שנת סיום: 2023

כותרת עבודת הדוקטורט: Biological aging and social interaction: The role of positive and negative social interactions in telomere length, among postpartum mothers in Northern Israel

מנחים: פרופ' אורנה בראון- אפל וד"ר שירן בורד

Abstract

Women's reproduction requires increased energy demands, which consequently may lead to cellular damage and aging. Moreover, beyond the physical and psychological stressors endured during pregnancy and childbirth, postpartum women are susceptible to physical and psychological stressors as they navigate recovery from childbirth and adjust to their new role as a parent. Overall, psychosocial stressors are linked with declined physical and psychological health, and short telomere length (TL) - the protective "caps" at the end of chromosomes which serve as biomarkers for cellular aging.

Social interactions a major potential psychosocial stressor is crucial for mothers’ wellbeing postpartum. Social support postpartum is associated with mothers’ improved health and faster recovery after birth. Nonetheless, the quality of social interactions determines its effect on health as positive social relationships are associated with better health and longer telomeres, whereas negative social interactions are associated with declined health and shorter telomeres, and this is especially prominent in women. Adding to that, transitioning to motherhood can create work family conflicts, since returning to work postpartum encapsules potential stressors that have yet been thoroughly studied in terms of their effect on mothers’ health and TL. Although employment is generally associated with longer telomeres, this association may diminish during the early years of child-rearing.

Limited research examined the longitudinal effects of psychosocial stressors and telomere dynamics postpartum. Given the significant physical and emotional symptoms experienced by women during the postpartum period, recognizing potential postpartum stressors and understanding their effect on women’s health is crucial. Thus, the aim of this PhD dissertation was to first review reproductive related stressors systematically on women’s health and TL, including telomere dynamics throughout pregnancy and the association between parity and TL overtime. And second, assess postpartum psychosocial stressors including the effect of positive and negative social interactions as well as the impact of work re-entry on TL among first-time mothers, throughout the first year postpartum.

Methods

The research framework included two phases. First a systematic search was conducted across seven databases including CINAHL, Cochrane, PsycINFO, Proquest, PubMed; Scopus; and Web of Science, using keywords and MeSH descriptors of pregnancy, parity, and TL. Predefined  inclusion and exclusion criteria were used to screen abstracts and titles which yielded14  studies that were included in the final review to assess the effect of pregnancy on TL and the association between parity and TL. A mini meta‑analysis utilized JASP 0.17.3 software and included 4 applicable studies, comprising a total of 2564 participants to quantitatively assess the estimated effect size of parity on TL.

Second, 103 first-time mothers were recruited in a cohort study from Northern Israel. Data collection took place during two periods, first, between November 2020 and June 2021 – within one month postpartum, and second, between November 2021 and June 2022 – one year postpartum. At each timepoint mothers provided dried blood spots to measure TL and completed questionnaires with validated measures of positive and negative social support, marital satisfaction, current working status, depressive symptoms, physical activity and other health related behaviors, perceived stress and demographic data. Logistic and linear regressions assessed whether various psychosocial stressors such as social interactions and one-year postpartum working status predicted change in TL at the end of the one year follow up.

Main Findings

Findings from the systematic review revealed, out of the 11 studies reviewed on parity and TL, four demonstrated a negative correlation; one – a positive correlation and six -found no correlation. Studies demonstrating a negative correlation encompassed rigorous methodological practices possibly suggesting having more children is correlated with enhanced telomere The mini meta‑analysis revealed a negative, yet, non‑significant effect, of the estimated effect size of parity on TL(ES = ‑0.009,p = 0.126, CI ‑0.021, 0.03). Of the four longitudinal studies assessing telomere dynamics throughout pregnancy, most found no change in TL from early pregnancy to postpartum suggesting pregnancy does not affect TL from early pregnancy to early postpartum.

Telomere dynamics throughout the one year follow up which was calculated by a paired two tailed sample t test between TL at timepoint 2 (M=1.60,  SD=0.22) and timepoint 1 (M=1.52, SD=0.20) demonstrated a significant increase in TL  )M= .08 , SD=0.134, t(6.057) , p = .000). We observed telomere shortening, moderate telomere lengthening and relatively high telomere lengthening in the lower, medium, and upper tertiles of change in telomere length, respectively. 

