Age Differences Research Articles

1 km of living area: age differences in the association between neighborhood environment perception and self-rated health among Chinese people

ObjectivesThis study aimed to explore the age differences in the relationship between neighborhood environment perception and self-rated health among Chinese people.Study designThis is cross-sectional study.MethodsThe participants were 2,631 residents aged 18 and above from 2021 Chinese General Social Survey (CGSS). Self-rated health was reported by residents. Neighborhood environment was measured by respondents’ subjective perception of 1 km living area. Ordered logit regression models were used to examine the relationship between neighborhood environment perception and self-rated health.ResultsIn summary, 42.08% were classified as young adults, and 57.92% were classified as middle-aged and older adults. Young adults with higher perception of neighborhood social environment were more likely to perceive good health. Neighborhood built environment was significantly associated with self-rated health among middle-aged and older adults.ConclusionThe neighborhood environment is an important predictor of the health of its residents. Neighborhood environmental modifications should be tailored to meet the needs of different age groups, promoting health equity.

The Prader-Willi syndrome Profile: validation of a new measure of behavioral and emotional problems in Prader-Willi syndrome.

Prader-Willi syndrome (PWS) is a rare, neurodevelopmental disorder caused by the lack of expression of paternally imprinted genes on chromosome 15q11-13. PWS features a complex behavioral phenotype, including hyperphagia, anxiety, compulsivity, rigidity, repetitive speech, temper outbursts, aggressivity, and skin-picking. Questionnaires exist for measuring hyperphagia, but not for the aggregation of other problems that are distinctive to PWS. A PWS-specific tool is needed for phenotypic research, and to help evaluate treatment efficacy in future clinical trials aimed at attenuating PWS's hyperphagia and related problems. In this 4-phase study, we leveraged our expertise in PWS with feedback from families and specialists to validate the PWS Profile, a novel, informant-based measure of behavioral and emotional problems in this syndrome. The authors developed a bank of 73 items that tapped both common and less frequent but clinically significant problems in PWS (Phase 1). An iterative feedback process with families and stakeholders was used to ensure content and construct validity (Phase 2). After adding, omitting, or revising items, in Phase 3, we pilot tested the measure in 112 participants. Results were reviewed by an international team of PWS specialists and revised again (Phase 3). The final, 57-item Profile was then administered to 761 participants (Phase 4). Principal component factor analyses (n = 873) revealed eight conceptually meaningful factors, accounting for 60.52% of test variance, and were readily interpretated as: Rigidity, Insistence; Aggressive Behaviors; Repetitive Questioning, Speech; Compulsive Behaviors; Depression, Anxiety; Hoarding; Negative Distorted Thinking; and Magical Distorted Thinking. Factors were internally consistent and showed good test-retest reliability and convergent validity with existent measures of behavioral problems. Profile factors were not related to IQ, BMI, or parental SES. Three Profile factors differed across PWS genetic subtypes. Age and gender differences were found in only one Profile factor, Hoarding. The PWS Profile is a valid, psychometrically-sound questionnaire that already has shown responsivity to treatment in a previous clinical trial. The Profile can extend the reach of future clinical trials by evaluating the impact of novel agents not only on hyperphagia, but also on the emotional and behavioral problems that characterize PWS.

Insights into the diagnosis and management of sarcoid uveitis: A review.

Sarcoidosis is a leading cause of non-infectious uveitis that commonly affects middle-aged individuals and has a female preponderance. The disease demonstrates age, sex and ethnic differences in clinical manifestations. A diagnosis of sarcoidosis is made based on a compatible clinical presentation, supporting investigations and histologic evidence of non-caseating granulomas, although biopsy is not always possible. Multimodal imaging with widefield fundus photography, optical coherence tomography and angiography can help in the diagnosis of sarcoid uveitis and in the monitoring of treatment response. Corticosteroid remains the mainstay of treatment; chronic inflammation requires steroid-sparing immunosuppression. Features on multimodal imaging such as vascular leakage may provide prognostic indicators of outcome. Female gender, prolonged and severe uveitis, and posterior involving uveitis are associated with poorer visual outcomes.

