Product-limit survival functions with correlated survival times

Prenatal exposure to a natural disaster and early development of psychiatric disorders during the preschool years: stress in pregnancy study

BACKGROUND

Growing evidence shows an association between in utero exposure to natural disasters and child behavioral problems, but we still know little about the development of specific psychopathology in preschool-aged children.

METHODS

Preschool children (n = 163, mean age = 3.19, 85.5% racial and ethnic minorities) and their parents (n = 151) were evaluated annually at ages 2-5 to assess the emergence of psychopathology using the Preschool Age Psychopathological Assessment (PAPA), a parent-report structured diagnostic interview developed for preschool-age children. Sixty-six (40.5%) children were exposed to Sandy Storm (SS) in utero and 97 (59.5%) were not. Survival analysis evaluated patterns of onset and estimated cumulative risks of psychopathology among exposed and unexposed children, in total and by sex. Analyses were controlled for the severity of objective and subjective SS-related stress, concurrent family stress, and demographic and psychosocial confounders, such as maternal age, race, SES, maternal substance use, and normative prenatal stress.

RESULTS

Exposure to SS in utero was associated with a substantial increase in depressive disorders (Hazard Ratio (HR) = 16.9, p = .030), anxiety disorders (HR = 5.1, p < .0001), and attention-deficit/disruptive behavioral disorders (HR = 3.4, p = .02). Diagnostic rates were elevated for generalized anxiety disorder (GAD; HR = 8.5, p = .004), attention-deficit/hyperactivity disorder (ADHD; HR = 5.5, p = .01), oppositional-defiant disorder (ODD; HR = 3.8, p = .05), and separation-anxiety disorder (SAD; HR = 3.5, p = .001). Males had distinctively elevated risks for attention-deficit/disruptive behavioral disorders (HR = 7.8, p = .02), including ADHD, CD, and ODD, whereas females had elevated risks for anxiety disorders (HR = 10.0, p < .0001), phobia (HR = 2.8, p = .02) and depressive disorders (HR = 30.0, p = .03), including SAD, GAD, and dysthymia.

CONCLUSIONS

The findings demonstrate that in utero exposure to a major weather-related disaster (SS) was associated with increased risk for psychopathology in children and provided evidence of distinct psychopathological outcomes as a function of sex. More attention is needed to understand specific parent, child, and environmental factors which account for this increased risk, and to develop mitigation strategies.

Association of maternal exposure to Superstorm Sandy and maternal cannabis use with development of psychopathology among offspring: the Stress in Pregnancy Study

BACKGROUND

Early-life adverse experiences can elevate the magnitude of the risk of developmental psychopathology, but the potential synergistic effects of multiple factors have not been well studied.

AIMS

To determine whether prenatal exposures to maternal stress (Superstorm Sandy) and maternal cannabis use synergistically alter the risk of developmental psychopathology.

METHOD

The study included 163 children (53.4% girls), longitudinally tracked (ages 2-5 years) in relation to the effects of two early-life adverse exposures (Superstorm Sandy and maternal cannabis use). Offspring were grouped by exposure status (neither, only maternal cannabis use, only Superstorm Sandy or both). DSM-IV disorders for offspring were derived from structured clinical interviews; caregiver-reported ratings of family stress and social support were also assessed.

RESULTS

A total of 40.5% had been exposed to Superstorm Sandy and 24.5% to maternal cannabis use. Offspring exposed to both (n = 13, 8.0%), relative to those exposed to neither, had a 31-fold increased risk of disruptive behavioural disorders (DBDs) and a seven-fold increased risk of anxiety disorders. The synergy index demonstrated that offspring with two exposures had synergistic elevation in risk of DBDs (synergy index, 2.06, P = 0.03) and anxiety disorders (synergy index, 2.60, P = 0.004), compared with the sum of single risks. Offspring with two exposures had the highest parenting stress and lowest social support.

CONCLUSIONS

Our findings are consistent with the double-hit model suggesting that offspring with multiple early-life adverse exposures (Superstorm Sandy and maternal cannabis use) have synergistically increased risks of mental health problems. Given the increasing frequency of major natural disasters and cannabis use, especially among women under stress, these findings have significant public health implications.

