this estimate refers to newly generated neurons rather than stem cells, and the broader scientific community remains divided regarding the extent of adult human hippocampal neurogenesis, with subsequent postmortem studies (e.g., Sorrells et al., Nature 2018) finding that neurogenesis drops to undetectable or extremely rare levels in adulthood.
- supports: Dynamics of hippocampal neurogenesis in adult humans. (Cell 2013) · cited 1831x in the literature
"In adult humans, 700 new neurons are added in each hippocampus per day, corresponding to an annual turnover of 1.75% of the neurons within the renewing fraction, with a modest decline during aging." (abstract, results, passage verified)
pubmedfull study (doi) - context: Human hippocampal neurogenesis drops sharply in children to undetectable levels in adults. (Nature 2018) · cited 1416x in the literature
"We conclude that recruitment of young neurons to the primate hippocampus decreases rapidly during the first years of life, and that neurogenesis in the dentate gyrus does not continue, or is extremely rare, in adult humans." (abstract, results, passage verified)
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A study from Harvard found that 40% of 40-year-olds and 70% of 70-year-olds have erectile dysfunction.
"And I read one study from Harvard that said 40% of 40-year-olds have erectile dysfunction and 70% of 70-year-olds." (said at 0:09:35)
This commonly cited rule of thumb originates from the Massachusetts Male Aging Study (MMAS), a landmark population-based study conducted near Boston in men aged 40 to 70. The study found that total erectile dysfunction (combining minimal, moderate, and complete impotence) was present in approximately 40% of men at age 40 and approximately 70% of men at age 70 (overall combined prevalence of 52%). However, most cases in younger cohorts represent mild or minimal dysfunction; severe or complete erectile dysfunction occurred in only about 5% of 40-year-olds and 15% of 70-year-olds.
- context: Impotence and its medical and psychosocial correlates: results of the Massachusetts Male A… (The Journal of urology 1994) · cited 5122x in the literature
"The Massachusetts Male Aging Study was a community based, random sample observational survey of noninstitutionalized men 40 to 70 years old conducted from 1987 to 1989 in cities and towns near Boston, Massachusetts. Blood samples, physiological measures, socio-demographic variables, psychological indexes, and information on health status, medications, smoking and lifestyle were collected by trained interviewers in the subject's home. A self-administered sexual activity questionnaire was used to characterize erectile potency. The combined prevalence of minimal, moderate and complete impotence was 52%. The prevalence of complete impotence tripled from 5 to 15% between subject ages 40 and 70 years." (abstract, results, passage verified)
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Ninety-four percent of traumatic brain injuries affect the frontal lobes.
"so of traumatic brain injuries, 94% of them affect the frontal lobes" (said at 0:32:48)
The speaker claims that 94% of traumatic brain injuries (TBIs) affect the frontal lobes. This statistic originates from a systematic review evaluating the clinical utility of single-photon emission computed tomography (SPECT) in TBI (Raji et al., 2014). The systematic review found that across cross-sectional brain SPECT imaging studies of TBI patients, the frontal lobes were the most common region showing neuroimaging abnormalities (94% of cross-sectional studies reported frontal lobe abnormalities, and 77% reported temporal lobe abnormalities).
However, stating that 94% of all traumatic brain injuries affect the frontal lobes misrepresents what the statistic actually measures. The 94% figure refers to the proportion of cross-sectional SPECT studies in a systematic review that identified frontal lobe perfusion abnormalities among evaluated TBI patients, not a epidemiological population measure that 94% of all clinical TBI incidents involve frontal lobe injury.
Undergoing coronary artery bypass surgery increases the risk of cognitive impairment and Alzheimer's disease.
"and for example, if you have coronary artery bypass surgery, that increases your risk of having cognitive impairment and Alzheimer's disease." (said at 0:35:33)
The claim that coronary artery bypass graft (CABG) surgery increases the risk of cognitive impairment and Alzheimer's disease requires important qualification. Postoperative cognitive decline and short-term cognitive impairment are common following CABG surgery, with meta-analyses reporting acute cognitive impairment in roughly 35% to 43% of patients post-CABG. However, evidence on whether CABG independently increases the long-term risk of Alzheimer's disease compared to non-surgical cardiovascular disease remains mixed. While some population studies show an elevated hazard ratio for dementia and Alzheimer's disease in patients with a history of CABG, large national registry studies show no overall increase in all-cause dementia risk compared to matched controls, and controlled longitudinal studies suggest cognitive trajectories in these patients are primarily driven by underlying vascular disease and cardiovascular risk factors rather than the surgery itself.
- context: Neurocognitive outcomes 3 years after coronary artery bypass graft surgery: a controlled s… (The Annals of thoracic surgery 2007) · cited 81x in the literature
"We found a mild but nonsignificant trend toward late postoperative cognitive decline for all study groups with coronary artery disease, but no significant differences in the degree of late postoperative cognitive decline after on-pump compared with off-pump surgery. These findings suggest that previously reported late decline after bypass surgery is not specific to use of cardiopulmonary bypass." (abstract, conclusions, passage verified)
pubmedfull study (doi) - partial: Coronary Artery Bypass Graft Surgery and Dementia Risk in the Cardiovascular Health Study. (Alzheimer disease and associated disorders 2017) · cited 30x in the literature
"In the CHS, the hazard ratio (HR) for all-cause dementia was 1.93 [95% confidence interval (CI), 1.36-2.74] for those with CABG history compared with those with no CABG history after adjustment for potential confounders. Similar HRs were observed for AD (HR=1.71; 95% CI, 0.98-2.98)..." (abstract, results, passage verified)
pubmedfull study (doi) - supports: Cognitive outcomes following coronary artery bypass grafting: A systematic review and meta… (International journal of cardiology 2019) · cited 172x in the literature
"Pre-surgical cognitive impairment was seen in 19% of patients. Post-operatively, cognitive impairment was seen in around 43% of patients acutely; this resolved to 19% at 4-6 months and then increased to 25% of patients between 6-months to 1-year post-operatively. In the long term, between 1 and 5-years post-operatively, cognitive impairment increased and was seen in nearly 40% of patients." (abstract, results, passage verified)
pubmedfull study (doi) - contradicts: The risk of dementia after coronary artery bypass grafting in relation to age and sex. (Alzheimer's & dementia : the journal of the Alzheimer's Association 2021) · cited 17x in the literature
"There was no difference in the risk for all-cause dementia between CABG patients and control subjects (aHR 0.98 [95% confidence interval 0.95 to 1.02])." (abstract, results, passage verified)
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A long-term longevity study found that conscientiousness was the primary personality predictor of longevity, while highly cheerful or unworried individuals died earlier from accidents or preventable illnesses.