Microbial profile in bile from pancreatic and extra-pancreatic biliary tract cancer.

Dysbiotic biliary bacterial profile is reported in cancer patients and is associated with survival and comorbidities, raising the question of its effect on the influence of anticancer drugs and, recently, the suggestion of perichemotherapy antibiotics in pancreatic cancer patients colonized by the Escherichia coli and Klebsiella pneumoniae. In this study, we investigated the microbial communities that colonize tumours and which bacteria could aid in diagnosing pancreatic and biliary cancer and managing bile-colonized patients. A retrospective study on positive bile cultures of 145 Italian patients who underwent cholangiopancreatography with PC and EPC cancer hospitalized from January 2006 to December 2020 in a QA-certified academic surgical unit were investigated for aerobic/facultative-anaerobic bacteria and fungal organisms. We found that among Gram-negative bacteria, Escherichia coli and Pseudomonas spp were the most frequent in the EPC group, while Escherichia coli, Klebsiella spp, and Pseudomonas spp were the most frequent in the PC group. Enterococcus spp was the most frequent Gram-positive bacteria in both groups. Comparing the EPC and PC, we found a significant presence of patients with greater age in the PC compared to the EPC group. Regarding Candida spp, we found no significant but greater rate in the PC group compared to the EPC group (11.7% vs 1.96%). We found that Alcaligenes faecalis was the most frequent bacteria in EPC than the PC group, among Gram-negative bacterial species. Age differences in gut microbiota composition may affect biliary habitats in our cancer population, especially in patients with pancreatic cancer. Alcaligenes faecalis isolated in the culture of bile samples could represent potential microbial markers for a restricted follow-up to early diagnosis of extra-pancreatic cancer. Finally, the prevalence of Candida spp in pancreatic cancer seems to trigger new aspects about debate about the role of fungal microbiota into their relationship with pancreatic cancer.

Growing Up in a Polarized Party System: Ideological Divergence and Partisan Sorting Across Generations

AbstractAmerican political elites have increasingly polarized over the past decades, which has inspired much research into mass polarization. We study whether there is a generational component to mass polarization by disentangling period, age, and cohort differences while distinguishing two forms of mass polarization: partisan sorting and ideological divergence. Drawing from General Social Survey and American National Election Studies data, we find that partisan sorting has increased across long-standing and emerging issues, while ideological divergence has not. Contrary to expectations, over-time increases in sorting are clearly driven by changes within generations rather than by generational replacement. On several issues, newer generations turn out to be less sorted than those they replace. This tentatively suggests that, partially as a consequence of demographic changes, generational replacement will gradually lead to less polarization in American public opinion as it converges toward more liberal positions.

Neuroinflammation and acquired traumatic CNS injury: a mini review.

Acquired traumatic central nervous system (CNS) injuries, including traumatic brain injury (TBI) and spinal cord injury (SCI), are devastating conditions with limited treatment options. Neuroinflammation plays a pivotal role in secondary damage, making it a prime target for therapeutic intervention. Emerging therapeutic strategies are designed to modulate the inflammatory response, ultimately promoting neuroprotection and neuroregeneration. The use of anti-inflammatory agents has yielded limited support in improving outcomes in patients, creating a critical need to re-envision novel approaches to both quell deleterious inflammatory processes and upend the progressive cycle of neurotoxic inflammation. This demands a comprehensive exploration of individual, age, and sex differences, including the use of advanced imaging techniques, multi-omic profiling, and the expansion of translational studies from rodents to humans. Moreover, a holistic approach that combines pharmacological intervention with multidisciplinary neurorehabilitation is crucial and must include both acute and long-term care for the physical, cognitive, and emotional aspects of recovery. Ongoing research into neuroinflammatory biomarkers could revolutionize our ability to predict, diagnose, and monitor the inflammatory response in real time, allowing for timely adjustments in treatment regimens and facilitating a more precise evaluation of therapeutic efficacy. The management of neuroinflammation in acquired traumatic CNS injuries necessitates a paradigm shift in our approach that includes combining multiple therapeutic modalities and fostering a more comprehensive understanding of the intricate neuroinflammatory processes at play.