Replication and Validation of a State-Wide Linkage Method to Estimate Incidence Proportion of Child Maltreatment

PURPOSE

To study familial factors associated with child maltreatment in a birth population, Alaska piloted a mixed-design method that linked child welfare data with the Pregnancy Risk Assessment Monitoring System (PRAMS). We replicated this approach in Oregon and validated it in both states.

METHODS

We linked vital records, child welfare, and PRAMS data to create two 2009 birth cohorts for each state: one based on vital records (full birth cohort), and one on PRAMS (stratified random sample). For each cohort we estimated the incidence proportions (IP) of child maltreatment before age nine years and compared those estimated using PRAMS with those observed using the full birth cohort.

RESULTS

The Oregon PRAMS cohort estimated that 28.7% (95% CI: 24.0, 33.4), 20.9% (17.1, 24.7), and 8.3% (6.0, 10.5) of children experienced an alleged, investigated, and substantiated maltreatment respectively, versus 32.0%, 25.0% and 9.9% from the birth cohort. The corresponding Alaska estimates were 29.1% (26.1, 32.0), 22.6% (19.9, 25.2), and 8.3% (6.7, 9.9) of children from the PRAMS cohort versus 29.1%, 23.5%, and 9.1% in the birth cohort.

CONCLUSIONS

The incidence proportion of child maltreatment in two states was accurately estimated with PRAMS cohorts. Researchers can study a comprehensive set of factors that may influence child maltreatment by incorporating PRAMS into birth cohort linkages.

Identification and development of TP53 mutation-associated Long non-coding RNAs signature for optimized prognosis assessment and treatment selection in hepatocellular carcinoma

BACKGROUND

The TP53 gene is estimated to be mutated in over 50% of tumors, with the majority of tumors exhibiting abnormal TP53 signaling pathways. However, the exploration of TP53 mutation-related LncRNAs in Hepatocellular carcinoma (HCC) remains incomplete. This study aims to identify such LncRNAs and enhance the prognostic accuracy for Hepatoma patients.

MATERIAL AND METHODS

Differential gene expression was identified using the "limma" package in R. Prognosis-related LncRNAs were identified via univariate Cox regression analysis, while a prognostic model was crafted using multivariate Cox regression analysis. Survival analysis was conducted using Kaplan-Meier curves. The precision of the prognostic model was assessed through ROC analysis. Subsequently, the Tumor Immune Dysfunction and Exclusion (TIDE) algorithm were executed on the TCGA dataset via the TIDE database. Fractions of 24 types of immune cell infiltration were obtained from NCI Cancer Research Data Commons using deconvolution techniques. The protein expression levels encoded by specific genes were obtained through the TPCA database.

RESULTS

In this research, we have identified 85 LncRNAs associated with TP53 mutations and developed a corresponding signature referred to as TP53MLncSig. Kaplan-Meier analysis revealed a lower 3-year survival rate in high-risk patients (46.9%) compared to low-risk patients (74.2%). The accuracy of the prognostic TP53MLncSig was further evaluated by calculating the area under the ROC curve. The analysis yielded a 5-year ROC score of 0.793, confirming its effectiveness. Furthermore, a higher score for TP53MLncSig was found to be associated with an increased response rate to immune checkpoint blocker (ICB) therapy (p = .005). Patients possessing high-risk classification exhibited lower levels of P53 protein expression and higher levels of genomic instability.

CONCLUSION

The present study aimed to identify and validate LncRNAs associated with TP53 mutations. We constructed a prognostic model that can predict chemosensitivity and response to ICB therapy in HCC patients. This novel approach sheds light on the role of LncRNAs in TP53 mutation and provides valuable resources for analyzing patient prognosis and treatment selection.

Comparative Safety of the TFN-ADVANCED Proximal Femoral Nailing System: Findings from a U.S. Health-Care Database

BACKGROUND

Proximal femoral fractures are often treated with cephalomedullary nails. Although nail breakages following fracture repair are infrequent, a recent implant retrieval study suggested that the TFN-ADVANCED (TFNA) Proximal Femoral Nailing System (DePuy Synthes) was susceptible to post-implant breakage. It is unclear whether the risk of breakage among patients who receive the TFNA implant is higher than patients who receive other comparable cephalomedullary nails. The current study was designed to evaluate the comparative risk of breakage of the TFNA nail.

