Time-varying Risk Factors Research Articles

Epidemiology of Suicide Attempts among Youth Transitioning to Adulthood.

Suicide is the second leading cause of death for older adolescents and young adults. Although empirical literature has identified important risk factors of suicidal behavior, it is less understood if changes in risk factors correspond with changes in suicide risk. To address this knowledge gap, we assessed if there were different trajectories of suicidal behavior as youth transition into young adulthood and determined what time-varying risk factors predicted these trajectories. This study used four waves of data spanning approximately 13 years from the National Longitudinal Study of Adolescent Health. The sample included 9027 respondents who were 12-18 years old (M = 15.26; SD = 1.76) at Wave 1, 50% male, 17% Hispanic, and 58% White. The results indicated that 93.6% of the sample had a low likelihood for suicide attempts across time, 5.1% had an elevated likelihood of attempting suicide in adolescence but not young adulthood, and 1.3% had an elevated likelihood of attempting suicide during adolescence and adulthood. The likelihood of a suicide attempt corresponded with changes on depression, impulsivity, delinquency, alcohol problems, family and friend suicide history, and experience with partner violence. Determining how suicide risk changes as youth transition into young adulthood and what factors predict these changes can help prevent suicide. Interventions targeting these risk factors could lead to reductions in suicide attempts.

Abstract P286: Egg Consumption is Associated With Cardiovascular Disease Risk Factors in the Coronary Artery Risk Development in Young Adults Study

Objective: The role of eggs in cardiovascular disease risk remains uncertain. Studies implicate a metabolite of choline , trimethylamine N-oxide (TMAO), in the development of cardiovascular disease (CVD). We tested the association between egg consumption and CVD risk factors over 20 years of follow-up. Methods: Study participants were from the CARDIA Study, a multicenter cohort of black and white Americans established in 1985/86 (baseline n=5,115; ages 18-30). Egg consumption was calculated from reported intake on a diet history at baseline and years 7 and 20 of follow-up. Eggs were categorized as: ≤1.0, 1.1-3.5, 3.6-6.9, and ≥7 per week. CVD risk factors were assessed at each exam, including blood pressure, lipids, and insulin resistance (defined by homeostatic model assessment, HOMA-IR). Multivariable-adjusted fixed effects (within-subject) regression models quantified prospective associations between time-varying egg consumption and CVD risk factors. Results: In the regression (Table), 7+ eggs per week was negatively associated with systolic and diastolic blood pressure and >3.5 eggs per week was positively associated with HDL-C. Total cholesterol and LDL-C were positively associated with low-to-moderate consumption, but not with higher consumption. Conclusion: At higher levels of intake, eggs were negatively associated with blood pressure and positively associated with HDL-C; at low-to-moderate levels, eggs were positively associated with total cholesterol and LDL-C. P

Acute Otitis Media During Infancy: Parent-reported Incidence and Modifiable Risk Factors.

Age at exposure to acute otitis media (AOM) risk factors such as day care attendance, lack of breastfeeding and tobacco smoke is little studied but important for targeting AOM prevention strategies. Moreover, studies are typically restricted to clinically diagnosed AOM, while a significant subset can occur outside the health care system, depending on the country setting. This study aims to determine risk factor exposure and effect of its timing within the first year of life on parent-reported AOM symptom episodes. In the WHeezing and Illnesses STudy LEidsche Rijn birth-cohort study, 1056 children were prospectively followed during their first year of life. Group day care attendance, breastfeeding and tobacco smoke exposure were recorded monthly and parent-reported AOM symptoms daily. Generalized estimating equations were used to estimate the association between the time-varying risk factors and AOM symptom episodes, while correcting for confounding by indication. The first-year incidence rate of parent-reported AOM was 569/1000 child-years [95% confidence interval (CI): 523-618]. Children who attended day care had higher odds of developing AOM symptom episodes compared with those not attending (odds ratio: 5.0; 95% CI: 2.6-9.6). Tobacco smoke exposure and (a history of) breastfeeding were not associated with AOM. Test for interaction revealed that the effect of day care increased with each month younger in age. First-year day care attendance is a major risk factor for AOM symptom episodes among infants in the community. This adjusted effect estimate is higher than previously reported and is age-dependent. AOM prevention strategies in day care facilities should therefore focus in particular on the youngest age groups.

