Time trends in incidence of postpartum depression and depression in women of reproductive age.

BACKGROUND: Little is known about the time trends of postpartum depression (PPD) and whether they differ from time trends of depression among women in general. METHODS: Using Danish health registers, we identified a postpartum population from all women who had a liveborn child from 2000-2022. We sampled a background population by matching five women for each delivery on age and date of childbirth. Depression and PPD were measured as incident depression diagnosis or redeemed antidepressant prescription within 180 days from childbirth/matching. We described incidence rates from 2000-2022 using Poisson regression with a restricted cubic spline. RESULTS: The study population included 1,133,947 postpartum women (669,101 unique), matched to 5,669,735 women (1,165,505 unique). Overall IR per 10,000 person-years of diagnoses was 34.3 (95% CI: 32.8-35.9) for PPD and 18.9 (95% CI: 18.3-19.4) for depression. Both IRs increased similarly over time in the main analyses, but more pronounced for PPD in primiparous and older mothers. Correspondingly, IR for prescriptions was 135.7 (95% CI: 132.7-138.8) for PPD and 209.8 (95% CI: 208.1-211.5) for depression, and both groups had fluctuating time trends. LIMITATIONS: Depression measures were based on women who actively sought and received treatment, expectedly underestimating true disease incidence. CONCLUSIONS: Incidence rates of PPD and depression diagnoses increased over time, especially for PPD among primiparous and older mothers. These findings could suggest either increased vulnerability or increased awareness and detection over time in these groups. Fluctuating trends overserved from prescriptions could likely be driven by external factors and not a reflection of disease trends.

The HOPE cohort: cohort profile and evaluation of selection bias.

The HOPE cohort is a Danish nationwide cohort with ongoing follow-up, holding information on postpartum depression (PPD) symptoms and diagnoses on 170,218 childbirths (142,795 unique mothers). These data have been linked with extensive register data on health and socioeconomic information on the mothers, their partners, parents, and children. This cohort profile aimed to provide an overview of the data collection and content, describe characteristics, and evaluate potential selection bias. PPD screenings, using the Edinburgh Postnatal Depression Scale, were collected from 67 of the 98 Danish municipalities, covering the period January 2015 to December 2021. This data was linked with register data on PPD diagnoses (identified through medication prescriptions and hospital contacts) as well as background information. Cohort characteristics were compared to the source population, defined as all childbirths by women residing in Denmark during the same period (452,207 childbirths). Potential selection bias was evaluated by comparing odds ratios of five well-established associations between the cohort and the source population. The HOPE cohort holds information on 170,218 childbirths (38% of the source population) involving 142,795 unique mothers. The HOPE cohort only differed slightly from the source population on most characteristics examined, but larger differences were observed on specific characteristics with an underrepresentation of the youngest and oldest age groups, women with more than three children or twins/triplets, and women born outside Denmark. Similar associations were identified across the two populations within the five well-established associations. There was no indication of selection bias on the five examined associations, and the HOPE cohort is representative of the source population on important perinatal characteristics.

Is the sequence ratio an unbiased estimate of the incidence rate ratio? A simulation study.

PURPOSE: We aimed to evaluate the conditions under which the sequence ratio (SR) obtained from a sequence symmetry analysis is an unbiased estimate of the true incidence rate ratio (IRR). METHODS: We simulated cohorts of 1 million individuals who could initiate an exposure drug and experience a very rare, rare, common, or frequent outcome of interest. The outcome rate among exposed individuals was modified by a true incidence rate ratio of 0.2, 0.5, 1.0, 2.0, and 5.0. We further evaluated scenarios where the outcome was fatal and led to immediate censoring or the outcome reduced the rate of initiation of the exposure drug. RESULTS: We found the SR to be close to unbiased for rare, common, and frequent events, except when the true IRR was 5.0 (mean SR 4.94 and 3.74 for common and frequent events). The SR was slightly biased when the outcome was very rare. When the outcome was potentially fatal, the SR was increasingly biased with an increasing probability of death. Likewise, when the outcome reduced the probability of future exposure, the SR was upwards biased. CONCLUSION: The SR is a biased estimate of the incidence rate ratio, when the true IRR is high, the outcome has a high mortality, or when the outcome reduces the probability of future exposure.

Women's health literacy and attendance in breast cancer screening: a Danish population-based study combining survey and register data.

AIM: To investigate the association between women's health literacy and attendance in the Danish national breast cancer screening programme. METHODS: In a population-based cross-sectional study, information on two health literacy subscales, measured using the Health Literacy Questionnaire (HLQ), and sociodemographic factors was obtained from the 'How are you? 2017' survey in the Central Denmark Region. Information on screening attendance was obtained from register data from 2016-2017. Data were linked based on individual civil registration numbers. To account for missing data, multiple imputation by chained equations was implemented to fill in missing values on all variables. Unadjusted and adjusted logistic regression analyses were performed separately for two HLQ subscales to estimate odds ratio (OR) of screening attendance. Both multiple imputation analyses and complete case analyses were performed. RESULTS: A total of 6012 women were included in multiple imputed statistical analyses. Generally, women had high health literacy levels. In multiple imputed analyses, the unadjusted OR of the primary HLQ subscale, understanding, was 1.32 (95% confidence interval (CI): 1.10-1.59), indicating higher odds for screening attendance with higher health literacy level. However, after adjustment no significant association between the HLQ subscale of understanding and screening attendance was found (OR 1.09 (95% CI: 0.90-1.33)). Similar results were found for the secondary HLQ subscale of engaging (insignificant association in adjusted analysis). No effect modification from sociodemographic characteristics was found. Similar results were found in complete case analyses. CONCLUSIONS: No significant association was found between health literacy and attendance in the Danish breast cancer screening programme.