METHODS

Using data from a large U.S. health-care database, the current study was designed to determine whether TFNA nails have equal, lower, or higher risk of breakage relative to all other comparable, single-head-element (with no additional lag screws), cephalomedullary nails, the Stryker Gamma3 and the Zimmer Natural Nail, referred to in this study as the non-TFNA group. Data were from patients who received the TFNA implant or non-TFNA nails in 365 hospitals between February 1, 2014, and September 30, 2019. Analysis of nail breakage post-implantation was prespecified as the difference between the TFNA group and the non-TFNA group in cumulative incidence at 18 months, with a prespecified equivalence margin of 0.5%, using data balanced on measured covariates by propensity score weighting.

RESULTS

Within the first 18 months of implantation, in 14,370 patients with TFNA nails, there were 27 nail breakages, and in 8,260 patients with non-TFNA nails, there were 29 nail breakages. The mean time to nail breakage was 4.72 months for the TFNA group and 4.05 months for the non-TFNA group. In the balanced data, the risk of breakage at 18 months was 0.26% (95% confidence interval [CI], 0.17% to 0.36%) for the TFNA group and 0.25% (95% CI, 0.05% to 0.45%) for the non-TFNA group, with a risk difference of 0.01% (95% CI, -0.21% to 0.24%). This result indicates that the cumulative incidence of nail breakage was equivalent (between -0.5% and 0.5%) for both nail groups. The risk differences were also within the equivalence margin in subgroup analyses: pertrochanteric fractures only (-0.08% [95% CI, -0.34% to 0.19%]), pertrochanteric or subtrochanteric fractures (-0.04% [95% CI, -0.29% to 0.21%]), and those with International Classification of Diseases, Tenth Revision (ICD-10) data only (0.03% [95% CI, -0.18% to 0.25%]).

CONCLUSIONS

The risk of nail breakage was equivalent for TFNA and comparator cephalomedullary nails.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Methodological review showed that time-to-event outcomes are often inadequately handled in cluster randomized trials

OBJECTIVES

To estimate the prevalence of time-to-event (TTE) outcomes in cluster randomized trials (CRTs) and to examine their statistical management.

STUDY DESIGN AND SETTING

We searched PubMed to identify primary reports of CRTs published in six major general medical journals (2013-2018). Nature of outcomes and, for TTE outcomes, statistical methods for sample size, analysis, and measures of intracluster correlation were extracted.

RESULTS

A TTE analysis was used in 17% of the CRTs (32/184) either as a primary or secondary outcome analysis, or in a sensitivity analysis. Among the five CRTs with a TTE primary outcome, two accounted for both intracluster correlation and the TTE nature of the outcome in sample size calculation; one reported a measure of intracluster correlation in the analysis. Among the 32 CRTs with a least one TTE analysis, 44% (14/32) accounted for clustering in all TTE analyses. We identified 12 additional CRTs in which there was at least one outcome not analyzed as TTE for which a TTE analysis might have been preferred.

CONCLUSION

TTE outcomes are not uncommon in CRTs but appropriate statistical methods are infrequently used. Our results suggest that further methodological development and explicit recommendations for TTE outcomes in CRTs are needed.

MRI Texture Analysis for the Prediction of Stereotactic Radiosurgery Outcomes in Brain Metastases from Lung Cancer

This study aims to evaluate the utility of texture analysis in predicting the outcome of stereotactic radiosurgery (SRS) for brain metastases from lung cancer. From 83 patients with lung cancer who underwent SRS for brain metastasis, a total of 118 metastatic lesions were included. Two neuroradiologists independently performed magnetic resonance imaging (MRI)-based texture analysis using the Imaging Biomarker Explorer software. Inter-reader reliability as well as univariable and multivariable analyses were performed for texture features and clinical parameters to determine independent predictors for local progression-free survival (PFS) and overall survival (OS). Furthermore, Harrell’s concordance index (C-index) was used to assess the performance of the independent texture features. The primary tumor histology of small cell lung cancer (SCLC) was the only clinical parameter significantly associated with local PFS in multivariable analysis. Run-length non-uniformity (RLN) and short-run emphasis were the independent texture features associated with local PFS. In the non-SCLC (NSCLC) subgroup analysis, RLN and local range mean were associated with local PFS. The C-index of independent texture features was 0.79 for the all-patients group and 0.73 for the NSCLC subgroup. In conclusion, texture analysis on pre-treatment MRI of lung cancer patients with brain metastases may have a role in predicting SRS response.