‘Whatever It Takes’ to Resolve the European Sovereign Debt Crisis? Bond Pricing Regime Switches and Monetary Policy Effects

This paper investigates the role of unconventional monetary policy as a source of time-variation in the relationship between sovereign bond yield spreads and their fundamental determinants. We use a two-step empirical approach. First, we apply a time-varying parameter panel modelling framework to determine shifts in the pricing regime characterising sovereign bond markets in the euro area over the period January 1999 to July 2016. Second, we estimate the impact of ECB policy interventions on the time-varying risk factor sensitivities of spreads. Our results provide evidence of a new bond-pricing regime following the announcement of the Outright Monetary Transactions (OMT) programme in August 2012. This regime is characterised by a weakened link between spreads and fundamentals, but with higher spreads relative to the pre-crisis period and residual redenomination risk. We also find that unconventional monetary policy measures affect the pricing of sovereign risk not only directly, but also indirectly through changes in banking risk. Overall, the actions of the ECB have operated as catalysts for reversing the dynamics of the European sovereign debt crisis.

Self-Reported Arrests Among Indigenous Adolescents: a Longitudinal Analysis of Community, Family, and Individual Risk Factors.

North American indigenous (American Indian/Canadian First Nations) adolescents are overrepresented in the juvenile justice systems in the USA and Canada. One explanation advanced for disproportionate numbers of racial and ethnic minorities in the justice systems is the unequal distribution of risk factors across groups. The purpose of this study is to investigate the prevalence of and risk factors for first arrest within a population sample of indigenous adolescents. The data come from an 8-year longitudinal panel study of indigenous youth (n = 641) from the northern Midwest and Canada, spanning ages 10 to 19 years. We used a discrete-time survival model to estimate the overall hazard of first arrest and change in the arrest hazard over time and included both time-invariant and time varying risk factors. The risk of arrest increased over time, although the largest increase occurred between waves 3 and 4, when the adolescents averaged 13.1 and 14.3 years, respectively. The youth had a 55 % probability of being arrested at least once by the end of the study. Of the time-invariant risk factors, exposure to violence, parent arrest, age, and income were associated with overall risk of first arrest. Three time-varying risk factors (alcohol use, marijuana use, and peer delinquency) were associated with changes in the risk of first arrest. Being arrested carries significant repercussions for young people, including involvement in the juvenile justice system as well as consequences into adulthood. Communities must go beyond programs that target problem behaviors because community, family, and peer factors are also important.

Time-varying associations of suicide with deployments, mental health conditions, and stressful life events among current and former US military personnel: a retrospective multivariate analysis

US military suicides have increased substantially over the past decade and currently account for almost 20% of all military deaths. We investigated the associations of a comprehensive set of time-varying risk factors with suicides among current and former military service members. We did a retrospective multivariate analysis of all US military personnel between 2001 and 2011 (n=110 035 573 person-quarter-years, representing 3 795 823 service members). Outcome was death by suicide, either during service or post-separation. We used Cox proportional hazard models at the person-quarter level to examine associations of deployment, mental disorders, history of unlawful activity, stressful life events, and other demographic and service factors with death by suicide. The strongest predictors of death by suicide were current and past diagnoses of self-inflicted injuries, major depression, bipolar disorder, substance use disorder, and other mental health conditions (compared with service members with no history of diagnoses, the hazard ratio [HR] ranged from 1·4 [95% CI 1·14-1·72] to 8·34 [6·71-10·37]). Compared with service members who were never deployed, hazard rates of suicide (which represent the probability of death by suicide in a specific quarter given that the individual was alive in the previous quarter) were lower among the currently deployed (HR 0·50, 95% CI 0·40-0·61) but significantly higher in the quarters following first deployment (HR 1·51 [1·17-1·96] if deployed in the previous three quarters; 1·14 [1·06-1·23] if deployed four or more quarters ago). The hazard rate of suicide increased within the first year of separation from the military (HR 2·49, 95% CI 2·12-2·91), and remained high for those who had separated from the military 6 or more years ago (HR 1·63, 1·45-1·82). The increased hazard rate of death by suicide for military personnel varies by time since exposure to deployment, mental health diagnoses, and other stressful life events. Continued monitoring is especially needed for these high-risk individuals. Additional information should be gathered to address the persistently raised risk of suicide among service members after separation. Partly funded by the Naval Research Program.

