Key result
Higher pregnancy count is linked to a dose-dependent increase in incident AF risk.
Why the study?
Increased parity is associated with CVD risk, but its relationship with AF in women remained an open question.
Does an increased number of pregnancies increase the risk of incident atrial fibrillation in women?
Cohort (n=34,639)
Does an increased number of pregnancies increase the risk of incident atrial fibrillation in women?
p-value: p=0.004 for trend
In initially healthy women, an increasing number of pregnancies is independently associated with a higher risk of developing atrial fibrillation later in life.
Captured external expert commentary on this paper, strongest first. Original sources are linked where available.
“We found that an increase in the number of pregnancies was associated with a higher risk of future atrial fibrillation. For example, women with four or more pregnancies were approximately 30 percent to 50 percent more likely to develop atrial fibrillation compared to women with no pregnancies.”
“The authors describe a linear increase in AF with increasing number of children. This is interesting by itself and an explanation could be given by biological and sociocultural factors.”
“Little was known about the impact of pregnancy and its complications on subsequent cardiovascular disease in the offspring and mother. This inaugural issue is a new effort to address the menace of heart and vascular disease in women.”
Parity should not yet inform AF risk stratification in women; extends prior parity-CVD links but remains hypothesis-generating.
Increased parity is independently associated with risk of cardiovascular disease (CVD) in large observational studies. 1 Although CVD is a strong risk factor for the development of atrial fibrillation (AF), 2 little is known about the relationship between parity and AF risk.To address these gaps in knowledge, and given the significant impact AF has in women, we sought to examine the relationship between parity and AF in a large cohort of women free of CVD and AF at baseline within the WHS (Women's Health Study).WHS began as a randomized trial examining the use of aspirin versus placebo for the primary prevention of CVD and cancer.3 The study enrolled 39 876 women aged ≥45 years without CVD or any major illness.Development of prespecified health outcomes, and updated demographic, lifestyle, and CVD risk factor information were captured in annual questionnaires.The randomized trial was completed in March 2004, and subjects were invited to participate in observational follow-up.Women reported their number of pregnancies lasting at least 6 months in duration at baseline and incident AF events beginning at 48 months and annually thereafter.Medical records were sought for all self-reported incident AF cases, and events were adjudicated by a committee of cardiologists.Only AF events confirmed by medical record review were included in the analysis.Patients who self-reported AF (n=876), CVD (n=14), or an unknown number of pregnancies at baseline (n=137) were excluded.We also excluded 4210 women who did not participate in observational follow-up because AF could not be reliably confirmed.3 The study population thus consisted of 34 639 women.All participants provided written informed consent, and the study was approved by Brigham and Women's Hospital institutional review board.The number of pregnancies ≥6 months was grouped into 5 categories (0 [referent], 1, 2-3, 4-5, ≥6) adapted from Ness et al. 1 Multivariable, time-updated, Cox proportional-hazards models were used to estimate the association between number of pregnancies and incident AF.Tests for linear trend were performed by assigning the median value to each pregnancy category and modeling this as a continuous variable in separate Cox models.All models were constructed without imputation for missing data.Person-time was calculated from return of the baseline questionnaire to the date of incident AF, death, loss to follow-up, or December 31, 2014, whichever occurred first.Median baseline age was 52.9 years (interquartile range, 48.9-58.8),and median number of pregnancies was 2 (interquartile range, 2-3).During a median follow-up of 20.5 years, 1532 incident AF cases occurred.The Table summarizes multivariable-adjusted hazard ratios and 95% confidence intervals for incident AF according to the number of pregnancies.After adjusting for age, there was a linear increase in the hazard ratio for incident AF across increasing parity categories (P-trend=0.004).This relationship was strengthened after controlling for body mass index, diabetes mellitus, other AF and CVD risk factors,
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Wong et al. (2017) conducted a cohort in Healthy women (free of CVD and AF) (n=34,639). Increasing number of pregnancies ≥6 months vs. 0 pregnancies (nulliparous) was evaluated on Incident atrial fibrillation (p=0.004 for trend). Compared to nulliparous women, increasing number of pregnancies was associated with a linear increase in the risk of incident atrial fibrillation (p-trend=0.004).
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