Neoadjuvant Chemoradiation Compared With Neoadjuvant Radiation Alone in the Management of High-Grade Soft Tissue Extremity Sarcomas

Purpose

Patients with large, high-grade soft tissue sarcomas are commonly treated with aggressive limb preservation regimens. This study aimed to assess cancer control outcomes of patients treated with neoadjuvant chemoradiation (CRT) compared with radiation therapy (RT) alone.

Methods

We reviewed records of patients with high-grade extremity or trunk soft tissue sarcomas ≥5 cm who were treated with neoadjuvant radiation with or without chemotherapy. Patient and disease characteristics were compared using t test and χ² tests. Standardized mortality ratio weighted method was used to compare overall survival (OS), local control, and disease-free (DFS) survival. Acute radiation and surgical toxicity were reported.

Results

In the study, 64 patients (34 CRT and 30 RT) treated between 1997 and 2015 were analyzed. In the RT group compared with the CRT group, the patient population was older, with a median age of 65 versus 50 years (P < .001), and more likely to have cardiovascular disease (CVD; 30% vs 0%, P < .001). At a median follow-up of 41 months, after adjusting for propensity score of receiving RT, the 3-year LC was 87.3% versus 86.1%, DFS was 58.5% versus 56.6%, and OS was 75.6% versus 69.0% for the CRT and RT groups, respectively (P > .05). Acute dermatitis occurred in 18% versus 3% and surgical complications occurred in 32% versus 17% of CRT and RT patients, respectively.

Conclusions

In this study, patients receiving RT alone were more likely to be older and have comorbid cardiovascular disease. When controlling for baseline differences, neoadjuvant CRT and RT provided similar rates of LC, DFS, and OS.

Stainless steel crowns as a restoration for permanent posterior teeth in people with special needs: A retrospective study

BACKGROUND

Limited information exists regarding the use of stainless steel crowns (SSCs) in permanent teeth. The objective of this retrospective cohort study was to present the long-term clinical outcomes of the SSC compared with those of amalgam and composite resin restorations and the SSC radiographic outcomes in a special-needs population.

METHODS

This study included 271 patients with at least 1 SSC restoration from the Mount Sinai Hospital Dentistry Clinic for Persons with Special Needs in Toronto, Ontario, Canada. A total of 2,621 posterior permanent tooth restorations were documented: 766 SSCs, 1,651 amalgam restorations, and 204 composite resin restorations. Clinical analysis included patient demographics, treatment parameters, and outcome assessments for each restoration recorded. Radiographic analysis of SSC restorations included 127 bite-wing radiographs and 118 periapical radiographs, measurement of interproximal bone loss, and assessment of periapical status using the Periapical Index Scale.

RESULTS

The 10-year survival rates for new SSC and amalgam restorations were 79.2% and 63.5%, respectively. The 91 SSC failures included 2 recementations, 33 replacements, and 56 extractions. Primary diagnoses at the time of failure included chronic periodontal disease (25) and loose or lost SSCs (24). Of the 528 failed conventional restorations that were replaced, 60% were replaced with SSCs. The mean alveolar bone loss from mesial and distal sites was 1.36 millimeters and 1.40 mm, respectively. Therefore, 93% of the sites recorded were less than 2 mm and classified as healthy. All pre-SCC and post-SSC periapical radiographs had healthy Periapical Index Scale scores (1 or 2) recorded over an average duration of 8.4 years (1-29.1 years).

CONCLUSIONS

SSCs are a durable treatment option for the restoration of the posterior permanent dentition.

PRACTICAL IMPLICATIONS

Posterior permanent teeth restored with stainless steel crowns can be expected to last for 10 years and represent a viable treatment choice for severely carious or fractured posterior permanent teeth.

APOE-related risk of mild cognitive impairment and dementia for prevention trials: An analysis of four cohorts

BACKGROUND

With the onset of prevention trials for individuals at high risk for Alzheimer disease, there is increasing need for accurate risk prediction to inform study design and enrollment, but available risk estimates are limited. We developed risk estimates for the incidence of mild cognitive impairment (MCI) or dementia among cognitively unimpaired individuals by APOE-e4 dose for the genetic disclosure process of the Alzheimer's Prevention Initiative Generation Study, a prevention trial in cognitively unimpaired APOE-e4/e4 homozygote individuals.