Time-varying risk, mispricing attributes, and the accrual premium

We examine the mispricing attributes of the accrual effect in the presence of time-varying common risk factors, which are not independent of aggregate economic conditions. We find that the persistence of unconditional abnormal returns for accrual-based portfolios is not independent of firm-level characteristics such as size and book-to-market ratio (BE/ME). However, after adjusting for time-varying risk measures, the premiums associated with accruals and firm fundamentals are distinct from one another. The empirical evidence shows that a long-short hedge portfolio based on accruals and BE/ME generates significant abnormal returns even in the presence of time-varying risk. Taken together, our time-series and cross-sectional evidence strengthens the assertion that the well-known accrual effect is significantly associated with high-BE/ME value firms that tend to be low-investment firms. The fact that time-varying risk adds to the description of average returns of accrual-sorted portfolios and corroborates the presence of the accrual premium contributes significantly to the literature.

“What’s the Risk?” Assessing and Mitigating Risk in Cardiothoracic Surgery

“What’s the Risk?” Assessing and Mitigating Risk in Cardiothoracic Surgery

Physical and Sexual Violence Predictors: 20 Years of the Women's Interagency HIV Study Cohort.

Gender-based violence (GBV) threatens women's health and safety. Few prospective studies examine physical and sexual violence predictors. Baseline/index GBV history and polyvictimization (intimate partner violence, non-partner sexual assault, and childhood sexual abuse) were characterized. Predictors of physical and sexual violence were evaluated over follow-up. HIV-infected and uninfected participants (n=2,838) in the Women's Interagency HIV Study provided GBV history; 2,669 participants contributed 26,363 person years of follow-up from 1994 to 2014. In 2015-2016, multivariate log-binomial/Poisson regression models examined violence predictors, including GBV history, substance use, HIV status, and transactional sex. Overall, 61% reported index GBV history; over follow-up, 10% reported sexual and 21% reported physical violence. Having experienced all three forms of past GBV posed the greatest risk (adjusted incidence rate ratio [AIRR]physical=2.23, 95% CI=1.57, 3.19; AIRRsexual=3.17, 95% CI=1.89, 5.31). Time-varying risk factors included recent transactional sex (AIRRphysical=1.29, 95% CI=1.03, 1.61; AIRRsexual=2.98, 95% CI=2.12, 4.19), low income (AIRRphysical=1.22, 95% CI=1.01, 1.45; AIRRsexual=1.38, 95% CI=1.03, 1.85), and marijuana use (AIRRphysical=1.43, 95% CI=1.22, 1.68; AIRRsexual=1.57, 95% CI=1.19, 2.08). For physical violence, time-varying risk factors additionally included housing instability (AIRR=1.37, 95% CI=1.15, 1.62); unemployment (AIRR=1.38, 95% CI=1.14, 1.67); exceeding seven drinks/week (AIRR=1.44, 95% CI=1.21, 1.71); and use of crack, cocaine, or heroin (AIRR=1.76, 95% CI=1.46, 2.11). Urban women living with HIV and their uninfected counterparts face sustained GBV risk. Past experiences of violence create sustained risk. Trauma-informed care, and addressing polyvictimization, structural inequality, transactional sex, and substance use treatment, can improve women's safety.

Change in Neighborhood Characteristics and Change in Coronary Artery Calcium: A Longitudinal Investigation in the MESA (Multi-Ethnic Study of Atherosclerosis) Cohort.

Although some evidence shows that neighborhood deprivation is associated with greater subclinical atherosclerosis, prior studies have not identified what aspects of deprived neighborhoods were driving the association. We investigated whether social and physical neighborhood characteristics are related to the progression of subclinical atherosclerosis in 5950 adult participants of the MESA (Multi-Ethnic Study of Atherosclerosis) during a 12-year follow-up period. We assessed subclinical disease using coronary artery calcium (CAC). Neighborhood features examined included density of recreational facilities, density of healthy food stores, and survey-based measures of availability of healthy foods, walking environment, and social environment. We used econometric fixed-effects models to investigate how change in a given neighborhood exposure is related to simultaneous change in subclinical atherosclerosis. Increases in density of neighborhood healthy food stores were associated with decreases in CAC (mean changes in CAC Agatston units per 1-SD increase in neighborhood exposures, -19.99; 95% confidence interval, -35.21 to -4.78) after adjustment for time-varying demographic confounders and computed tomography scanner type. This association remained similar in magnitude after additional adjustment for time-varying behavioral risk factors and depression. The addition of time-varying biomedical factors attenuated associations with CAC slightly (mean changes in CAC per 1-SD increase in neighborhood exposures, -17.60; 95% confidence interval, -32.71 to -2.49). Changes across time in other neighborhood measures were not significantly associated with within-person change in CAC. Results from this longitudinal study provide suggestive evidence that greater access to neighborhood healthy food resources may slow the development of coronary atherosclerosis in middle-aged and older adults.

Body mass index and adiposity indicators associated with cardiovascular biomarkers in youth with type 1 diabetes followed prospectively.

The impact of excess weight on cardiovascular disease risk in type 1 diabetes patients is unclear. This study examined associations of BMI and body composition with cardiovascular risk factors in youth followed prospectively for 18 months. The sample includes youth with type 1 diabetes (N = 136, baseline age = 12.3 ± 2.5y, glycated hemoglobin = 8.1 ± 1.1%) participating in an 18-month behavioral nutrition intervention trial. BMI, body composition (by dual energy x-ray absorptiometry), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C); triglycerides (TG), c-reactive protein (CRP), 8-iso-prostaglandin-F2alpha (8-iso-PGF2α), adiponectin and systolic and diastolic blood pressure (SBP and DBP, respectively) were assessed at clinic visits every 6 months. Random effects regression models for repeated measures estimated associations of time-varying BMI and body composition with time-varying cardiovascular risk factors, adjusted for treatment assignment and covariates. There was no intervention effect on cardiovascular risk factors. Percent body fat was positively associated with TG, LDL-C, CRP, SBP and DBP, while trunk fat mass and trunk %fat were associated positively with TG, LDL-C, CRP, SBP and DBP, and inversely with HDL-C. Higher BMI was associated with greater TG, CRP, SBP and DBP and lower HDL-C. BMI and body composition indicators were unrelated to 8-iso-PGF2α and adiponectin. Excess adiposity is associated with increased cardiovascular risk factors in this sample of youth with type 1 diabetes. Non-significant associations with adiponectin and 8-iso-PGF2α suggest potential differences from the general population in the role of adiposity in cardiovascular health.

Optimal selection of individuals for repeated covariate measurements in follow-up studies

Repeated covariate measurements bring important information on the time-varying risk factors in long epidemiological follow-up studies. However, due to budget limitations, it may be possible to carry out the repeated measurements only for a subset of the cohort. We study cost-efficient alternatives for the simple random sampling in the selection of the individuals to be remeasured. The proposed selection criteria are based on forms of the D-optimality. The selection methods are compared with the simulation studies and illustrated with the data from the East-West study carried out in Finland from 1959 to 1999. The results indicate that cost savings can be achieved if the selection is focused on the individuals with high expected risk of the event and, on the other hand, on those with extreme covariate values in the previous measurements.

Parental ADHD and Depression: Time-Varying Prediction of Offspring Externalizing Psychopathology