Month of Birth and Cognitive Effort: A Laboratory Study of the Relative Age Effect among Fifth Graders

Abstract All around the world, school-entry cohorts are organized on an annual calendar so that the age of students in the same cohort differs by up to one year. It is a well-established finding that this age gap entails a consequential (dis)advantage for academic performance referred to as the relative age effect (RAE). This study contributes to a recent strand of research that has turned to investigate the RAE on non-academic outcomes such as personality traits. An experimental setup is used to estimate the causal effect of monthly age on cognitive effort in a sample of 798 fifth-grade students enrolled in the Spanish educational system, characterized by strict enrolment rules. Participants performed three different real-effort tasks under three different incentive conditions: no rewards; material rewards; and material and status rewards. We observe that older students outwork their youngest peers by two-fifths of a standard deviation, but only when material rewards for performance are in place. Despite the previously reported higher taste for competition among the older students within a school-entry cohort, we do not find that the RAE on cognitive effort increases after inducing competition for peer recognition. Finally, the study also provides suggestive evidence of a larger RAE among boys and students from lower social strata. Implications for sociological research on educational inequality are discussed. To conclude, we outline policy recommendations such as implementing evaluation tools that nudge teachers toward being mindful of relative age differences.

A bifactor representation of the Center for Epidemiological Studies Depression Scale for children: gender and age invariance and implications for adolescents’ social and academic adjustment

BackgroundThe Center for Epidemiological Studies Depression Scale for Children (CES-DC) is a widely used scale for screening depressive symptoms in children and adolescents. This study aims to uncover the optimal factor structure of the DES-DC and presents an alternate conceptualization of adolescent depression by estimating bifactor models and several competing models using a sample of Chinese adolescents.MethodsThe participants were 533 adolescents (49.7% boys, 49.7% girls, 3 participants did not report) between 12 and 18 years of age attending public secondary schools in the middle part of mainland China. Data were collected in classrooms using a questionnaire survey. A structural equation modeling approach was used to estimate and compare a series of competing models for the DES-DC.ResultsA Bifactor exploratory structural equation model (Bi-ESEM) with the best model fit was retained for representing the current data. Tests of measurement invariance demonstrated strict measurement equivalence across gender and age. No gender and age differences have been found in the general depression factor. Findings provided evidence for the composite reliability and construct validity of DES-DC. Depressive symptoms positively related to the Big Five trait neuroticism, negative emotions, loneliness, social anxious behaviors, and disruptive behaviors during school and negatively related to agreeableness, conscientiousness, extraversion, physical health status, school connectedness, and academic self-efficacy.ConclusionsThis study provides support for the one general factor construct of the CES-DC and the continuum concept structure of adolescent depression. Moreover, this research offers empirical evidence for comparing depression symptoms among adolescent populations with diverse genders and age groups. Additionally, the findings replicate and expand upon the implications of depressive symptoms on adolescents’ traits, well-being, social-relational adjustment, and academic adaptation.

Relationship Between Habitual Use and Degree of Emotion Regulation: Age Differences in Cognitive Reappraisal and Expressive Suppression.

The present study examined age differences in and the relationship between two indices of cognitive reappraisal and expressive suppression: the degree of emotion regulation and the habitual use of emotion-regulation strategies. In total, 101 younger and 99 older participants were included in this study. The degree of emotion regulation was measured using an experimental task in which participants were presented with negative or positive pictures and required to regulate their emotions. Habitual use of emotion regulation strategies was measured using an emotion regulation questionnaire. The results showed that younger adults regulated their emotions to a greater extent than older adults in both reappraisal and suppression. Younger adults were more likely to use reappraisal than were older adults, although there were no age differences in the use of suppression. No significant correlations were found between the degree of emotion regulation and the habitual use of emotion regulation strategies. These results suggest that age differences in emotion regulation depend on the regulation strategy and that the degree of emotion regulation and habitual use of emotion regulation strategies are independent and quite different indicators in nature.

