Background: Testicular cancer, predominantly testicular germ cell tumours, is among the most common cancers in young men. Prenatal factors have been suggested to influence disease aetiology, but evidence regarding maternal smoking during pregnancy is inconsistent. We examined whether maternal smoking during pregnancy was associated with the risk of seminoma and non-seminoma in sons. Methods: We conducted a nationwide Danish cohort study using data from the Danish Medical Birth Register and the Danish Cancer Registry. The study included liveborn Danish males born from 1991 to 2009. Follow-up started from age 15 years until testicular cancer diagnosis, emigration, death, or 31 December 2024, whichever came first. Maternal smoking during pregnancy was obtained prospectively. Cox proportional hazards models with propensity score weights were used to estimate hazard ratios and 95% confidence intervals separately for seminoma and non-seminoma. Results: The final study population comprised 565,358 sons, of whom 126,133 (22.3%) had mothers who smoked during pregnancy, and 439,225 (77.7%) had non-smoking mothers. During follow-up, 641 testicular cancer cases were identified, including 239 seminomas and 395 non-seminomas. Maternal smoking during pregnancy was associated with a higher hazard of seminoma (HR: 1.27, 95% CI: 0.91-1.78) and a lower hazard of non-seminoma (HR: 0.81, 95% CI: 0.61-1.09), although neither estimate reached statistical significance. Conclusions: Maternal smoking during pregnancy was not significantly associated with testicular germ cell tumour risk overall, but the subtype-specific estimates suggested possible heterogeneity, with a tendency toward increased seminoma risk and decreased non-seminoma risk.

Cardiovascular diseases are the leading causes of mortality globally, of which coronary artery disease (CAD) is the most frequent. Several epigenomics and transcriptomics studies of CAD have been conducted, however, only a few studies have utilized the statically powerful discordant twin pair design, which reduces the confounding introduced by genetics. Finally, no study has investigated the link between the DNA methylation position and gene expression levels. The present study aims at filling this knowledge gap, to present novel biomarkers of CAD. We investigated 44 Danish twin pairs that were discordant for incident CAD, for whom, both genome-wide DNA methylation (CpG) and gene expression (probe) data were available. We identified CpGs and probes, which were more different within the twin pairs than expected by change, and investigated these by Cox regression analysis. CpGs and probes belonging to the same gene were divided into groups based on their directions of effect, and these genes were investigated by gene set enrichment and interaction network analyses. Overall, we found that CAD co-twins showed DNA methylation patterns leading to up-regulated gene expression; especially with demethylation of promoters and methylation of gene bodies, compared to their non-CAD co-twin. Generally, we found that the largest biological group of up-regulated pathways related to immune-inflammation processes, whereas down-regulated pathways related to muscle system biology, among others. Hence, the present study uncovers a specific pattern between DNA methylation position and gene expression levels relating to CAD, pointing to a need for additional studies. However, such multi-omics designs are surprisingly rare.

Background: Testicular cancer (TC) incidence has increased worldwide, but specific exposures of TC still need investigation. In this cohort study, we investigated the association between mothers' smoking and the risk of TC in their sons. TC was divided into the morphological subtype seminoma and non-seminomas. Because information about maternal smoking was not available in the study period maternal lung cancer diagnosis was used as a proxy for maternal smoking, making it possible for 51 years of complete follow-up. Methods: We used the nationwide Danish Cancer Registry and the Danish Civil Registration System to identify all mother-son pairs born from 1968 to 2005 (n = 1329,225). In 20,533 mother-son pairs, the mother was diagnosed with lung cancer, with 140 TC cases. 4136 TC cases were identified for 1308,693 mother-son pairs without lung cancer. Kaplan-Meier survival curves were used to show descriptive statistics for both morphological subtypes. We used Cox proportional hazards regression analysis to estimate the hazard ratio (HR) and 95 % CI for the association between a mother's lung cancer diagnosis and the risk of getting TC. Results: Men born by a mother developing lung cancer had an increased hazard of getting testicular cancer (HR=1.28, 95 % CI 1.08-1.51) when adjusting for maternal age at birth and maternal birth year. The results differ for seminomas (HR=1.52, 95 % CI 1.23-1.88) and non-seminomas (HR=0.97, 95 % CI 0.72-1.29). Conclusion: These findings, based on the long follow-up and nationwide data, suggest an increased risk of testicular cancer for seminomas in the sons of mothers with a lung cancer diagnosis, suggesting that smoking during pregnancy or in childhood could be associated with the son being diagnosed with testicular seminoma.