Parental attention deficit/hyperactivity disorder (ADHD) and depression are risk factors for negative child outcomes, but given their frequent co-occurrence and variability over time, developmentally sensitive studies are needed. To characterize change in parental ADHD and depression as predictors of change in child ADHD and oppositional defiant disorder (ODD), 230 five- to ten-year-old children with (n = 110) and without (n = 120) ADHD were followed prospectively for 2 years with 90% retention. At baseline and again 2 years later (i.e., Wave 2), parents self-reported their ADHD and depression; parents and teachers also separately rated child ADHD and ODD, as well as broader attention and externalizing problems. Controlling for child sex, race-ethnicity, age, and parental depression, generalized estimating equations revealed that 2-year decreases in parental ADHD significantly predicted reduced child ADHD symptoms, but only among non-ADHD youth. Alternatively, increasing parental depression positively predicted change in teacher-rated ODD symptoms. These findings provide quasi-experimental evidence that parental ADHD and depression may be time-varying risk factors with respect to key dimensions of child externalizing behavior problems. We consider the potential dynamic and reciprocal interrelations among parental ADHD and depression with developmental change in offspring ADHD and ODD. We also discuss implications of parent psychopathology in the development of interventions to reduce the burden of youth ADHD and associated externalizing behavior.

A Link Between Hypoglycemia and Progression of Atherosclerosis in the Veterans Affairs Diabetes Trial (VADT).

To determine whether a link exists between serious hypoglycemia and progression of atherosclerosis in a substudy of the Veterans Affairs Diabetes Trial (VADT) and to examine whether glycemic control during the VADT modified the association between serious hypoglycemia and coronary artery calcium (CAC) progression. Serious hypoglycemia was defined as severe episodes with loss of consciousness or requiring assistance or documented glucose <50 mg/dL. Progression of CAC was determined in 197 participants with baseline and follow-up computed tomography scans. During an average follow-up of 4.5 years between scans, 97 participants reported severe hypoglycemia (n = 23) or glucose <50 mg/dL (n = 74). Serious hypoglycemia occurred more frequently in the intensive therapy group than in the standard treatment group (74% vs. 21%, P < 0.01). Serious hypoglycemia was not associated with progression of CAC in the entire cohort, but the interaction between serious hypoglycemia and treatment was significant (P < 0.01). Participants with serious hypoglycemia in the standard therapy group, but not in the intensive therapy group, had ∼50% greater progression of CAC than those without serious hypoglycemia (median 11.15 vs. 5.4 mm(3), P = 0.02). Adjustment for all baseline differences, including CAC, or time-varying risk factors during the trial, did not change the results. Examining the effect of serious hypoglycemia by on-trial HbA1c levels (cutoff 7.5%) yielded similar results. In addition, a dose-response relationship was found between serious hypoglycemia and CAC progression in the standard therapy group only. Despite a higher frequency of serious hypoglycemia in the intensive therapy group, serious hypoglycemia was associated with progression of CAC in only the standard therapy group.

Time-Varying Risk Factors and Sexual Aggression Perpetration Among Male College Students

PurposePreventing sexual aggression (SA) can be informed by determining if time-varying risk factors differentiate men who follow different sexual aggression risk trajectories. MethodsData are from a longitudinal study with 795 college males surveyed at the end of each of their 4 years of college in 2008–2011. Repeated measures general linear models tested if changes in risk factors corresponded with sexual aggression trajectory membership. ResultsChanges in the risk factors corresponded with SA trajectories. Men who came to college with a history of SA but decreased their perpetration likelihood during college showed concurrent decreases in sexual compulsivity, impulsivity, hostile attitudes toward women, rape supportive beliefs, perceptions of peer approval of forced sex, and perceptions of peer pressure to have sex with many different women, and smaller increases in pornography use over their college years. Conversely, men who increased levels of SA over time demonstrated larger increases in risk factors in comparison to other trajectory groups. ConclusionsThe odds that males engaged in sexual aggression corresponded with changes in key risk factors. Risk factors were not static and interventions designed to alter them may lead to changes in sexual aggression risk.

Optimization of Equity Momentum: (How) Does it Work?

Standard mean-variance optimized momentum outperforms the traditional equally weighted momentum strategy if the expected return vector used reflects momentum's top and bottom only characteristic. This top and bottom only characteristic is the phenomenon that only the stocks in the top decile of momentum's ranking outperform and that only stocks in the bottom decile underperform, while all stocks in the intermediate deciles of the ranking have similar performance. If the optimization does not take this phenomenon into account the portfolio is also long the deciles 2 to 5 and short the deciles 6 to 9, while all these positions thus do not add anything to the return of the strategy. A new simplified bootstrapping methodology shows that the Sharpe-ratio of 52.8 percent of the optimized portfolio is significantly higher (p-value of 0.006) than the Sharpe-ratio of 29.3 percent for traditional equally weighted momentum. The optimized portfolio also exhibit less time-varying equity risk factor return exposures than traditional momentum and as such have more stable returns over the business cycle and have smaller drawdowns.

Volatility-of-volatility and tail risk hedging returns

This paper reports that the volatility-of-volatility implied by VIX options has predictability for tail risk hedging returns. Specifically, an increase in the volatility-of-volatility as measured by the VVIX index raises current prices of tail risk hedging options, such as S&P 500 puts and VIX calls, and lowers their subsequent returns over the next three to four weeks. The results are robust to jump risk, skewness, kurtosis, option liquidity, variance risk premium, and limit of arbitrage. The predictability can be explained by either risk premiums for a time-varying crash risk factor or uncertainty premiums for a time-varying uncertain belief in volatility.

Effects of return expectation on mutual funds’ risk exposures

We use market-wide implied cost of capital to investigate changes in mutual funds’ risk exposures. Our approach is solely based on market information at the respective time and seems natural, as analysts and fund managers possess similar knowledge and skills. Using a sample of 4147 US equity mutual funds, we provide evidence for time-varying risk exposures for all funds, independent of their style and size focus. Furthermore, value (growth) funds reduce their value (momentum) loadings in times of a high expected market risk premium. However, only for small- and mid-cap funds, this beneficial behavior can be attributed to active management. After controlling for time-varying risk factors, all fund types perform equally poorly measured by their alpha.

Investor sentiment, customer satisfaction and stock returns

Purpose– This study aims to investigate whether and how different sentiments affect the stock market’s reaction to the American Customer Satisfaction Index (ACSI) information.Design/methodology/approach– The portfolio approach, with time-varying risk factor loadings and the asset-pricing models, is borrowed from the finance literature to investigate the ACSI-performance relationship. A direct sentiment index is used to examine how investors’ optimistic, neutral and pessimistic sentiments affect the aforementioned relation.Findings– This paper finds that customer satisfaction is a valuable intangible asset that generates positive abnormal returns. On average, investing in the Strong-ACSI Portfolio is superior to investing in the market index. Even when the stock market holds pessimistic beliefs, investors can beat the market by investing in firms that score well on customer satisfaction. The out-performance of our zero-cost, long–short ACSI strategy also confirms the mispricing of ACSI information in pessimistic periods.Research limitations/implications– Findings are limited to firms covered by the ACSI data.Practical implications– Finance research has further documented evidence of the stock market under-reacting to intangible information. For example, firms with higher research and development expenditures, advertising, patent citations and employee satisfaction all earn superior returns. Literature also proves that investors efficiently react to tangible information, whereas they undervalue intangible information. In summary, combining our results and those reported in the literature, customer satisfaction is value-relevant for both investors and firm management, particularly in pessimistic periods.Originality/value– This study is the first to investigate how sentiment affects the positive ACSI-performance relationship, while considering the time-varying property of risk factors. This study is also the first to show that ACSI plays a more important role during pessimistic periods. This study contributes to the growing literature on the marketing–finance interface by providing better understanding of how investor emotional states affect their perceptions and valuations of customer satisfaction.

A New Portfolio Formation Approach to Mispricing of Marketing Performance Indicators: an Application to Customer Satisfaction

The mispricing of marketing performance indicators (e.g., brand equity, churn, and customer satisfaction) is an important element of arguments in favor of the financial value of marketing investments. Evidence for mispricing can be assessed by examining whether or not portfolios composed of firms that load highly on marketing performance indicators deliver excess returns. Unfortunately, extant portfolio formation methods that require the use of a risk model are open to the criticism of time-varying risk factor loadings due to the changing composition of the portfolio over time. This is a serious critique as the direction of the induced bias is unknown. As an alternative, we propose a new method and construct portfolios that are neutral with respect to the desired risk factors a priori. Consequently, no risk model is needed when analyzing the observed returns of our portfolios. We apply our method to a frequently studied marketing performance indicator, customer satisfaction, and using various ways of measuring customer satisfaction, we do not find any convincing evidence that portfolios that load on high customer satisfaction lead to abnormal returns.