"So you might know the longevity study, the one from Harvard where they look at people over 90 years, the number one predictor of longevity was not happiness or a lack of worry—"Don't worry, be happy" people died the earliest from accidents or preventable illnesses, so I always wanted to be one of those people, I'm not—that the number one predictor was conscientiousness." (said at 0:39:16)
The speaker accurately describes the core findings of a landmark multi-decade lifespan study, although the research referenced is the Terman Life Cycle Study (analyzed extensively by Howard S. Friedman and colleagues, often called The Longevity Project out of Stanford/UC Riverside), rather than the Harvard Study of Adult Development. In analyses following participants from childhood across seven to eight decades, childhood conscientiousness emerged as the strongest personality predictor of longevity, whereas cheerfulness and high optimism were unexpectedly associated with reduced longevity, partly due to increased engagement in health-risk behaviors and preventable mortality. Meta-analyses have further confirmed the positive relationship between conscientiousness and survival.
- supports: Do conscientious individuals live longer? A quantitative review. (Health psychology : official journal of the Division of Health Psychology, American Psychological Association 2008) · cited 462x in the literature
"Higher levels of conscientiousness were significantly and positively related to longevity (r = .11, 95% confidence interval = .05-.17)." (abstract, conclusions, passage verified)
pubmedfull study (doi) - supports: Sociodemographic and psychosocial factors in childhood as predictors of adult mortality. (American journal of public health 1995) · cited 182x in the literature
"Three dimensions of childhood personality--conscientiousness, lack of cheerfulness, and permanency of mood (males only)--predicted increased longevity." (abstract, results, passage verified)
pubmedfull study (doi) - supports: Does childhood personality predict longevity? (Journal of personality and social psychology 1993) · cited 423x in the literature
"Conscientiousness in childhood was clearly related to survival in middle to old age... Contrary to expectation, cheerfulness (optimism and sense of humor) was inversely related to longevity, suggesting a possible need for reconceptualization of its health relevance." (abstract, results)
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Approximately 6.5 million American children have an ADHD diagnosis, with about two-thirds receiving medication.
"the statistic is that about 6.5 million American children carry a diagnosis of ADHD and about two-thirds of them are medicated, most of whom are medicated with stimulants and basically amphetamines." (said at 0:43:43)
The speaker's statement combines statistics from different survey cycles of the U.S. National Survey of Children's Health (NSCH). According to 2022 NSCH data published by CDC researchers, an estimated 6.5 million U.S. children aged 3–17 years currently have an ADHD diagnosis (10.5%). However, in that same 2022 survey, 53.6% (approximately half) of children with current ADHD were receiving medication. The "about two-thirds" figure corresponds to earlier NSCH data cycles, such as 2016 (where 62.0% were taking medication) and 2011 (where 69% were taking medication).
- context: Trends in the parent-report of health care provider-diagnosed and medicated attention-defi… (Journal of the American Academy of Child and Adolescent Psychiatry 2014) · cited 1277x in the literature
"In 2011, 11% of children/adolescents aged 4 to 17 years had ever received an ADHD diagnosis (6.4 million children)... 69% of children with current ADHD were taking medication for ADHD" (abstract, results)
pubmedfull study (doi) - context: Prevalence of Parent-Reported ADHD Diagnosis and Associated Treatment Among U.S. Children … (Journal of clinical child and adolescent psychology : the official journal for the Society of Clinical Child and Adolescent Psychology, American Psychological Association, Division 53 2018) · cited 1196x in the literature
"In 2016, an estimated 6.1 million U.S. children 2-17 years of age (9.4%) had ever received an ADHD diagnosis. Of these, 5.4 million currently had ADHD... Of children with current ADHD, almost two thirds (62.0%) were taking medication" (abstract, results)
pubmedfull study (doi) - supports: ADHD Prevalence Among U.S. Children and Adolescents in 2022: Diagnosis, Severity, Co-Occur… (Journal of clinical child and adolescent psychology : the official journal for the Society of Clinical Child and Adolescent Psychology, American Psychological Association, Division 53 2024) · cited 296x in the literature
"Approximately 1 in 9 U.S. children have ever received an ADHD diagnosis (11.4%, 7.1 million children) and 10.5% (6.5 million) had current ADHD. Among children with current ADHD, 58.1% had moderate or severe ADHD, 77.9% had at least one co-occurring disorder, approximately half of children with current ADHD (53.6%) received ADHD medication" (abstract, results, passage verified)
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Unverified means no publication matching the claim was located; it does not prove the claim false. Spotted an error? See the corrections policy - disputes from the people quoted are prioritized.