During aging, physical functioning declines, and disability and frailty increase; phenotypes which are bidirectionally linked. MicroRNAs (miRNAs) are epigenetic regulators of various physiological processes and suggested aging biomarkers. Here we investigate the association between circulating plasma miRNAs and hand grip strength, chair stand, (Rockwood) frailty, and activity of daily living (ADL) in 86 monozygotic twins (73-88 years). In cross-sectional analysis, both individual and twin-pair level analyses were performed, the latter controlling genetic confounding. The majority (74-100 %) of miRNAs identified in the individual-level analysis were validated by twin-pair-level analysis, with 14 miRNAs showing significance (p < 0.05) in both. Longitudinal analysis (up to eight years of follow-up) yielded more significant results (75-93 miRNAs), indicating that miRNAs might be more accurate in predicting functional decline over time. Of these miRNAs, seven showed consistent directions of effects across phenotypes. For all analyses, most (65-79 %) of the observed effect sizes were negative, reflecting reduced functionality with increased miRNA levels. Enrichment analyses revealed pathways of gene expression (incl. p53- and FOXO-mediated transcription), signal transduction, the immune system, metabolism of RNA, among others. Of specific miRNAs, miR-1274a demonstrated negative association in both cross-sectional and longitudinal investigations of ADL. These findings support miRNAs as biomarkers of age-related functional decline.

Objective: Mild cognitive impairment may be caused by pathophysiological changes occurring decades prior to symptom development. It has been hypothesised that oestrogen can prevent such changes. We aimed to investigate the association between postmenopausal hormone therapy and cognition in Danish female twins and to examine differences in this association before and after publication of the findings from the Women's Health Initiative study in 2002. Study design: This study includes cognitive assessment of 4510 twins aged 50+ years. Information on hormone therapy was obtained through Danish health registries. The association between current hormone therapy use and cognition was analysed in twins aged 50+ using both cross-sectional, intrapair and longitudinal analysis, adjusting for age, education, social class, and unobserved familial confounding. Results: Cross-sectionally, systemic HT users aged 70+ had a significantly lower cognitive function than nonusers, whereas systemic HT users aged 50-69 did not differ from non-users before 2002. Longitudinal data in younger twins aged 50-69 showed a significantly lower cognitive function in systemic HT users after 2002 compared to non-users. Systemic HT users aged 70+ showed that the lower cognitive function was most explicit before 2002, whereas after 2002 the cognitive function was closer to non-users. Twins aged 50-69 who changed from systemic HT to local HT after 2002, or dropped it altogether, performed cognitively better. Conclusions: Our findings cautiously indicate a change in the association between cognition and hormone therapy use after 2002, which suggests an alteration in the hormone therapy user profile in the wake of the 2002 WHI publication.

Mitochondrial dysfunction and genomic instability are key hallmarks of aging. The aim of this study was to evaluate whether maintenance of physical capacities at very old age is associated with key hallmarks of aging. To investigate this, we measured mitochondrial bioenergetics, mitochondrial DNA (mtDNA) copy number and DNA repair capacity in peripheral blood mononuclear cells from centenarians. In addition, circulating levels of NAD+/NADH, brain-derived neurotrophic factor (BDNF) and carbonylated proteins were measured in plasma and these parameters were correlated to physical capacities. Centenarians without physical disabilities had lower mitochondrial respiration values including ATP production, reserve capacity, maximal respiration and non-mitochondrial oxygen-consumption rate and had higher mtDNA copy number than centenarians with moderate and severe disabilities (p < 0.05). In centenarian females, grip strength had a positive association with mtDNA copy number (p < 0.05), and a borderline positive trend for activity of the central DNA repair enzyme, APE 1 (p = 0.075), while a negative trend was found with circulating protein carbonylation (p = 0.07) in the entire cohort. Lastly, a trend was observed for a negative association between BDNF and activity of daily living disability score (p = 0.06). Our results suggest that mechanisms involved in maintaining mitochondrial function and genomic stability may be associated with maintenance of physical function in centenarians.

