Birth month, birth season, and overall and cardiovascular disease mortality in US women: prospective cohort study

Associations between long-term aircraft noise exposure, cardiovascular disease, and mortality in US cohorts of female nurses

There is limited research examining aircraft noise and cardiovascular disease (CVD) risk. The objective of this study was to investigate associations of aircraft noise with CVD among two US cohorts, the Nurses' Health Study (NHS) and Nurses' Health Study II (NHSII).

Methods

Between 1994 and 2014, we followed 57,306 NHS and 60,058 NHSII participants surrounding 90 airports. Aircraft noise was modeled above 44 A-weighted decibels (dB(A)) and linked to geocoded addresses. Based on exposure distributions, we dichotomized exposures at 50 dB(A) and tested sensitivity of this cut-point by analyzing aircraft noise as categories (<45, 45-49, 50-54, ≥55) and continuously. We fit cohort-specific Cox proportional hazards models to estimate relationships between time-varying day-night average sound level (DNL) and CVD incidence and CVD and all-cause mortality, adjusting for fixed and time-varying individual- and area-level covariates. Results were pooled using random effects meta-analysis.

Results

Over 20 years of follow-up, there were 4529 CVD cases and 14,930 deaths. Approximately 7% (n = 317) of CVD cases were exposed to DNL ≥50 dB(A). In pooled analyses comparing ≥50 with <50 dB(A), the adjusted hazard ratio for CVD incidence was 1.00 (95% confidence interval: 0.89, 1.12). The corresponding adjusted hazard ratio for all-cause mortality was 1.02 (95% confidence interval: 0.96, 1.09). Patterns were similar for CVD mortality in NHS yet underpowered.

Conclusions

Among participants in the NHS and NHSII prospective cohorts who generally experience low exposure to aircraft noise, we did not find adverse associations of aircraft noise with CVD incidence, CVD mortality, or all-cause mortality.

Education mediating the associations between early life factors and frailty: a cross-sectional study of the UK Biobank

OBJECTIVES

Exposures in utero and during infancy may impact the development of diseases later in life. They may be linked with development of frailty, although the mechanism is unclear. This study aims to determine the associations between early life risk factors and development of frailty among middle-aged and older adults as well as potential pathways via education, for any observed association.

DESIGN

A cross-sectional study.

SETTINGS

This study used data from UK Biobank, a large population-based cohort.

PARTICIPANTS

502 489 individuals aged 37-73 years were included in the analysis.

PRIMARY AND SECONDARY OUTCOME MEASURES

Early life factors in this study included being breast fed as a baby, maternal smoking, birth weight, the presence of perinatal diseases, birth month and birth place (in or outside the UK). We developed a frailty index comprising 49 deficits. We used generalised structural equation modelling to examine the associations between early life factors and development of frailty and whether any observed association was mediated via educational attainment.

RESULTS

A history of breast feeding and normal birth weight were associated with a lower frailty index while maternal smoking, the occurrence of perinatal diseases and birth month with a longer day length were associated with a higher frailty index. Educational level mediated the relationship between these early life factors and frailty index.

CONCLUSIONS

This study highlights that biological and social risk occurring at different stages of life are related to the variations in frailty index in later life and suggests opportunities for prevention across the life course.

Season of Birth and Cardiovascular Mortality in Atrial Fibrillation: A Population-Based Cohort Study

Background: The fetal origins hypothesis have associated early life exposures with the development of adverse health outcomes in adulthood. Season of birth has been shown to be associated with overall and cardiovascular mortality. Methods: We performed a retrospective database study to explore the association between season of birth and mortality in patients with atrial fibrillation. Results: A total of 8962 patients with AF were identified in the database with 1253 deaths recorded. AF patients born in spring and summer had a higher mortality rate when compared to those born in autumn and winter (hazard ratio (HR) 1.13, 95% confidence interval (CI) 1.01–1.26, p = 0.03). This effect was consistent in the male subgroup (HR 1.25, 95% CI 1.03–1.51, p = 0.02 for males born in spring; HR 1.24, 95% CI 1.03–1.51, p = 0.03 for males born in summer when compared to winter as the reference) but not in females (HR 1.02, 95% CI 0.79–1.31, p = 0.88 for females born in spring; HR 1.11, 95% CI 0.87–1.42, p = 0.39 for females born in summer when compared to winter as the reference). Results persisted after adjustment for baseline characteristics and clinical risk profile. A similar pattern was observed with cardiovascular mortality. Conclusion: Birth in spring or summer is associated with a higher risk of cardiovascular mortality in male AF patients, but not in females. This could be related to the underlying differences in rates of major adverse clinical events between genders. Further studies should aim at clarifying the mechanisms behind this association, which may help us understand the higher level of risk in female patients with AF.

Impact of birth season on the years of life lost from respiratory diseases in the elderly related to ambient PM2.5 exposure in Ningbo, China

Background

Ambient fine particle (PM_2.5) pollution is an important public health problem in China. Short-term ambient PM_2.5 exposure is associated with increased mortality of respiratory diseases. However, few evidence was available on the effect of exposure to ambient PM_2.5 on the years of life lost (YLL) from respiratory diseases in the elderly. Furthermore, birth season which is frequently applied as a proxy for environmental exposure in early life may influence the health outcome in the later life. Nevertheless, the modification effect of birth season on the relationship of PM_2.5 exposure and respiratory health need to be explored.

Methods

A time-stratified case-crossover design was used to analyze YLL from respiratory diseases in the elderly related to ambient PM_2.5 exposure between 2013 and 2016 in Ningbo, China. The modification effect of birth season was explored by subgroup comparisons between different birth seasons.

