What explains the link between reproductive events and women’s longevity?

Reproductive history and physical functioning in midlife: The Bogalusa Heart Study

OBJECTIVE

To examine the relationship between reproductive history, pregnancy complications, and later physical function.

STUDY DESIGN

The Bogalusa Heart Study is a long-running study of cardiovascular health in a semirural community. 761 women were interviewed about their pregnancy history and complications, and underwent tests of physical function. Logistic models for dichotomous outcomes and linear models for continuous outcomes were used, adjusted for covariates.

MAIN OUTCOME MEASURES

Overall scores on the Short Physical Performance Battery (SPPB), which combines scores for balance, gait speed, and chair stands. Additional tests were a 6-min walk, knee extension strength, grip strength, and a pegboard challenge.

RESULTS

Nulliparity was associated with lower scores on the walking and balance portions of the SPPB, less distance covered in the 6-min walk, less knee and grip strength, and higher pegboard time, especially among pre-menopausal women. A history of gestational diabetes was associated with more problems on the walk portion of the SPPB (aOR 2.44, 1.06-5.65), higher chair stand time, and lower knee strength. Young age at first birth (<16 or 18 years) was associated with a shorter chair stand time and a better pegboard score.

CONCLUSIONS

Nulliparity was associated with worse physical functioning, while high parity and early pregnancy were not, suggesting that fertility is associated with better health later in life. Pregnancy complications were associated with worse physical functioning, even after controlling for body mass index. Future studies should attempt to establish the pathways by which reproductive health relates to overall physical functioning.

Historical demography and longevity genetics: Back to the future

Research into the genetic component of human longevity can provide important insights in mechanisms that may protect against age-related diseases and multi-morbidity. Thus far only a limited number of robust longevity loci have been detected in either candidate or genome wide association studies. One of the issues in these genetic studies is the definition of the trait being either lifespan, including any age at death or longevity, i.e. survival above a diverse series of thresholds. Likewise heritability and segregation research have conflated lifespan with longevity. The heritability of lifespan estimated across most studies has been rather low. Environmental factors have not been sufficiently investigated and the total amount of genetic variance contributing to longevity has not been estimated in sufficiently well-defined and powered studies. Up to now, genetic longevity studies lack the required insights into the nature and size of the genetic component and the optimal strategies for meta-analysis and subject selection for Next Generation Sequencing efforts. Historical demographic data containing deep genealogical information may help in estimating the best definition and heritability for longevity, its transmission patterns in multi-generational datasets and may allow relevant additive and modifying environmental factors such as socio-economic status, geographical background, exposure to environmental effects, birth order, and number of children to be included. In this light historical demographic data may be very useful for identifying lineages in human populations that are worth investigating further by geneticists.

Maternal Age at Childbirth and Parity as Predictors of Longevity Among Women in the United States: The Women's Health Initiative

OBJECTIVES

To examine associations of maternal age at childbirth and parity with survival to age 90 years (longevity).

METHODS

We performed a prospective study among a multiethnic cohort of postmenopausal US women in the Women's Health Initiative recruited from 1993 to 1998 and followed through August 29, 2014. We adjusted associations with longevity for demographic, lifestyle, reproductive, and health-related characteristics.

RESULTS

Among 20 248 women (mean age at baseline, 74.6 years), 10 909 (54%) survived to age 90 years. The odds of longevity were significantly higher in women with later age at first childbirth (adjusted odds ratio = 1.11; 95% confidence interval = 1.02, 1.21 for age 25 years or older vs younger than 25 years; P for trend = .04). Among parous women, the relationship between parity and longevity was significant among White but not Black women. White women with 2 to 4 term pregnancies compared with 1 term pregnancy had higher odds of longevity.

CONCLUSIONS

Reproductive events were associated with longevity among women. Future studies are needed to determine whether factors such as socioeconomic status explain associations between reproductive events and longevity.