Logistic regressions analyses revealed mothers who reported a higher level of marital satisfaction {Marital Satisfaction OR=3.617, CI (1.278, 10.248) p=.016}.  and a lower level, or no negative social interactions {OR=.289, (CI .096, .868) p=.027},  had a three-fold higher likelihood of belonging to the upper tertile of positive change in telomere length. A negative COVID19 diagnosis was associated with a three-fold increase in the odds of belonging to the positive upper tertile of change  in telomere length at timepoint 2 {OR = 3.264; 95% CI 1.231-8.659), p = 0.017} . Moreover, we found that working status significantly predicted change in TL and was negatively correlated with change in TL over time ( β = − 0.245, 95% CI -0.169, -0.018, p = 0.016). 

Research Contributions

Despite the common practice of monitoring prenatal health, postpartum mothers often lack sufficient follow-up, leaving them unsupported despite facing various physical and psychological challenges that extend beyond the initial six-week follow up period. Due to the importance of telomere function in cellular health and longevity early recognition of stressors impacting postpartum mothers is crucial. This study emphasizes the potential impact of multiple pregnancies on mothers' health and longevity and emphasizes the need to identify and treat modifiable psychosocial stressors postpartum.

Limited research exists on the effect of social interactions on TL, particularly among postpartum women. Moreover, this longitudinal study explores the type and source of social support, highlighting the significant role of spouse support on postpartum mothers’ health and TL as well as the magnitude by which social negativity affects postpartum mothers’ TL.

This study establishes the basis for intervention programs and early screening tests for postpartum women by elucidating the mechanism by which stressful social encounters affect health. Understanding the impact of positive family support, especially spouse support, and negative social interactions on health and TL aids in diagnosing and customizing support for postpartum women, facilitating their recovery. Moreover, it emphasizes the adverse effects of untimely work re-entry for first-time mothers on mental and physical health, as well as telomere dynamics, underscoring the need for further research on optimal timing of work re-entry that considers individual needs, preferences, and occupational factors.Top of Form

Conclusions

Reproduction is a complex biological process with implications for women's health. The effect of pregnancy on TL including the effect of multiple pregnancies on women’s health and TL overtime requires further investigation. Various additional postpartum stressors can significantly impact women's health and TL, nonetheless, identifying and focusing on modifiable stressors is essential to improve mothers’ health and minimize their effect on TL. Modifiable psychosocial stressors, which have been found to negatively impact TL in this study include negative social interactions, lack of spousal support and employment status at one year postpartum.

Recognizing that new mothers' needs extend beyond the traditional six-week recovery period is essential. Postpartum screening tests should consider assessing social interactions, moreover, designing programs to support and guide mothers in reducing stress, balancing work and family life, and addressing and encouraging proper social support can improve postpartum health outcomes. Considering policy changes regarding maternity leave length are also recommended.

In conclusion, this study highlights the importance of addressing the challenges faced by new mothers and calls for additional research to explore the relationship between social interactions and health and identify ideal timing of work re-entry through telomere dynamics especially among first-time postpartum mothers.

Practical implications for future research

Studies assessing the relationship between pregnancy and TL, and parity and TL have yielded mixed results necessitating further research to better understand the dynamics of pregnancy on TL and the effects of parity on TL over time. It is essential to clearly define parity and compare different age groups of women before and after menopause. These groups exhibit distinct hormone profiles and are exposed to different stressors over time, all of which can potentially impact TL. Furthermore, investigating telomerase levels can shed light on the link between pregnancy, parity, and TL since elevated estrogen levels during pregnancy have been linked to increased telomerase activity, which in turn facilitates the elongation of telomeres.

Social support is recognized as a key potential psychosocial stressor among women. Further studies should differentiate between the type of social support (positive or negative) and the subscales of positive and negative social interactions. Our study findings have shown significant correlations between TL and the conflict and insensitivity subscales of negative social interactions, triggering the need to determine whether specific aspects of social negativity exert more pronounced effects on health and TL. Assessing the impact of the source of social support (spouse, mother's family, spouse's family, friends, neighbors, acquaintances) in future studies is recommended as our study revealed positive associations between change in TL and spouse support mounting on findings of previous studies. Moreover, although no differences were found in our study between Arab and Jewish women in terms of social support and TL, further larger scale studies are recommended for a better understanding of the diverse social support needs mothers may have from different backgrounds. Finally, further research should focus on the effect of different postpartum maternal leave lengths from work, including different occupations and their effect on mothers’ and infants’ health and TL.