Results

Each 10 μg/m³ increase in daily ambient PM_2.5 was associated with an increment of 1.61 (95% CI 0.12, 3.10) years in YLL from respiratory diseases in the elderly population. Individuals who were born in winter had significantly higher YLL from respiratory diseases associated with ambient PM_2.5 exposure than those who were born in other seasons.

Conclusions

Birth season which reflects the early-life PM_2.5 exposure level that may influence the lung development has a potential effect on the disease burden of respiratory diseases related to ambient PM_2.5 exposure in later life. The results would provide theoretical basis to protect vulnerable population defined by birth season when exploring the adverse effects of ambient PM_2.5 in the respiratory health.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12199-021-00994-6.

Birth month and mortality in Japan: a population-based prospective cohort study

Epidemiologic studies investigating the association between birth season and risk of mortality in adulthood are limited and have yielded inconclusive results. We aimed to examine the relationship between birth month and all-cause and cause-specific mortality, after controlling for potential confounders, including lifestyle and medical factors, in a population-based cohort study in Japan. We included 28,884 subjects (13,262 men and 15,622 women) from Takayama City, aged 35 years or older without cancer, stroke, and ischemic heart disease, who were born in Japan at baseline. Participants who were enrolled in 1992 were followed up for over 16 years. Information including place of birth, lifestyles, and medical history was obtained from a baseline questionnaire. We performed a Cox proportional hazards analysis to determine the association between birth month and all-cause and cause-specific mortality after adjusting for potential confounders. During the follow-up period (mean follow-up: 14.1 years), 5,303 deaths (2,881 men and 2,422 women) were identified. After controlling for multiple covariates, it was found that being born in April or June was associated with an increased risk of all-cause mortality compared to being born in January (hazard ratio [HR] 1.138; 95% confidence interval [CI], 1.006-1.288 and HR 1.169; 95% CI, 1.028-1.329, respectively). The HRs for cardiovascular mortality were significantly higher in participants born in March and May (HR 1.285; 95% CI, 1.056-1.565 and HR 1.293; 95% CI, 1.040-1.608, respectively). Our findings indicate that an individual's birth month may be an indicator of the susceptibility to mortality in later life.

Born in winter or spring more susceptible to all-cause and cardiovascular disease death in rural areas of China: results from a 11.9-year follow-up study

There has been no evidence on the effects of birth season and birth month on mortality in China. We aimed to explore the association between birth season, birth month and all-cause and cardiovascular disease (CVD) death. A population-based sample of 21,338 Chinese rural participants aged ≥35 years at baseline was included in our analysis. Age and multivariable adjusted Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the relationship between astronomical birth season (autumn as the reference), birth month (November as the reference), and all-cause and CVD mortality. During a median follow-up period of 11.9 years, 2,207 people died from all-cause and 1,214 people were attributed to CVD death. In multivariable adjusted analyses, for all-cause death, spring and winter had HRs (95% CIs) of 1.134 (1.005–1.280) and 1.162 (1.038–1.301), respectively; January, March, May, and August had HRs (95% CIs) of 1.249 (1.027–1.518), 1.234 (1.008–1.512), 1.276 (1.037–1.571), and 1.232 (1.003–1.513), respectively. For CVD death, spring and winter with HRs (95% CIs) of mortality were 1.232 (1.048–1.449) and 1.174 (1.007–1.369), respectively; March with HR (95% CI) of mortality were 1.343 (1.030–1.750) (all P < 0.05). Our study indicated that people born in the winter or spring were significantly associated with all-cause and cardiovascular disease mortality in rural areas of China.

Season-of-birth phenomenon in health and longevity: epidemiologic evidence and mechanistic considerations

In many human populations, especially those living in regions with pronounced climatic differences between seasons, the most sensitive (prenatal and neonatal) developmental stages occur in contrasting conditions depending on the season of conception. The difference in prenatal and postnatal environments may be a factor significantly affecting human development and risk for later life chronic diseases. Factors potentially contributing to this kind of developmental programming include nutrition, outdoor temperature, infectious exposures, duration of sunlight, vitamin D synthesis, etc. Month of birth is commonly used as a proxy for exposures which vary seasonally around the perinatal period. Season-of-birth patterns have been identified for many chronic health outcomes. In this review, the research evidence for the seasonality of birth in adult-life disorders is provided and potential mechanisms underlying the phenomenon of early life seasonal programming of chronic disease and longevity are discussed.

The influence of birth month on total and cardiovascular mortality: a population-based surveillance study

There is little evidence about the impact of birth month on total and cardiovascular disease mortality in developing countries. We evaluated these associations using the population health registration data of Hefei City, China from 2014 to 2017. After controlling for the fixed effects of gender, education, and occupation, we fitted the Cox proportional hazard regression model to assess the relationship between birth month and mortality. Hazard ratio (HR) with corresponding 95% confidence interval (CI) was calculated. All data analyses were performed by R 3.6.0 software. The data of 44 665 participants were analyzed in the study. Compared to people born in January, people born between May and October had higher total and cardiovascular mortality, being highest in June, respectively, HR: 1.130 (95%CI: 1.074 to 1.190) and HR: 1.200 (95%CI: 1.115 to 1.290). After stratification by gender, males born in June had highest risk total and cardiovascular mortality, with an increase in risk of 14.8% and 24.7%, respectively. For females, highest risk of total mortality was increased by 11.1% in those born in July, while those born in December had highest increase in cardiovascular mortality risk by 15.7%. Our results indicate in Hefei City, China month of birth is associated with total and cardiovascular disease mortality.