Preserving cognitive function with age or super-aging greatly contributes to successful aging. Super-aging nonagenarians born in Denmark in either year 1905 or 1915 were classified as Cognitively High-Performing Oldest Old individuals with a five item cognitive composite score, equivalent to or better than mean middle-aged subjects. Cognitively high-performers were more physically active and had a better physical performance on e.g., Activity of Daily Living (p-value < 0.01), gait speed (p-value < 0.01) and grip strength (p-value < 0.05) compared with age-matched peers. Cognitive high-performing was also linked to lower depression symptomatology. When comparing super-agers with semi super-agers classified by Mini Mental State Examination > 27, super-agers were still more physically active and had a better physical performance (p-value < 0.05). Results suggests that physical activity is a lifestyle factor strongly associated with both semi and full cognitive super-aging.

The issue of "truncation by death" commonly arises in clinical research: subjects may die before their follow-up assessment, resulting in undefined clinical outcomes. To address this issue, we focus on survival-incorporated quantiles – quantiles of a composite outcome combining death and clinical outcomes – to summarize the effect of treatment. Using inverse probability of treatment weighting (IPTW), we propose an estimator for survival-incorporated quantiles from observational data, applicable to settings of both point treatment and time-varying treatments. We establish consistency and asymptotic normality of the estimator under both the true and estimated propensity scores. While the variance properties of IPTW estimators for the mean have been studied, to our knowledge, this article is the first to show that the IPTW quantile estimator using the estimated propensity score yields lower asymptotic variance than the IPTW quantile estimator using the true propensity score. Extensive simulations show that survival-incorporated quantiles provide a simple and useful summary measure and confirm that using the estimated propensity score reduces the root mean square error. We apply our method to estimate the effect of statins on the change in cognitive function, incorporating death, using data from the Long Life Family Study (LLFS) – a multicenter observational study of 4953 older adults with familial longevity. Our results indicate no significant difference in cognitive decline between statin users and non-users with a similar age- and sex-distribution at baseline. This study not only contributes to understand the cognitive effects of statins but also provides insights into analyzing clinical outcomes in the presence of death.

Weighing risks and benefits of postmenopausal hormone therapy (HT) has proven a balancing act. We aimed to investigate the association between HT and mortality before and after the 2002 publication from the Women’s Health Initiative (WHI) study. This publication found that the risk of using HT outweighted the benefits, and thus it caused a marked reduction in systemic HT user prevalence. The 2002 WHI publication may also have caused a change in the subsequent HT user profile, as HT is no longer recommended in the prevention of chronic diseases. This cohort study included two populations followed from 1995: A 5% random sample of female singletons from the Danish general population (n = 52,388) and a sample of Danish female twins (n = 15,261). HT use was evaluated in 1995, 2000, 2005, and 2010. The association between HT, education, and mortality was investigated and controlled for potential unobserved familial confounding in a within-pair analysis. Singletons aged 56–75 using systemic HT in 2000 had a lower mortality compared to non-users (hazard ratio (HR) 0.83, 95% confidence interval (CI) 0.78–0.89). In 2005, the mortality was like that of the background population for this age group (HR 1.02, 95% CI 0.94–1.11). Recently postmenopausal twins showed a similar tendency. Systemic HT users, who had switched to local HT by 2005, had a substantially lower mortality than non-users (HR ranging from 0.42 to 0.67 depending on age group). In conclusion, we found that the prevalence of systemic HT use declined after 2002, and systemic HT users’ mortality changed from lower before 2002 to similar to that of the background population after 2002. This indicates that the healthiest users decided to either drop systemic HT or switcted to local HT, as recommendations changed following the WHI publication.