Age difference of patients with and without invasive aspergillosis: a systematic review and meta-analysis.

Invasive Aspergillosis (IA) is a life-threatening fungal disease with significant mortality rates. Timely diagnosis and treatment greatly enhance patient outcomes. This study aimed to explore the association between patient age and the development of IA, as well as the potential implications for risk stratification strategies. We searched National Center for Biotechnology Information (NCBI) databases for publications until October 2023 containing age characteristics of patients with and without IA. A random-effects model with the application of inverse-variance weighting was used to pool reported estimates from each study, and meta-regression and subgroup analyses were utilized to assess sources of heterogeneity. A systematic review was conducted, resulting in the inclusion of 55 retrospective observational studies with a total of 13,983 patients. Meta-analysis revealed that, on average, patients with IA were approximately two and a half years older (95% Confidence Interval [CI] 1.84-3.31 years; I2 = 26.1%) than those without the disease (p < 0.0001). No significant moderators could explain the observed heterogeneity in age difference. However, subgroup analysis revealed that age differences were more pronounced within particular patient groups compared to others. For example, patients with and without IA who had primary severe lung infections exhibited a greater difference in mean age than other patient cohorts. Further research, such as individual patient data meta-analysis, is necessary to better understand the potential relationship between increasing age and the likelihood of IA. Improved risk stratification strategies based on patient age could potentially enhance the early detection and treatment of IA, ultimately improving patient outcomes.

Exposure of Neighborhood Racial and Socio-Economic Composition in Activity Space: A New Approach Adjusting for Residential Conditions

Abstract A longstanding urban sociological literature emphasizes the geographic isolation of city dwellers in residence and everyday routines, expecting exposures to neighborhood racial and socio-economic structure driven principally by city-wide segregation and the role of proximity and homophily in mobility. The compelled mobility approach emphasizes the uneven distribution of organizational and institutional resources across urban space, expecting residents of poor Black-segregated neighborhoods to exhibit non-trivial levels of everyday exposure to White, non-poor areas for resource seeking. We use two sets of location data in the hypersegregated Chicago metro to examine these two approaches: Global Positioning System (GPS) location tracking on a sample of older adults from the Chicago Health and Activity Space in Real-Time (CHART) study and travel diaries on a sample of younger adults by the Chicago Metropolitan Agency for Planning (CMAP). We introduce a novel and flexible individual-level method for assessing activity space exposures that accounts for the spatially proximate environment around home. Analyses reveal that activity space contexts mimic the racial/ethnic and socio-economic landscape of respondents’ broad residential environment. However, after residential-based adjustment, Black younger (CMAP) adults from poor Black neighborhoods are disproportionately exposed to Whiter, less Black but less non-poor neighborhoods. Older (CHART) adult activity spaces align more closely with their residential areas; however, activity spaces of poor-Black-neighborhood-residing CHART Blacks are systematically poorer and, less consistently, more Black and less White after local area adjustment. Implications for understanding contextual exposures on well-being and the potential for age or cohort differences in isolation are discussed.

Naturalistic assessments in virtual reality and in real life help resolve the age-prospective memory paradox

ABSTRACT Cognitive aging researchers have long reported “paradoxical” age differences in prospective memory (PM), with age deficits in laboratory settings and age benefits (or no deficits) in real-world settings. We propose a theoretical account that explains this “age-PM-paradox” as a consequence of both methodological factors and developmental changes in cognitive abilities and personality traits. To test this account, young and older adults performed a series of naturalistic PM tasks in the lab and real world. Age-related PM deficits were observed in both lab-based tasks where demands were implemented using virtual reality and in-person role-playing. In contrast, older adults performed equal to or better than young adults on both real-world tasks, where demands were implemented in participants’ daily lives. Consistent with our proposed account, an index of these “paradoxical” effects was partially predicted by age-related differences in working memory, vigilance, agreeableness, and neuroticism, whose predictive utility varied across task settings.