METHODS AND FINDINGS

We included cognitively unimpaired individuals aged 60-75 y, consistent with Generation Study eligibility criteria, from the National Alzheimer's Coordinating Center (NACC) (n = 5,073, 158 APOE-e4/e4), the Rotterdam Study (n = 6,399, 156 APOE-e4/e4), the Framingham Heart Study (n = 4,078, 67 APOE-e4/e4), and the Sacramento Area Latino Study on Aging (SALSA) (n = 1,294, 11 APOE-e4/e4). We computed stratified cumulative incidence curves by age (60-64, 65-69, 70-75 y) and APOE-e4 dose, adjusting for the competing risk of mortality, and determined risk of MCI and/or dementia by genotype and baseline age. We also used subdistribution hazard regression to model relative hazard based on age, APOE genotype, sex, education, family history of dementia, vascular risk, subjective memory concerns, and baseline cognitive performance. The four cohorts varied considerably in age, education, ethnicity/race, and APOE-e4 allele frequency. Overall, cumulative incidence was uniformly higher in NACC than in the population-based cohorts. Among APOE-e4/e4 individuals, 5-y cumulative incidence was as follows: in the 60-64-y age stratum, it ranged from 0% to 5.88% in the three population-based cohorts versus 23.06% in NACC; in the 65-69-y age stratum, from 9.42% to 10.39% versus 34.62%; and in the 70-75-y age stratum, from 18.64% to 33.33% versus 38.34%. Five-year incidence of dementia was negligible except for APOE-e4/e4 individuals and those over 70 y. Lifetime incidence (to age 80-85 y) of MCI or dementia for the APOE-e4/e4 individuals in the long-term Framingham and Rotterdam cohorts was 34.69%-38.45% at age 60-64 y, 30.76%-40.26% at 65-69 y, and 33.3%-35.17% at 70-75 y. Confidence limits for these estimates are often wide, particularly for APOE-e4/e4 individuals and for the dementia outcome at 5 y. In regression models, APOE-e4 dose and age both consistently increased risk, as did lower education, subjective memory concerns, poorer baseline cognitive performance, and family history of dementia. We discuss several limitations of the study, including the small numbers of APOE-e4/e4 individuals, missing data and differential dropout, limited ethnic and racial diversity, and differences in definitions of exposure and outcome variables.

CONCLUSIONS

Estimates of the absolute risk of MCI or dementia, particularly over short time intervals, are sensitive to sampling and a variety of methodological factors. Nonetheless, such estimates were fairly consistent across the population-based cohorts, and lower than those from a convenience cohort and those estimated in prior studies-with implications for informed consent and design for clinical trials targeting high-risk individuals.

Safe Reduction in CD4 Cell Count Monitoring in Stable, Virally Suppressed Patients With HIV Infection or HIV/Hepatitis C Virus Coinfection

BACKGROUND

It has been suggested that routine CD4 cell count monitoring in human immunodeficiency virus (HIV)-monoinfected patients with suppressed viral loads and CD4 cell counts >300 cell/μL could be reduced to annual. HIV/hepatitis C virus (HCV) coinfection is frequent, but evidence supporting similar reductions in CD4 cell count monitoring is lacking for this population. We determined whether CD4 cell count monitoring could be reduced in monoinfected and coinfected patients by estimating the probability of maintaining CD4 cell counts ≥200 cells/µL during continuous HIV suppression.

METHODS

The PISCIS Cohort study included data from 14 539 patients aged ≥16 years from 10 hospitals in Catalonia and 2 in the Balearic Islands (Spain) since January 1998. All patients who had at least one period of 6 months of continuous HIV suppression were included in this analysis. Cumulative probabilities with 95% confidence intervals were calculated using the Kaplan-Meier estimator stratified by the initial CD4 cell count at the period of continuous suppression initiation.

RESULTS

A total of 8695 patients were included. CD4 cell counts fell to <200 cells/µL in 7.4% patients, and the proportion was lower in patients with an initial count >350 cells/µL (1.8%) and higher in those with an initial count of 200-249 cells/µL (23.1%). CD4 cell counts fell to <200 cells/µL in 5.7% of monoinfected and 11.1% of coinfected patients. Of monoinfected patients with an initial CD4 cell count of 300-349 cells/µL, 95.6% maintained counts ≥200 cells/µL. In the coinfected group with the same initial count, this rate was lower, but 97.6% of coinfected patients with initial counts >350 cells/µL maintained counts ≥200 cells/µL.

CONCLUSIONS

From our data, it can be inferred that CD4 cell count monitoring can be safely performed annually in HIV-monoinfected patients with CD4 cell counts >300 cells/µL and HIV/HCV-coinfected patients with counts >350 cells/µL.

Nonparametric restricted mean analysis across multiple follow-up intervals

We provide a nonparametric estimate of τ-restricted mean survival using follow-up information beyond τwhen appropriate to improve precision. The variance accounts for correlation between follow-up windows. Both asymptotic calculations and simulation studies recommend follow-up intervals spaced approximately τ/2 apart.

DSM-IV and DSM-5 social anxiety disorder in the Australian community

OBJECTIVE

Current and accurate estimates of prevalence, correlates, comorbid concerns and treatment-seeking behaviours associated with disorders are essential for informing policy, clinical practice and research. The most recent snapshot of social anxiety disorder in Australia was published more than a decade ago, with significant changes to the accessibility of mental health treatment services and diagnostic measures occurring during this period. This paper aims to (i) update the understanding of social anxiety disorder, its associations and patterns of treatment-seeking behaviours in the Australian population, and (ii) explore the impact of revised diagnostic criteria detailed in the Fifth Edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) on prevalence estimates.

METHODS

The National Survey of Mental Health and Wellbeing (NSMHWB) was conducted by the Australian Bureau of Statistics in 2007, collecting information from a nationally representative random sample of 8841 Australians aged 16-85 years. The presence of social anxiety disorder diagnostic criteria and related disorders were assessed over 12 months and lifetime periods using the World Mental Health Composite International Diagnostic Interview.

RESULTS

Profiles of social anxiety disorder were consistent with previous estimates, with higher prevalence in females and younger age groups. Of the 8.4% of Australians meeting criteria for social anxiety disorder at some point in their lifetime (12-month prevalence 4.2%), a majority also experienced comorbid mental health concerns (70%). The revised performance-only specifier included in the DSM-5 was applicable to only 0.3% of lifetime cases. Just over 20% of people reporting social anxiety disorder as their primary concern sought treatment, most commonly through general practitioners.

CONCLUSIONS

Social anxiety disorder continues to be prevalent in the Australian population and highly related to other disorders, yet few people experiencing social anxiety disorder seek treatment.

Survival estimation in two-phase cohort studies with application to biomarkers evaluation

Two-phase studies are attractive for their economy and efficiency in research settings where large cohorts are available for investigating the prognostic and predictive role of novel genetic and biological factors. In this type of study, information on novel factors is collected only in a convenient subcohort (phase II) drawn from the cohort (phase I) according to a given (optimal) sampling strategy. Estimation of survival in the subcohort needs to account for the design. The Kaplan-Meier method, based on counts of events and of subjects at risk in time, must be applied accounting, with suitable weights, for the sampling probabilities of the subjects in phase II, in order to recover the representativeness of the subcohort for the entire cohort. The authors derived a proper variance estimator of survival by linearization. The proposed method is applied in the context of a two-phase study on childhood acute lymphoblastic leukemia, which was planned in order to evaluate the role of genetic polymorphisms on treatment failure due to relapse. The method has shown satisfactory performance through simulations under different scenarios, including the case-control setting, and proved to be useful for describing results in the clinical example.

Nonparametric tests of treatment effect based on combined endpoints for mortality and recurrent events

Terminal events are commonly combined with other outcomes to improve the power for detecting treatment effects in clinical studies. This manuscript explores novel ways to combine information on terminal and recurrent events in constructing two-sample tests. Existing approaches follow either a time-to-first event analysis approach or a recurrent event modeling approach. Nonparametric recurrent event analyses are often restricted by independence assumptions on gap times between events. Although time-to-first event analyses are not subject to this restriction, they discard information that occurs beyond the initial event and are much less powerful for detecting treatment differences. We develop two new approaches for determining treatment effects, motivated by less restrictive assumptions of time-to-first event analyses that combine information from multiple follow-up intervals. The first testing procedure pools (correlated) short-term τ -restricted outcomes from prespecified intervals starting at times t(k), k = 1, . . . , b, and compares estimated τ -restricted mean survival across treatment groups from this combined dataset. The second procedure calculates conditional τ-restricted means from those at risk at times t(k), k = 1, . . . , b, and compares the area under a function of these by treatment. Variances calculations, taking into account correlation of short-term outcomes within individuals, linearize random components of the test statistics following Woodruff (1971. A simple method for approximating the variance of a complicated estimate. Journal of the American Statistical Association 66, 411-414) and more recently Williams (1995. Product-limit survival functions with correlated survival times. Lifetime Data Analysis 1, 171-186). Simulations compare the finite sample performance of our tests to the robust proportional rates model proposed by Lin and others (2000. Semiparametric regression for the mean and rate functions of recurrent events. Journal of the Royal Statistical Society: Series B (Statistical Methodology) 62(4), 711-730) and the Ghosh and Lin (2000. Non-parametric analysis of recurrent events and death. Biometrics 56(2), 554-562) combined test for recurrent events and death. For different treatment effect patterns the proposed methods perform favorably when compared with existing methods. These new analysis approaches also produce correct type I error rates with correlated gap times between events. New methods are applied to data from a trial of azithromycin in patients with chronic obstructive pulmonary disease.

Population-based absolute risk estimation with survey data

Absolute risk is the probability that a cause-specific event occurs in a given time interval in the presence of competing events. We present methods to estimate population-based absolute risk from a complex survey cohort that can accommodate multiple exposure-specific competing risks. The hazard function for each event type consists of an individualized relative risk multiplied by a baseline hazard function, which is modeled nonparametrically or parametrically with a piecewise exponential model. An influence method is used to derive a Taylor-linearized variance estimate for the absolute risk estimates. We introduce novel measures of the cause-specific influences that can guide modeling choices for the competing event components of the model. To illustrate our methodology, we build and validate cause-specific absolute risk models for cardiovascular and cancer deaths using data from the National Health and Nutrition Examination Survey. Our applications demonstrate the usefulness of survey-based risk prediction models for predicting health outcomes and quantifying the potential impact of disease prevention programs at the population level.

Estimation of finite population duration distributions from longitudinal survey panels with intermittent followup

We consider survival or duration times associated with spells (sojourns in some state) or events experienced by individuals in a population over a specified time period. Duration distributions can be estimated from data recorded during followup of panel members in longitudinal surveys, but adjustments for the sample design, population structure and losses to followup are typically required. We provided weighted Kaplan-Meier estimates that allow for these features and, in particular, adjust for dependent loss to followup through the use of inverse probability of censoring weights.

Preclinical episodes of orofacial pain symptoms and their association with health care behaviors in the OPPERA prospective cohort study

The course of preclinical pain symptoms sheds light on the etiology and prognosis of chronic pain. We aimed to quantify rates of developing initial and recurrent symptoms of painful temporomandibular disorder (TMD) and to evaluate associations with health behaviors. In the OPPERA prospective cohort study, 2,719 individuals aged 18 to 44years with lifetime absence of TMD when enrolled completed 25,103 quarterly (3-monthly) questionnaires during a median 2.3-year follow-up period. Questionnaires documented TMD symptom episodes, headache, other body pain, health care attendance, and analgesic use, and. Kaplan-Meier methods for clustered data estimated symptom-free survival time. Multivariable models assessed demographic variation in TMD symptom rates and evaluated associations with health care and analgesic use. One-third of the study subjects developed TMD symptoms and for a quarter of symptomatic episodes, pain intensity was severe. Initial TMD symptoms developed at an annual rate of 18.8 episodes per 100 persons. The annual rate more than doubled for first-recurrence and doubled again for second or subsequent recurrence such that, 1year after first recurrence, 71% of study subjects experienced a second recurrence. The overall rate increased with age and was greater in African Americans and lower in Asians relative to those of white race/ethnicity. The probability of TMD symptoms was strongly associated with concurrent episodes of headache and body pain and with past episodes of TMD symptoms. Episodes of TMD symptoms, headache, and body pain were associated with increases of ∼10% in probability of analgesic use and health care attendance. Yet, even when TMD, headache, and body pain occurred concurrently, 27% of study subjects neither attended health care nor used analgesics.

Is frequent CD4+ T-lymphocyte count monitoring necessary for persons with counts >=300 cells/μL and HIV-1 suppression?

Among patients infected with human immunodeficiency virus (HIV), those with HIV-1 RNA <200 copies/mL and CD4 counts ≥300 cells/µL had a 97.1% probability of maintaining durable CD4 ≥200 cells/µL for 4 years. When non-HIV causes of CD4 lymphopenia were excluded, the probability rose to 99.2%. Our data support less frequent CD4 monitoring during viral suppression.

Life-time risk for substance use among offspring of abusive family environment from the community

The current study examined the cumulative risk, age of initiation, and functional impairments among adults with substance use problems (N = 1748) by child abuse status. Child abuse was associated with earlier initiation of marijuana, cocaine, and heroin use, and had greater risks for all the drugs studied (hazard ratios, 1.7-3.2). Furthermore, child abuse was associated with increased medical and functional impairments, including ER visits, health problems, drug dealing, drug dependence, and drug cravings. Provision of social services and parenting education during the perinatal period may prevent the long-term impact of child abuse on substance use and related impairments. The study's limitations are noted.

Maternal smoking during pregnancy and risk of alcohol use disorders among adult offspring

OBJECTIVE

The aim of this study was to evaluate the association between maternal smoking during pregnancy (MSP) and lifetime risk for alcohol use disorder (AUD) and to explore possible mechanisms through which MSP may be related to neurobehavioral conditions during infancy and childhood, which could, in turn, lead to increased risk for AUD.

METHOD

A sample of 1,625 individuals was followed from pregnancy for more than 40 years. Capitalizing on the long follow-up time, we used survival analysis to examine lifetime risks of AUD (diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) in relation to levels of MSP (none, <20 cigarettes/day, and ≥20 cigarettes/day). We then used structural equation modeling to test hypotheses regarding potential mechanisms, including lower birth weight, neurological abnormalities, poorer academic functioning, and behavioral dysregulation.

RESULTS

Relative to unexposed offspring, offspring of mothers who smoked 20 cigarettes per day or more exhibited greater risks for AUD (hazard ratio = 1.31, 95% CI [1.08, 1.59]). However, no differences were observed among offspring exposed to fewer than 20 cigarettes per day. In structural equation models, MSP was associated with neurobehavioral problems during infancy and childhood, which, in turn, were associated with an increased risk for adult AUD.

CONCLUSIONS

MSP was associated with an increased lifetime risk for AUD. Adverse consequences were evident from birth to adulthood. A two-pronged remedial intervention targeted at both the mother (to reduce smoking during pregnancy) and child (to improve academic functioning) may reduce the risk for subsequent AUD.

Applying sample survey methods to clinical trials data

This paper outlines the utility of statistical methods for sample surveys in analysing clinical trials data. Sample survey statisticians face a variety of complex data analysis issues deriving from the use of multi-stage probability sampling from finite populations. One such issue is that of clustering of observations at the various stages of sampling. Survey data analysis approaches developed to accommodate clustering in the sample design have more general application to clinical studies in which repeated measures structures are encountered. Situations where these methods are of interest include multi-visit studies where responses are observed at two or more time points for each patient, multi-period cross-over studies, and epidemiological studies for repeated occurrences of adverse events or illnesses. We describe statistical procedures for fitting multiple regression models to sample survey data that are more effective for repeated measures studies with complicated data structures than the more traditional approaches of multivariate repeated measures analysis. In this setting, one can specify a primary sampling unit within which repeated measures have intraclass correlation. This intraclass correlation is taken into account by sample survey regression methods through robust estimates of the standard errors of the regression coefficients. Regression estimates are obtained from model fitting estimation equations which ignore the correlation structure of the data (that is, computing procedures which assume that all observational units are independent or are from simple random samples). The analytic approach is straightforward to apply with logistic models for dichotomous data, proportional odds models for ordinal data, and linear models for continuously scaled data, and results are interpretable in terms of population average parameters. Through the features summarized here, the sample survey regression methods have many similarities to the broader family of methods based on generalized estimating equations (GEE). Sample survey methods for the analysis of time-to-event data have more recently been developed and implemented in the context of finite probability sampling. Given the importance of survival endpoints in late phase studies for drug development, these methods have clear utility in the area of clinical trials data analysis. A brief overview of methods for sample survey data analysis is first provided, followed by motivation for applying these methods to clinical trials data. Examples drawn from three clinical studies are provided to illustrate survey methods for logistic regression, proportional odds regression and proportional hazards regression. