Sex Differences in Genetic Associations With Longevity

IMPORTANCE

Sex differences in genetic associations with human longevity remain largely unknown; investigations on this topic are important for individualized health care.

OBJECTIVE

To explore sex differences in genetic associations with longevity.

DESIGN SETTING AND PARTICIPANTS

This population-based case-control study used sex-specific genome-wide association study and polygenic risk score (PRS) analyses to examine sex differences in genetic associations with longevity. Five hundred sixty-four male and 1614 female participants older than 100 years were compared with a control group of 773 male and 1526 female individuals aged 40 to 64 years. All were Chinese Longitudinal Healthy Longevity Study participants with Han ethnicity who were recruited in 1998 and 2008 to 2014.

MAIN OUTCOMES AND MEASURES

Sex-specific loci and pathways associated with longevity and PRS measures of joint effects of sex-specific loci.

RESULTS

Eleven male-specific and 11 female-specific longevity loci (P < 10-5) and 35 male-specific and 25 female-specific longevity loci (10-5 ≤ P < 10-4) were identified. Each of these loci's associations with longevity were replicated in north and south regions of China in one sex but were not significant in the other sex (P = .13-.97), and loci-sex interaction effects were significant (P < .05). The associations of loci rs60210535 of the LINC00871 gene with longevity were replicated in Chinese women (P = 9.0 × 10-5) and US women (P = 4.6 × 10-5) but not significant in Chinese and US men. The associations of the loci rs2622624 of the ABCG2 gene were replicated in Chinese women (P = 6.8 × 10-5) and European women (P = .003) but not significant in both Chinese and European men. Eleven male-specific pathways (inflammation and immunity genes) and 34 female-specific pathways (tryptophan metabolism and PGC-1α induced) were significantly associated with longevity (P < .005; false discovery rate < 0.05). The PRS analyses demonstrated that sex-specific associations with longevity of the 4 exclusive groups of 11 male-specific and 11 female-specific loci (P < 10-5) and 35 male-specific and 25 female-specific loci (10-5 ≤P < 10-4) were jointly replicated across north and south discovery and target samples. Analyses using the combined data set of north and south showed that these 4 groups of sex-specific loci were jointly and significantly associated with longevity in one sex (P = 2.9 × 10-70 to 1.3 × 10-39) but not jointly significant in the other sex (P = .11 to .70), while interaction effects between PRS and sex were significant (P = 4.8 × 10-50 to 1.2 × 10-16).

CONCLUSION AND RELEVANCE

The sex differences in genetic associations with longevity are remarkable, but have been overlooked by previously published genome-wide association studies on longevity. This study contributes to filling this research gap and provides a scientific basis for further investigating effects of sex-specific genetic variants and their interactions with environment on healthy aging, which may substantially contribute to more effective and targeted individualized health care for male and female elderly individuals.

How long do centenarians survive? Life expectancy and maximum lifespan

OBJECTIVES

The purpose of this study was to explore the pattern of mortality above the age of 100 years. In particular, we aimed to examine whether Scandinavian data support the theory that mortality reaches a plateau at particularly old ages. Whether the maximum length of life increases with time was also investigated.

METHODS

The analyses were based on individual level data on all Swedish and Danish centenarians born from 1870 to 1901; in total 3006 men and 10 963 women were included. Birth cohort-specific probabilities of dying were calculated. Exact ages were used for calculations of maximum length of life. Whether maximum age changed over time was analysed taking into account increases in cohort size.

RESULTS

The results confirm that there has not been any improvement in mortality amongst centenarians in the past 30 years and that the current rise in life expectancy is driven by reductions in mortality below the age of 100 years. The death risks seem to reach a plateau of around 50% at the age 103 years for men and 107 years for women. Despite the rising life expectancy, the maximum age does not appear to increase, in particular after accounting for the increasing number of individuals of advanced age.

CONCLUSION

Mortality amongst centenarians is not changing despite improvements at younger ages. An extension of the maximum lifespan and a sizeable extension of life expectancy both require reductions in mortality above the age of 100 years.

Pre-analytical stability of the plasma proteomes based on the storage temperature

Background

This study examined the effect of storage temperature on the protein profile of human plasma. Plasma samples were stored for 13 days at -80°C, -20°C, +4°C and room temperature (20-25°C) prior to proteomic analysis. The proteomic comparisons were based on the differences of mean intensity values of protein spots between fresh plasma samples (named “time zero”) and plasma samples stored at different temperatures. To better understand the thermally induced biochemical changes that may affect plasma proteins during storage we identified proteins with different expressions with respect to the time zero sample.