The Comparative Effect of Occupational and Musical Enrichment on Fecal Glucocorticoid Metabolite Levels in a Captive Colony of Stumptail Macaques (Macaca arctoides).

Environmental enrichment improves captive animal welfare by reducing stress-related behaviors. Previous studies in a captive colony of stumptail macaques (Macaca arctoides) reported a reduction of aggression, coprophilia, and stereotypic behaviors after an occupational enrichment program; however, the effect on stress hormones such as glucocorticoids has not been investigated yet. The goal of this study was to compare the effect of sex, age, and social rank on changes in fecal glucocorticoid metabolites (fGCM) after applying two kinds of enrichments (occupational vs. musical) in a captive colony of stumptail macaques. We collected 234 fecal samples from 25 stumptail macaques under the following conditions: (1) basal (no enrichment), (2) three weeks of occupational enrichment, and (3) three weeks of relaxing/classical music. The Generalized Estimated Equation Model showed an increase in fGCM levels after the occupational enrichment only in adult subjects (p = 0.003 compared to basal). The fGCM levels reached by the adults after the occupational enrichment was higher than that of juveniles (p = 0.002) and subadults (p = 0.02). Occupational and musical enrichment decreased fGCM levels only in middle-ranking individuals (p < 0.001 and p = 0.013, respectively). No sex differences were found. In conclusion, there were age and rank differences in individuals' physiological reactivity to the effects of environmental enrichment which need to be considered when planning enrichment programs.

Health Services Utilization and Specialist Care in Pediatric Inflammatory Bowel Disease: A Multiprovince Population-Based Cohort Study.

Patterns of health services utilization among children with inflammatory bowel disease (IBD) are important to understand as the number of children with IBD continues to increase. We compared health services utilization and surgery among children diagnosed <10 years of age (Paris classification: A1a) and between 10 and <16 years of age (A1b). Incident cases of IBD diagnosed <16 years of age were identified using validated algorithms from deterministically linked health administrative data in 5 Canadian provinces (Alberta, Manitoba, Nova Scotia, Ontario, Quebec) to conduct a retrospective cohort study. We compared the frequency of IBD-specific outpatient visits, emergency department visits, and hospitalizations across age groups (A1a vs A1b [reference]) using negative binomial regression. The risk of surgery was compared across age groups using Cox proportional hazards models. Models were adjusted for sex, rural/urban residence location, and mean neighborhood income quintile. Province-specific estimates were pooled using random-effects meta-analysis. Among the 1165 (65.7% Crohn's) children with IBD included in our study, there were no age differences in the frequency of hospitalizations (rate ratio [RR], 0.88; 95% confidence interval [CI], 0.74-1.06) or outpatient visits (RR, 0.95; 95% CI, 0.78-1.16). A1a children had fewer emergency department visits (RR, 0.70; 95% CI, 0.50-0.97) and were less likely to require a Crohn's-related surgery (hazard ratio, 0.49; 95% CI, 0.26-0.92). The risk of colectomy was similar among children with ulcerative colitis in both age groups (hazard ratio, 0.71; 95% CI, 0.49-1.01). Patterns of health services utilization are generally similar when comparing children diagnosed across age groups.

Social Influencer or Celebrity Endorser, To Whom Do Multicultural Consumers Pay Attention in Instagram? Comparing Medium- and High-Involvement Products Across Ethnic Groups

This study investigates the influence of social media influencers and celebrity endorsements on attitudes and intentions to purchase high and medium-involvement products on Instagram. A multimethod research design was used, with a national sample of 799 Instagram users. Results show that celebrity endorsements are more impactful than social media influencers for High and medium-involvement products. However, social media influencers influence more males, but attitudes remain consistent across genders. Celebrity endorsements and influencers have the highest impact on Millennials. The study reveals that celebrities are more influential than celebrity endorsements for medium-involvement products. There are significant gender and age differences but no ethnic differences. Males are more influenced by celebrities and influencers on Instagram, but their attitude toward influencers remains consistent. Celebrity endorsement and influencers have the highest impact on Millennials, followed by Gen X, baby boomers, and Gen Z, with no significant difference between Gen Z and baby boomers.