Objective: The effect of systemic hormone therapy (HT) on dementia risk is unclear. Our aim was to investigate the association between HT and dementia. Study design: This register-based study consists of a nested case-control study and a co-twin control design, which controls for familial confounding, including shared genetics. Main outcome measures: Through Danish national registries from 1995 to 2011, we identified: a) 2700 female singletons with incident dementia and 13,492 matched controls; b) 288 female twins with incident dementia and co-twins without dementia. Data on HT and education were retrieved, and analyses were performed using conditional logistic regression and McNemar's chi(2)-test. HT use decreased dramatically after the Women's Health Initiative study results were published in 2002, and the analyses were stratified accordingly to account for potentially different HT user characteristics. Results: The odds ratio (OR) for the association between systemic HT and dementia was 1.05, 95% CI = [0.93-1.19] in singletons and 2.10, 95% CI = [0.99-4.46] in twins. A statistically significant association was found for systemic HT before 2003 in both populations, with an OR of 1.14, 95% CI = [1.01-1.28] in singletons and an OR of 2.20, 95% CI = [1.04-4.65] in twins. Conclusion: Using Danish nationwide registries and controlling for education and for familial factors in a subsample, systemic HT was found to be associated with increased dementia risk if used before 2003, when HT was more commonly prescribed.

BACKGROUND:Previous research has suggested that individuals with Type 2 diabetes and initiated on metformin monotherapy present with a survival advantage compared with the general population without diabetes. This finding has generated considerable interest in the prophylactic use of metformin against age-related morbidity.METHODS:Utilizing Danish National Health Registers, we assessed differences in survival associated with metformin monotherapy for Type 2 diabetes compared with no diagnosis of diabetes in both singleton and discordant twin populations between 1996 and 2012. Data were analysed in both nested case-control and matched cohort study designs, with incidence rate ratios (IRRs) and hazard ratios estimated using conditional logistic regression and Cox proportional hazards regression, respectively.RESULTS:In case-control pairs matched on birth year and sex or co-twin (sex, birth year and familial factors), incident Type 2 diabetes with treatment by metformin monotherapy initiation compared with no diagnosis of diabetes was associated with increased mortality in both singletons (IRR = 1.52, 95% CI: 1.37, 1.68) and discordant twin pairs (IRR = 1.90, 95% CI: 1.35, 2.67). After adjusting for co-morbidities and social indicators, these associations were attenuated to 1.32 (95% CI: 1.16, 1.50) and 1.64 (95% CI: 1.10, 2.46), respectively. Increased mortality was observed across all levels of cumulative use and invariant to a range of study designs and sensitivity analyses.CONCLUSIONS:Treatment initiation by metformin monotherapy in Type 2 diabetes was not associated with survival equal or superior to that of the general population without diabetes. Our contrasting findings compared with previous research are unlikely to be the result of differences in epidemiological or methodological parameters.

Background The existence of a super-select group of centenarians that demonstrates increased survivorship has been hypothesized. However, it is unknown if this super-select group possesses similar characteristics apart from extreme longevity. Methods In this study, we analyse high-quality health and survival data of Danish centenarians born in 1895, 1905 and 1910. We use Latent Class Analysis to identify unobserved health classes and to test whether these super-select lives share similar health characteristics. Results We find that, even after age 100, a clear and distinct gradient in health exists and that this gradient is remarkably similar across different birth cohorts of centenarians. Based on the level of health, we identify three clusters of centenarians - robust, frail and intermediate - and show that these groups have different survival prospects. The most distinctive characteristic of the robust centenarians is the outperformance in different health dimensions (physical, functional and cognitive). Finally, we show that our health class categorizations are good predictors of the survival prospects of centenarians. Conclusions There is a clear stratification in health and functioning among those over 100 years of age and these differences are associated with survival beyond age 100.

