Perspectives on the Future of Epidemiology: A Framework for Training.

Over the past century, the field of epidemiology has evolved and adapted to changing public health needs. Challenges include newly emerging public health concerns across broad and diverse content areas, new methods, and vast data sources. We recognize the need to engage and educate the next generation of epidemiologists and prepare them to tackle these issues of the 21st century. In this commentary, we suggest a skeleton framework upon which departments of epidemiology should build their curriculum. We propose domains that include applied epidemiology, biological and social determinants of health, communication, creativity and ability to collaborate and lead, statistical methods, and study design. We believe all students should gain skills across these domains to tackle the challenges posed to us. The aim is to train smart thinkers, not technicians, to embrace challenges and move the expanding field of epidemiology forward.

Parental socioeconomic status and risk of cerebral palsy in the child: evidence from two Nordic population-based cohorts.

Background: We investigated whether the risk of cerebral palsy (CP) in the child varies by parents' socioeconomic status, in Denmark and Norway. Methods: We included almost 1.3 million children born in Demark during 1981-2007 and 2.4 million children born in Norway during 1967-2007, registered in the Medical Birth registries. Data on births were linked to Statistics Denmark and Norway to retrieve information on parents' education and relationship status and, in Denmark, also income. CP diagnoses were obtained from linkage with national registries. We used multivariate log-binominal regression models to estimate relative risk (RR) of CP according to parental socioeconomic status. Results: There was a strong trend of decreasing risk of CP with additional education of both the mother and the father. These trends were nearly identical for the two parents, with a one-third reduction in risk for those with the highest education compared with parents with the lowest education. When both parents had high education, risk of CP was further reduced (RR 0.58, 0.53-0.63). Women with partners had a reduction in risk (RR 0.79, 0.74-0.85) compared with single mothers overall. Risk patterns were stable over time, across countries and within spastic bilateral and unilateral CP. Household income was not associated with risk of CP. Conclusions: Risk of CP in two Scandinavian countries was lower among educated parents and mothers with a partner, but unrelated to income. Factors underlying this stable association with education are unknown, but could include differences in potentially modifiable lifestyle factors and health behaviours.

The economic and operational value of using drones to transport vaccines.

BACKGROUND: Immunization programs in low and middle income countries (LMICs) face numerous challenges in getting life-saving vaccines to the people who need them. As unmanned aerial vehicle (UAV) technology has progressed in recent years, potential use cases for UAVs have proliferated due to their ability to traverse difficult terrains, reduce labor, and replace fleets of vehicles that require costly maintenance. METHODS: Using a HERMES-generated simulation model, we performed sensitivity analyses to assess the impact of using an unmanned aerial system (UAS) for routine vaccine distribution under a range of circumstances reflecting variations in geography, population, road conditions, and vaccine schedules. We also identified the UAV payload and UAS costs necessary for a UAS to be favorable over a traditional multi-tiered land transport system (TMLTS). RESULTS: Implementing the UAS in the baseline scenario improved vaccine availability (96% versus 94%) and produced logistics cost savings of $0.08 per dose administered as compared to the TMLTS. The UAS maintained cost savings in all sensitivity analyses, ranging from $0.05 to $0.21 per dose administered. The minimum UAV payloads necessary to achieve cost savings over the TMLTS, for the various vaccine schedules and UAS costs and lifetimes tested, were substantially smaller (up to 0.40L) than the currently assumed UAV payload of 1.5L. Similarly, the maximum UAS costs that could achieve savings over the TMLTS were greater than the currently assumed costs under realistic flight conditions. CONCLUSION: Implementing a UAS could increase vaccine availability and decrease costs in a wide range of settings and circumstances if the drones are used frequently enough to overcome the capital costs of installing and maintaining the system. Our computational model showed that major drivers of costs savings from using UAS are road speed of traditional land vehicles, the number of people needing to be vaccinated, and the distance that needs to be traveled.

Association of Women's Reproductive History With Long-term Mortality and Effect of Socioeconomic Factors.

OBJECTIVE: To assess the effects of socioeconomic factors on the association between parity and long-term maternal mortality. METHODS: This was a population-based cohort study of mothers with births registered in the Medical Birth Registry of Norway during the period 1967-2009. We estimated age-specific (40-69 years) cardiovascular and noncardiovascular mortality ratios by number of births using Cox proportional hazard models. To assess effect modification by mothers' attained education, we stratified on low (less than 11 years) and high (11 years or greater) educational level. We further evaluated fathers' mortality by number of births using the same analytical approach. RESULTS: Mothers with low education had higher mortality (cardiovascular: hazard ratio 2.62, 95% confidence interval [CI] 2.34-2.93, noncardiovascular: hazard ratio 1.67, 95% CI 1.62-1.73). Among mothers with low education, cardiovascular mortality increased linearly with each additional birth above one (P trend=.02). In contrast, among mothers with high education, cardiovascular mortality declined with added births (P trend=.045). For noncardiovascular mortality there was no association among mothers with low education, whereas mortality declined with increasing number of births among mothers with high education (P trend<.01). Father's mortality showed similar associations with number of births when stratified on maternal education. CONCLUSION: Women's long-term mortality rose with number of births only for cardiovascular causes of death and only among mothers with low education. Partners of women with low education had similar increasing risk with increasing number of births. Maternal educational level is a strong modifier of the association between parity and long-term mortality. LEVEL OF EVIDENCE: II.