Results

Using two-dimensional electrophoresis followed by MALDI-TOF MS and /or LC-MS/MS 20 protein spots representing 10 proteins were identified with significant differences in abundance when stored at different temperatures. Our results, in agreement with various authors, indicate that during storage for a short period (13 days) at four different temperatures plasma proteins were more affected by degradation processes at +4°C compared to the other temperatures analysed. However, we founded that numerous protein spots (vitamin D binding protein, alpha-1-antitrypsin, serotransferrin, apoplipoprotein A-I, apolipoprotein E, haptoglobin and complement factor B) decrease in abundance with increasing temperature up to 4°C, but at room temperature their intensity mean values are similar to those of time zero and -80°C. We hypothesize that these proteins are labile at 4°C, but at the same time they are stable at room temperature (20-25°C). Furthermore we have grouped the proteins based on their different sensitivity to the storage temperature. Spots of serum albumin, fibrinogen gamma chain and haptoglobin are more resistant to the higher temperatures tested, as they have undergone changes in abundance only at room temperature; conversely, other spots of serum albumin, fibrinogen beta chain and serotransferrin are more labile as they have undergone changes in abundance at all temperatures except at -80°C.

Conclusions

Although there are many studies concerning protein stability of clinical samples during storage these findings may help to provide a better understanding of the changes of proteins induced by storage temperature.

Activity of mannose-binding lectin in centenarians

We analyzed MBL2 gene variants in two cohorts of centenarians, octo-nonagenarians and nonagenarians, and in the general population, one from Sardinia Island (Italy), recruited in the frame of the AKea study, and another from Campania (southern Italy), to search for haplotypes related to longevity. We also assessed in vitro the effect of mannose-binding lectin (MBL) on various human cells at different stage of senescence. The frequency of high and null activity haplotypes was significantly lower, and the frequency of intermediate activity haplotype significantly higher in centenarians and in subjects between 80 and 99 years from both the cohorts as compared each to the general population from the same geographic area. Furthermore, serum MBL concentration (also after normalization to serum albumin) was significantly lower in centenarians and in octo- and nonagenarians as compared to the general population, suggesting that intermediate MBL haplotype/activity may be protective. We also demonstrated that in vitro MBL protein bound to senescent IMR90 fibroblasts thereby causing cell lysis, but not to other types of cycle-arrested cells not in senescence. This implicates a novel role of MBL in the clearance of senescent cells.

Apolipoprotein E Genotypes: Relationship to Cognitive Functioning, Cognitive Decline, and Survival in Nonagenarians

OBJECTIVES

To evaluate the extent to which relationships between apolipoprotein E, cognitive functioning, and survival in people aged 60 to 80 persist into advanced old age.

DESIGN

Examine the effect of apolipoprotein E genotypes on baseline cognitive functioning, cognitive decline over 5 years, and survival in a cohort of 1,551 nonagenarians.

SETTING

The Danish 1905 birth cohort.

PARTICIPANTS

One thousand five hundred fifty-one nonagenarians from the Danish 1905 birth cohort.

MEASUREMENTS

Cognitive functioning was assessed using the Mini-Mental State Examination (MMSE) and five brief cognitive tests (cognitive composite).

RESULTS

The subjects were stratified into four groups by occurrence of a protective (epsilon2) or a risk (epsilon4) apo E allele (epsilon22 and epsilon23, epsilon33, epsilon24 and epsilon34, epsilon44). At intake, the mean scores for the three genotype groups were 22.1, 21.8, 21.4, and 21.0 for MMSE and 0.10, 0.07, -0.02, and 0.30 for the cognitive composite, respectively. Growth-curve analyses showed that, although individuals carrying at least one epsilon4 allele had slightly lower MMSE scores and declined slightly more rapidly over time, this effect was not statistically significant and was not apparent in scores on the cognitive composite. In subjects whose functioning was relatively well preserved (those still living and able to participate in the assessment, and whose cognitive functioning had declined less than 4 points on the MMSE), epsilon4 frequencies tended to decline at subsequent waves (P=.03, chi-square test for trend), but epsilon4 had no significant survival disadvantage (hazard ratio=1.11 (95% confidence interval=0.99-1.25; P=.07).

CONCLUSION

Apo E genotype has a small effect on the probability of remaining a well-functioning nonagenarian but no separately detectable effect on cognitive functioning, cognitive decline, or survival.