The Effect of Background Noise, Bilingualism, Socioeconomic Status, and Cognitive Functioning on Primary School Children's Narrative Listening Comprehension.

This study focuses on 7- to 9-year-old children attending primary school in Swedish areas of low socioeconomic status, where most children's school language is their second language. The aim was to better understand what factors influence these children's narrative listening comprehension both in an ideal listening condition (in quiet) and for the primary school classroom, a typical listening condition (with multitalker babble noise). A total of 86 typically developing 7- to 9-year-olds performed a narrative listening comprehension test (Lyssna, Förstå och Minnas [LFM]; English translation: Listen, Comprehend, and Remember) in two listening conditions: quiet and multitalker babble noise. They also performed the crosslinguistic nonword repetition test and a digit span backwards (DSB) test. A predictive statistical model including these factors, the children's degree of school language exposure, parental education level, and age was derived. Listening condition had the strongest predictive value for LFM performance, followed by school language exposure and nonword repetition accuracy. Parental education level was also a significant predictor. There was a significant three-way interaction effect between listening condition, age, and DSB performance. Multitalker babble noise has a negative effect on children's narrative listening comprehension. The effect of multitalker babble noise could be explained by age differences in the ability to allocate working memory capacity during the narrative listening comprehension task, suggesting that younger children may be more vulnerable for missing information when listening in background noise than their older peers. https://doi.org/10.23641/asha.25209248.

Mental Telehealth Utilization Patterns Among High School Students from Racial and Ethnic Minority Backgrounds Affected by Violence and Substance Use.

Recent data show high school students from racial and ethnic minority (REM) backgrounds in the United States confront a twofold challenge, marked by the highest rates of firearm-related homicides since 1994 and increased youth substance use. The pandemic increased online and telehealth usage opportunities for at-risk REM youth. Therefore, this study investigated (1) the frequency and prevalence of co-occurring youth violence and substance use among REM adolescents, (2) racial/ethnic, age, and natal sex (as gender data was not collected) differences in patterns and trends in co-occurring youth violence and substance use among REM adolescents, and (3) the relationship between these syndemic issues and REM adolescent mental telehealth use during the pandemic. Data was sourced from a nationally representative sample of U.S. 9th-12th students (n = 3241) who completed the CDC's 2021 Adolescent and Behavioral Experiences Survey (ABES). Using univariate (frequency distribution), bivariate (Pearson's chi-squared test), and multivariate logistic regression models, we examined seven violence victimization outcomes, four violence perpetration outcomes, two family violence outcomes, and six substance use outcomes and their associations with telehealth use for mental health (dependent variable) among REM adolescents. This sample was primarily female (50.7%), Black or African American (48.3%), Hispanic or Latinx (20.6%), and identified as straight or heterosexual (69.5%). The study found significant sex-based differences in violence perpetration/victimization, substance use, and telehealth use for mental health. In general, mental telehealth use was significantly associated with substance use among REM adolescents (cigarette smoking, vaping, alcohol, marijuana, prescription meds, and illicit drug use) (p-value = .001). Mental telehealth use was also significantly associated with all peer and family violence outcomes (p < 0.001). Controlling for covariates, gun carrying was associated with 4.8 times higher odds of using mental telehealth. Students in a physical fight or carrying a weapon (gun, knife, or club) on school property had 2.45 times and 8.09 times the odds of utilizing mental telehealth. Bullied students were 2.5 times more likely to use mental telehealth (p-value < 0.05). Illicit drug use (cocaine, heroin, methamphetamines, and ecstasy) was associated with a higher likelihood of mental telehealth use (AOR = 1.3, p-value = .05). Our results suggest crucial insights for shaping violence and substance use prevention strategies, with implications for the future of online and telehealth behavioral services. Mental telehealth help-seeking emerges as a crucial avenue for supporting adolescents affected by violence and substance use, especially when they face obstacles to accessing traditional services. It can work in tandem with in-person services to address these challenges.

Younger and Older Adults' Health Lies to Close Others.

Lying is a common social behavior; however, there is limited research on lying about health and if this differs into later life. This study sought to explore age differences in the frequency of and motivations behind telling health-related lies and if lying differs within romantic and parent/child relationships. Younger (N = 158) and older adults (N = 149) reported how often they told general health-related lies, how often they lied about health to their romantic partner and parent or adult child, and why they told health lies. Compared with older adults, younger adults lied more frequently to conceal sickness and pain as well as to feign sickness. Younger adults also told more health lies to their parent than their romantic partner, but older adults lied to their adult child and partner at similar rates. Younger adults reported lying more about their health because they felt ashamed or embarrassed and they worried about what others would think of them compared with older adults. These results suggest that health-related honesty may increase in later life and that younger and older adults differ in why they tell health lies. Implications for psychological theory on lying about one's health and health interventions are discussed.

Edward F. Adolph Distinguished Lecture. Age and sex differences in the limits of human performance: fatigability and real-world data.

High-level athletic performances may be a proxy for the trajectory of optimal function of human biology with advanced aging and the differences between males and females. Males are faster, stronger, and more powerful than females and these physical attributes decline dramatically with advanced aging for both sexes. Experimental mechanistic studies determine the physiological mechanisms for these sex and age differences in human physical performance. The assumption however, that real-world performances solely reflect the biological and physiological differences between the sexes and with advanced aging, even among elite athletes, is not complete. This review presents evidence that an integrated approach encompassing analysis of real-world data and experimental mechanistic studies is necessary to determine the biological and sociocultural factors attributed to the limits of performance with aging and between males and females. First, experimental studies are presented that focus on the sex and age differences in performance fatigability that determine the physiological mechanisms of absolute and relative exercise performance. Second, analysis of current and historical real-world data including world records, and performances of elite, collegiate, and competitive age-group athletes are highlighted. These data illustrate that the upper limits of physical performance that have changed historically, and other factors such as sociocultural influences, explain the widening of the sex and age gaps in human performance observed in real-world data even in present-day performances. These approaches have broader significance when applied to understanding the impact of the historically low representation of females and minority groups in biomedical research on health outcomes.

Limits to sustained energy intake. XXXIV. Can the heat dissipation limit (HDL) theory explain reproductive aging?

According to the heat dissipation limit (HDL) theory, reproductive performance is limited by the capacity to dissipate excess heat. We tested the novel hypotheses that (1) the age-related decline in reproductive performance is due to an age-related decrease of heat dissipation capacity and (2) the limiting mechanism is more severe in animals with high metabolic rates. We used bank voles (Myodes glareolus) from lines selected for high swim-induced aerobic metabolic rate, which have also increased basal metabolic rate, and unselected control lines. Adult females from three age classes - young (4 months), middle-aged (9 months) and old (16 months) - were maintained at room temperature (20°C), and half of the lactating females were shaved to increase heat dissipation capacity. Old females from both selection lines had a decreased litter size, mass and growth rate. The peak-lactation average daily metabolic rate was higher in shaved than in unshaved mothers, and this difference was more profound among old than young and middle-aged voles (P=0.02). In females with large litters, milk production tended to be higher in shaved (least squares mean, LSM±s.e.: 73.0±4.74 kJ day-1) than in unshaved voles (61.8±4.78 kJ day-1; P=0.05), but there was no significan"t effect of fur removal on the growth rate [4.47±2.29 g (4 days-1); P=0.45]. The results provide mixed support of the HDL theory and no support for the hypotheses linking the differences in reproductive aging with either a deterioration in thermoregulatory capability or genetically based differences in metabolic rate.