Benchmark pregnancy rates and the assessment of post-coital contraceptives: an update.

OBJECTIVE: In 2001, we provided benchmark estimates of probability of pregnancy given a single act of intercourse. Those calculations assumed that intercourse and ovulation are independent. Subsequent research has shown that this assumption is not valid. We provide here an update of previous benchmark estimates. STUDY DESIGN: We reanalyze earlier data from two North Carolina studies that collected daily urine samples and recorded daily intercourse for multiple menstrual cycles. One study comprised 68 sexually active women with either an intrauterine device or tubal ligation. The second was of 221 women who planned to become pregnant and had discontinued use of any birth control at enrollment. Participants had no known fertility problems. New statistical analyses were based on Monte Carlo simulations and Bayesian methods. RESULTS: The probability that a single act of intercourse occurs within a woman's fertile window is 25%, compared with 20% in previous calculations. The probability of pregnancy with intercourse on a given menstrual cycle day is correspondingly higher than previously estimated, with the largest increases occurring on menstrual days 12-22. These increases are, however, fairly small (for example, the peak chance of conception on menstrual day 13 increased from 8.6% to 9.7%). CONCLUSIONS: Previous benchmark rates of pregnancy with one act of intercourse were moderately underestimated due to a mistaken assumption about the independence of intercourse and ovulation. IMPLICATIONS STATEMENT: The chance of pregnancy with a single act of unprotected intercourse is greater than previously estimated. Previous benchmarks may underestimate the efficacy of post-coital contraception.

Invited commentary: Natural versus unnatural sex ratios--a quandary of modern times.

The typical dilemma with sex-ratio findings is that when they are real, they aren't interesting, and when they are interesting, they aren't real. In this issue of the Journal, Fernández et al. (Am J Epidemiol. 2011;174(12):1327-1331) describe a deviation of the sex ratio that is apparently both large and real. There was a temporary but distinct spike in the proportion of boys born in Cuba around the time of the collapse of the national economy during the 1990s. Although an excess of boys does not fit the prevailing biologic theory regarding maternal stress and the sex ratio, the data are consistent with results from the Dutch famine (where population-level deprivation was even more extreme). A new quandary arises in the modern era with interpretation of the sex ratio: If the decision to abort a pregnancy is influenced by the sex of the fetus, a change in the behavior of even a small proportion of women could influence the sex ratio at birth. The possible role of sex selection in the Cuban context is discussed.

The use of epidemiological evidence in the compensation of veterans.

Men and women serving in the U.S. military are exposed to diverse agents that may affect their health, causing injury and disease while they are in the service or after discharge. This case study addresses the compensation of veterans for injury and illnesses arising from exposures received during military service and focuses on the presumptions that are made around compensation of veterans for conditions arising after their service. Presumptions are made because of evidence gaps related to exposure and causation. The current process for evidence review related to causation involves Institute of Medicine (IOM) committees that evaluate evidence relevant to association. The Veterans Administration uses the IOM reports in making presumptions. A new approach was recommended by an IOM committee: a transparent, evidence-based approach that would lead to decisions by means of an explicit process. The Committee set out six principles as a foundation for its framework: stakeholder inclusiveness, evidence-based decisions, transparent process, flexibility, consistency, and the use of causation, not just association, as the basis for decision making. The committee also called for needed tracking of exposure and associated health outcomes during and after military service. This case study covers "lessons learned" around evidence synthesis, causal inferences, and decision-making.

Completeness of registration of oral clefts in a medical birth registry: a population-based study.

BACKGROUND: Epidemiological surveillance and research on birth defects require accurate diagnosis and adequate registration. In this regard, the performance of national birth registries is not well described. METHODS: We linked clinical data from all 3,616 cleft cases treated in Norway between 1967 and 1998 with data from the Medical Birth Registry of Norway, and calculated the proportion of clinically verified cases reported to the Registry, stratified by severity. RESULTS: The cleft type most completely ascertained was cleft lip and palate (CLP), of which 94% were reported. Ascertainment was less complete for cleft lip alone (83% recorded), and cleft palate only (CPO) (57% recorded). For each of the three types of clefts, completeness of reporting depended on severity of the cleft. For example, 71% of cases with severe CPO were reported, while only 11% of cases with mild CPO were reported. CONCLUSIONS: Ascertainment was strongly related to cleft type and severity. To the degree that severity of birth defects may be related to their cause, these patterns of registration have implications for surveillance of birth defects as well as the conduct of etiologic studies. The large proportion of cleft palate cases unrecorded at birth suggests that clinical examination of the newborn palate is often inadequate.