A Federated Database for Obesity Research: An IMI-SOPHIA Study

Obesity is considered by many as a lifestyle choice rather than a chronic progressive disease. The Innovative Medicines Initiative (IMI) SOPHIA (Stratification of Obesity Phenotypes to Optimize Future Obesity Therapy) project is part of a momentum shift aiming to provide better tools for the stratification of people with obesity according to disease risk and treatment response. One of the challenges to achieving these goals is that many clinical cohorts are siloed, limiting the potential of combined data for biomarker discovery. In SOPHIA, we have addressed this challenge by setting up a federated database building on open-source DataSHIELD technology. The database currently federates 16 cohorts that are accessible via a central gateway. The database is multi-modal, including research studies, clinical trials, and routine health data, and is accessed using the R statistical programming environment where statistical and machine learning analyses can be performed at a distance without any disclosure of patient-level data. We demonstrate the use of the database by providing a proof-of-concept analysis, performing a federated linear model of BMI and systolic blood pressure, pooling all data from 16 studies virtually without any analyst seeing individual patient-level data. This analysis provided similar point estimates compared to a meta-analysis of the 16 individual studies. Our approach provides a benchmark for reproducible, safe federated analyses across multiple study types provided by multiple stakeholders.

Health care system efficiency and life expectancy: A 140-country study

Despite the evidence of links between health expenditure and health care efficiency, it is still unclear why countries with similar levels of health expenditures experience different outputs in terms of life expectancy at birth. Health care system efficiency might shed some light on the question. Using output-oriented data envelopment analysis, we compared the health systems of 140 countries in terms of attained life expectancy. Efficiency is determined by the distance from the closest country on the best practice frontier, which identifies the highest attainable life expectancy observed for any given level of health care spending. By using national data form the Human Development Data, we built the efficiency frontier and computed the potential life expectancy increase for each country. The potential improvement was, on average, 5.47 years [95%CI: 4.71-6.27 years]. The least efficient countries (10th percentile of the efficiency score) could improve by 11.78 years, while the most efficient countries (90th percentile of the efficiency score) could only improve by 0.83 years. We then analyzed, with regression analysis stratified by average education level, and by the role of health-related variables in differentiating efficient and inefficient countries from each other. The results suggest that, among countries with lower levels of education, decreasing unemployment and income inequality increases average life expectancy, without increasing health expenditure levels.

Two stochastic processes shape diverse senescence patterns in a single-cell organism

Despite advances in aging research, a multitude of aging models, and empirical evidence for diverse senescence patterns, understanding of the biological processes that shape senescence is lacking. We show that senescence of an isogenic Escherichia coli bacterial population results from two stochastic processes. The first process is a random deterioration process within the cell, such as generated by random accumulation of damage. This primary process leads to an exponential increase in mortality early in life followed by a late age mortality plateau. The second process relates to the stochastic asymmetric transmission at cell fission of an unknown factor that influences mortality. This secondary process explains the difference between the classical mortality plateaus detected for young mothers' offspring and the near nonsenescence of old mothers' offspring as well as the lack of a mother-offspring correlation in age at death. We observed that lifespan is predominantly determined by underlying stochastic stage dynamics. Surprisingly, our findings support models developed for metazoans that base their arguments on stage-specific actions of alleles to understand the evolution of senescence. We call for exploration of similar stochastic influences that shape aging patterns beyond simple organisms.

Effect of dietary canthaxanthin and iodine on the production performance and egg quality of laying hens

In this study, we aimed to evaluate the effect of canthaxanthin (CX) and iodine (I) on the production of laying hens, on counteracting debilitation of the vitelline membrane, and on inhibiting Salmonella growth in eggs stored at 30°C. Three hundred hens were reared in cages. Birds were divided into six feeding groups (10 hens × 5 repetitions) that were administered 0, 3 or 6 ppm of CX and 1 or 10 ppm of I with their diets. Laying rate, egg weights, and feed conversion ratios were controlled. The quality of fresh eggs was assessed in wks 25-26, 48-50 and 62-63 of hens lives. An additional batch of eggs was incubated at the temperature of 30°C, and egg quality changes were monitored on days 3, 6 and 9 of storage. Additionally, eggs collected from four experimental groups of hens whose diets had been iodated with 1 or 10 ppm of I and supplemented with 0 or 6 ppm of CX were infected under laboratory conditions with Salmonella, and incubated for 5 and 10 d. The laying rate, egg weights, and feed conversion ratio were significantly improved. Dietary inclusion of CX contributed to a higher resistance of the vitelline membrane of egg yolks, but only for fresh eggs. Vitelline membrane degradation during egg storage at 30°C was significantly counteracted by dietary inclusion of I at a dose of 10 ppm. The same I dose resulted in the complete inhibition of Salmonella growth until day 10 of incubation, but exclusively for eggs collected from 40-week-old hens. Dietary supplementation with 10 ppm of I was found to impart high level of resistance to the vitelline membrane against the growth of Salmonella in case of eggs stored at 30°C; therefore, I was found to be more beneficial by ensuring longer preservation than that of CX. However, dietary supplementation with CX was found to increase the resistance of vitelline membrane in fresh eggs.

Complexity of the relationship between life expectancy and overlap of lifespans

Longevity has long been recognised as a key facilitator of reciprocal altruism because repeated cooperation of partners hinges on mutual survival. Although demographic tools can be used to quantify mutual survival and expected overlapping lifespans, studies on the evolutionary theory of cooperation take only limited advantage of demography. Overlap of lifespans depends on variation in survival across ages and can be high or low independently of high or low life expectancies. Here we develop formal demographic measures to study the complex relationships between shared life expectancy of two birth cohort peers, the proportion of their lives that they can expect to overlap, and longevity. We simulate age-specific mortality schedules using a Siler model to reveal how infant and senescent mortality, along with age-independent mortality, affect the relationship between the proportion of life shared and life expectancy. We find that while the proportion of life shared can vary vastly for similar life expectancies, almost all changes to mortality schedules that result in higher life expectancies also result in higher proportions of life shared. A distinct exception occurs if life expectancy increases due to lowering the rate of senescence. In this case the proportion of life shared decreases. Our work shows that almost all selective pressures that result in higher life expectancies also result in a larger proportion of life shared. Therefore, selective forces that extend life also improve the chances that a cooperative system would be stable in terms of reciprocal interactions. Since reciprocal interactions may also reduce mortality and result in a feedback loop with the evolution of longevity, our measures and findings can be used for future cross-species comparisons that aim to disentangle predecessor and successor in the evolution of longevity and cooperation.

Blood DNA methylation age is not associated with cognitive functioning in middle-aged monozygotic twins

The epigenetic clock, also known as DNA methylation age (DNAmAge), represents age-related changes of DNA methylation at multiple sites of the genome and is suggested to be a biomarker for biological age. Elevated blood DNAmAge is associated with all-cause mortality, with the strongest effects reported in a recent intrapair twin study where epigenetically older twins had increased mortality risk in comparison to their co-twins. In the study presented here, we hypothesize that DNAmAge in blood is associated with cross-sectional and longitudinal cognitive abilities in middle-aged individuals. In 486 monozygotic twins, we investigated the association of DNAmAge, difference between DNAmAge and chronological age and age acceleration with cognition. Despite using a powerful paired twin design, we found no evidence for association of blood DNAmAge with cognitive abilities. This observation was confirmed in unpaired analyses, where DNAmAge initially correlated with cognitive abilities, until adjusting for chronological age. Overall, our study shows that for middle-aged individuals DNAmAge calculated in blood does not correlate with cognitive abilities.

DNA methylation age is associated with mortality in a longitudinal Danish twin study

An epigenetic profile defining the DNA methylation age (DNAm age) of an individual has been suggested to be a biomarker of aging, and thus possibly providing a tool for assessment of health and mortality. In this study, we estimated the DNAm age of 378 Danish twins, age 30–82 years, and furthermore included a 10‐year longitudinal study of the 86 oldest‐old twins (mean age of 86.1 at follow‐up), which subsequently were followed for mortality for 8 years. We found that the DNAm age is highly correlated with chronological age across all age groups (r = 0.97), but that the rate of change of DNAm age decreases with age. The results may in part be explained by selective mortality of those with a high DNAm age. This hypothesis was supported by a classical survival analysis showing a 35% (4–77%) increased mortality risk for each 5‐year increase in the DNAm age vs. chronological age. Furthermore, the intrapair twin analysis revealed a more‐than‐double mortality risk for the DNAm oldest twin compared to the co‐twin and a ‘dose–response pattern’ with the odds of dying first increasing 3.2 (1.05–10.1) times per 5‐year DNAm age difference within twin pairs, thus showing a stronger association of DNAm age with mortality in the oldest‐old when controlling for familial factors. In conclusion, our results support that DNAm age qualifies as a biomarker of aging.

Gompertz-Makeham life expectancies: expressions and applications

In a population of individuals, whose mortality is governed by a Gompertz-Makeham hazard, we derive closed-form solutions to the life-expectancy integral, corresponding to the cases of homogeneous and gamma-heterogeneous populations, as well as in the presence/absence of the Makeham term. Derived expressions contain special functions that aid constructing high-accuracy approximations, which can be used to study the elasticity of life expectancy with respect to model parameters. Knowledge of Gompertz-Makeham life expectancies aids constructing life-table exposures.