Background The existence of a super-select group of centenarians that demonstrates increased survivorship has been hypothesized. However, it is unknown if this super-select group possesses similar characteristics apart from extreme longevity. Methods In this study, we analyse high-quality health and survival data of Danish centenarians born in 1895, 1905 and 1910. We use Latent Class Analysis to identify unobserved health classes and to test whether these super-select lives share similar health characteristics. Results We find that, even after age 100, a clear and distinct gradient in health exists and that this gradient is remarkably similar across different birth cohorts of centenarians. Based on the level of health, we identify three clusters of centenarians - robust, frail and intermediate - and show that these groups have different survival prospects. The most distinctive characteristic of the robust centenarians is the outperformance in different health dimensions (physical, functional and cognitive). Finally, we show that our health class categorizations are good predictors of the survival prospects of centenarians. Conclusions There is a clear stratification in health and functioning among those over 100 years of age and these differences are associated with survival beyond age 100.

Neurofilament light chain (NfL) has emerged as a promising blood biomarker for the progression of various neurological diseases. NfL is a structural protein of nerve cells, and elevated NfL levels in blood are thought to mirror damage to the nervous system. We find that plasma NfL levels increase in humans with age (n=122; 21-107 years of age) and correlate with changes in other plasma proteins linked to neural pathways. In centenarians (n=135), plasma NfL levels are associated with mortality equally or better than previously described multi-item scales of cognitive or physical functioning, and this observation was replicated in an independent cohort of nonagenarians (n=180). Plasma NfL levels also increase in aging mice (n=114; 2-30 months of age), and dietary restriction, a paradigm that extends lifespan in mice, attenuates the age-related increase in plasma NfL levels. These observations suggest a contribution of nervous system functional deterioration to late-life mortality.

Background Mortality rates have been reduced by half over the last 60 years for nonagenarians, and the progress is continuing. The greater survival might be due to overtreatment of severely physically and cognitively disabled individuals, which is a big concern for societies and individuals. Methods The study population comprised two Danish birth cohorts: the 1905 Cohort and the 1915 Cohort. At age 95, all from the two cohorts who were still alive and living in Denmark were invited to participate in a health survey that used the same assessment instrument. A total of 2,670 (56.8%) persons participated in the two surveys and survival was assessed through a 7.3-year follow-up period during which 2,497 (93.5%) had died, and with virtually no loss to follow-up. Results Despite the increasing chance of surviving to age 95, the 1915 Cohort had significantly better health and functioning than the 1905 Cohort. The survival advantage in the 1915 Cohort continued in the follow-up period after age 95: Median survival length was 2.4 months longer, p = .011. This advantage was not statistically associated with different levels of activities of daily living, physical performance, cognitive functioning, self-rated health and life satisfaction. However, the advantage tended to be more pronounced among people with better health. Conclusions Life span and health increases among the oldest old. The improvement in survival for 95-year olds born in 1915 compared with 1905 was seen across the whole spectrum of health and functioning, with a tendency towards bigger improvement among those in good health.

BACKGROUNDTransient cognitive impairment is common in adult patients of all ages following anaesthesia and surgery. Apolipoprotein E (APOE) ε4 carriers may have a larger deterioration in short-term cognitive function after major surgery compared with APOE ε4 noncarriers.OBJECTIVESThe aim was to examine the effect of APOE ε4 on the association between exposure to surgery and anaesthesia, and subsequent cognitive functioning. A more pronounced deterioration in cognitive function in APOE ε4 carriers was hypothesised.DESIGNAn observational cross-sectional and a 6 to 10 years longitudinal twin cohort design.SETTINGSurvey and register study of 2936 Danish twins aged 45 to 92 years.MAIN OUTCOME MEASURESCognitive function was assessed using five age-sensitive cognitive tests. In the cross-sectional study, we compared twins exposed to surgery with a reference group (unexposed). Linear regression models were used adjusting for sex and age and stratified by APOE ε4 carrier status. In the longitudinal cognitive follow-up study 1671 twins participated. Intrapair analyses were also performed using 70 same-sexed twin pairs concordant for APOE ε4 carrier status, but discordant for major surgery.RESULTSAPOE ε4 carriers had lower cognitive scores compared with noncarriers, and this was statistically significant in elderly twins 70+ years of age (mean difference, −0.67; 95% CI, −1.14 to −0.17). There was no significant impact on cognitive function after surgery according to APOE ε4 carrier status in the cross-sectional study. Similarly, there was no APOE ε4 modification in the longitudinal study. Also, in the intrapair analyses no evidence was found of lower cognitive score after major surgery compared with the nonexposed cotwins among APOE ε4 carriers.CONCLUSIONNo evidence was found of more pronounced long-term deterioration in cognitive function after surgery among APOE ε4 carriers, but elderly APOE ε4 carriers in general performed worse on the cognitive tests than noncarriers.