No evidence for an association between extreme longevity and microsomal transfer protein polymorphisms in a longitudinal study of 1651 nonagenarians

Previous studies have reported two SNPs and a haplotype marker within the Microsomal Transfer Protein gene associated with extreme longevity. Here, we test this finding in a longitudinal study of nonagenarians and in an association study. Participants in the Danish 1905 cohort study (1651 participants aged 92-93 years) were genotyped for the two SNPs (rs2866164 and Q95H) in the Microsomal Transfer Protein gene recently reported to be associated with longevity. The 1905 Cohort has been followed for 6.5 years, during which period 83% of the cohort has died. Furthermore, a group of 575 middle-aged Danish twins (mean age 53.7 years) were tested as a younger control group. The risk haplotype had no significant survival disadvantage (P-values: 0.56, 0.31 and 0.97 in the total population of nonagenarians, males and females, respectively) after 6.5 years of follow-up. The distributions of the suggested risk alleles (rs2866164-G and Q95) and the resulting haplotypes are very similar and not statistically different between the two age cohorts. The frequency for rs2866164-G is in the middle-aged compared to the nonagenarians 25.4 and 23.6% in males and 23.0 and 26.1% in females. The frequency for the risk haplotype is in the middle-aged compared to the nonagenarians 22.7 and 19.2% in males and 18.1 and 21.8% in females. In conclusion, our longitudinal study of survival in the 10th decade of life and an association study in a genetically homogeneous population provided no support for an association between the Microsomal Transfer Protein gene and extreme longevity.

Association of late childbearing with healthy longevity among the oldest-old in China

Statistical analysis of a large and unique longitudinal data-set demonstrates that childbearing after age 35 or 40 is associated with survival and healthy survival among very old Chinese women and men. The association is stronger for women than for men. The estimates are adjusted for a variety of confounding factors: demographic characteristics, family support, social connections, health practices, and health conditions. Further analysis based on an extension of the Fixed-Attributes Dynamics method shows that late childbearing is positively associated with long-term survival and healthy survival from ages 80-85 to 90-95 and 100-105. This association exists among oldest-old women and men, but, again, the effects are substantially stronger for women than for men. We discuss four possible factors that may explain why late childbearing affects healthy longevity at advanced ages: (1) social factors; (2) biological changes caused by late pregnancy and delivery; (3) genetic and other biological characteristics; and (4) selection.

Association of mutations in the hemochromatosis gene with shorter life expectancy

BACKGROUND

To investigate whether the frequency of carriers of mutations in the HFE gene associated with hereditary hemochromatosis diminishes with age as an indication that HFE mutations are associated with increased mortality. It is of value in the debate concerning screening for hereditary hemochromatosis to determine the significance of heterozygosity.

METHODS

Genotyping for mutations in exons 2 and 4 of the HFE gene using denaturing gradient gel electrophoresis in 1784 participants aged 45 to 100 years from 4 population-based studies: all 183 centenarians from the Danish Centenarian Study, 601 people aged 92 to 93 years from the Danish 1905 Cohort, 400 aged 70 to 94 years from the Longitudinal Study of Aging Danish Twins, and 600 aged 45 to 67 years from a study of middle-aged Danish twins.

RESULTS

All participants (N=1784) were screened for mutations in exon 4, and a trend toward fewer heterozygotes for the C282Y mutation-the mutation most often associated with hereditary hemochromatosis-was found. This was significant for the whole population (P=.005) and for women (P=.004) but not for men (P=.26). A group of 599 participants was screened for mutations in exon 2, and there was no variation in the distribution of mutations in exon 2 in the different age groups.

CONCLUSIONS

In a high-carrier frequency population like Denmark, mutations in HFE show an age-related reduction in the frequency of heterozygotes for C282Y, which suggests that carrier status is associated with shorter life expectancy.

Evidence for a Substantial Genetic Influence on Biochemical Liver Function Tests: Results from a Population-based Danish Twin Study

Background: Biochemical liver function tests are widely used in the clinic and are some of the most frequently used tests in screening for diseases in older age groups. The aim of the present study was to estimate the relative importance of genetic and environmental factors to variations in these tests among the elderly.

Methods: We conducted a survey among Danish twins, 73–102 years of age, identified in the population-based Danish Twin Registry. Among the 2749 individuals in the study population, an interview was conducted with 79%. From these, a blood sample was collected from 290 same-sex twin pairs, total of 580 subjects, within a 6-month period and analyzed for alanine aminotransferase (ALT), lactate dehydrogenase (LDH), γ-glutamyltransferase (GGT), bilirubin, and albumin. The interview included questions about alcohol consumption and body mass index (BMI; self-calculated height and weight). Heritability (proportion of the population variance attributable to genetic variation) was estimated using structural-equation analyses before and after correction for alcohol consumption and BMI.