BackgroundThe adverse association between income, health and survival is well documented, but little is known about how income trajectories influence health and survival for men and women. We aim to investigate sex differences in mortality and hospitalisations by income and income changes.MethodsWe performed a population-based, nationwide study including 1 063 787 Danes born 1935–1955 and residing in Denmark during 1980–2015. Income was calculated during two age intervals: 45–49 and 55–59 years. The average income was divided into quartiles for men and women separately, which formed the basis for the income trajectories. Individuals were followed up from age 60 until 2014/2015 for hospital admission and mortality, respectively.ResultsMen had higher mortality and were more hospitalised than women. Sex differences in mortality were most pronounced for people with stable low income (relative difference in hazard=1.93; 95% CI 1.89 to 1.98) and a downward income trajectory (1.91; 95% CI 1.85 to 1.98) with smaller sex differences for people with an upward trajectory (1.59; 95% CI 1.56 to 1.62) and stable high income (1.37; 95% CI 1.33 to 1.41). A similar pattern was found for family income. Regarding hospitalisations, similar results were found, though less pronounced. Investigation of mortality and hospitalisations by all possible trajectories demonstrated that income at ages 55–59 was an important predictor of mortality, with increasing mortality for decreasing income quartile.ConclusionIncome trajectories as a proxy for change in social position have a larger influence on men’s than women’s health and mortality. Income in the late 50s is an important predictor of mortality, particularly for men.

One of the possibilities to assess differences between monozygotic (MZ) twins, theoretically identical, is the perceived age as an estimate of biological age between MZ pairs. When we consider a lifelong exposure to environmental influences and insults of any sort, the initial more pronounced similarity between MZ twins will increasingly diverge with age. Despite the high heritability in perceived age, there is still a big absolute intrapair variation in this parameter between MZ twin pairs. Still the intrapair correlation was high even after age 70. Using data derived from the Danish Twin Registry, the authors investigated the relative influence of genetic and environmental factors on aging phenotypes. This chapter focuses on perceived age of MZ twins older than 70 years as a biomarker of aging and discuss how perceived age is associated with health and survival.

To examine sex differences in prevalent comorbidity and frailty across age and European regions. This is a cross-sectional study based on 113,299 Europeans aged 50+ participating in the Survey of Health, Ageing and Retirement in Europe from 2004–2005 to 2015. Sex differences in the Comorbidity Index and the Frailty Phenotype were investigated using ordinal logistic regressions. European women had generally higher odds of prevalent comorbidity (OR 1.11, 95% CI 1.07–1.15) and frailty (OR 1.56, 95% CI 1.51–1.62). Sex differences increased with advancing age. No overall sex difference in comorbidity was found in Western Europe, but women had more comorbidity than men in Eastern (OR 1.30, 95% CI 1.18–1.44), Southern (OR 1.23, 95% CI 1.15–1.30), and Northern (OR 1.08, 95% CI 1.01–1.16) Europe. Women were frailer than men in all regions, with the largest sex difference in Southern Europe (OR 1.84, 95% CI 1.72–1.96). European women are frailer and have slightly more comorbidity than European men lending support for the male–female health survival paradox.