Results: Structural-equation analyses revealed a substantial heritability (35–61%) for the four biochemical liver function tests: ALT, GGT, LDH, and bilirubin. The remaining variation could be attributed to individuals’ nonfamilial environments. Adjustment for alcohol consumption and BMI had no influence on the heritability for ALT, GGT, LDH, and bilirubin. For albumin, two models fit equally well before adjustment for alcohol and BMI: a model including additive genetic and nonshared environmental factors (AE), and a model including shared and nonshared environmental factors (CE). After adjustment, the model including shared and nonshared environment was clearly the best fitting model.

Conclusions: For both males and females, the effect of genetic factors on the biochemical liver function tests ALT, GGT, LDH, and bilirubin is substantial and accounts for one-third to two-thirds of the variation among individuals 73–102 years of age. The heritability is equal for males and females and does not change notably after controlling for alcohol consumption and BMI. For albumin, no major impact of genetic factors was found independent of BMI and alcohol consumption. An understanding of the genetic mechanisms underlying biochemical liver function tests among the very old may be of value in the interpretation of these tests in this age group.

Evidence for a substantial genetic influence on biochemical liver function tests: results from a population-based Danish twin study

BACKGROUND

Biochemical liver function tests are widely used in the clinic and are some of the most frequently used tests in screening for diseases in older age groups. The aim of the present study was to estimate the relative importance of genetic and environmental factors to variations in these tests among the elderly.

METHODS

We conducted a survey among Danish twins, 73-102 years of age, identified in the population-based Danish Twin Registry. Among the 2749 individuals in the study population, an interview was conducted with 79%. From these, a blood sample was collected from 290 same-sex twin pairs, total of 580 subjects, within a 6-month period and analyzed for alanine aminotransferase (ALT), lactate dehydrogenase (LDH), gamma-glutamyltransferase (GGT), bilirubin, and albumin. The interview included questions about alcohol consumption and body mass index (BMI; self-calculated height and weight). Heritability (proportion of the population variance attributable to genetic variation) was estimated using structural-equation analyses before and after correction for alcohol consumption and BMI.

RESULTS

Structural-equation analyses revealed a substantial heritability (35-61%) for the four biochemical liver function tests: ALT, GGT, LDH, and bilirubin. The remaining variation could be attributed to individuals' nonfamilial environments. Adjustment for alcohol consumption and BMI had no influence on the heritability for ALT, GGT, LDH, and bilirubin. For albumin, two models fit equally well before adjustment for alcohol and BMI: a model including additive genetic and nonshared environmental factors (AE), and a model including shared and nonshared environmental factors (CE). After adjustment, the model including shared and nonshared environment was clearly the best fitting model.

CONCLUSIONS

For both males and females, the effect of genetic factors on the biochemical liver function tests ALT, GGT, LDH, and bilirubin is substantial and accounts for one-third to two-thirds of the variation among individuals 73-102 years of age. The heritability is equal for males and females and does not change notably after controlling for alcohol consumption and BMI. For albumin, no major impact of genetic factors was found independent of BMI and alcohol consumption. An understanding of the genetic mechanisms underlying biochemical liver function tests among the very old may be of value in the interpretation of these tests in this age group.

DNA single strand break analysis in mononuclear blood cells of petrol pump attendants

DNA single strand breaks, including DNA adducts that lead to alkali-labile sites, were measured in peripheral mononuclear blood cells of 35 petrol pump attendants by alkaline filter elution. Blood samples from petrol pump attendants were taken on Monday and Friday. Additionally, DNA single strand breaks of smoking and non-smoking control persons were examined. For the smoking (n = 12) and the non-smoking controls (n = 20) a mean normalized elution rate of 1.49 +/- 0.52 (mean value +/- 95% confidence interval) and 1.32 +/- 0.28, respectively, was obtained. The difference between smoking and non-smoking controls was not statistically significant (U test). An increase in DNA single strand breaks from Monday to Friday was detected for non-smoking petrol pump attendants with a daily working time of more than 4 h at the pump station. Their mean normalized elution rate increased from 1.08 on Monday to 1.89 on Friday. This difference was statistically significant (P < 0.05; Wilcoxon test for paired data), although the 95% confidence interval was large on Friday (0.43 on Monday; 1.23 on Friday). However, no significant increase was found for non-smoking petrol pump attendants who were on duty for less than 4 h per day at the pump station. No statistically significant increase in DNA single strand breaks could be detected for smoking petrol pump attendants whether they were pumping gasoline for more or for less than 4 h per day.

Some problems of future demographic processes in China

"In this paper, which is based on a projection model of rural-urban population dynamics established by the authors, we make use of the investigative data of the one percent national population sample of 1987 and analog calculations on almost 200 demographic parameters to clarify the problematic relations between some key issues in China's future demographic processes. We advance a number of suggestions for the reference of policy-makers and planners."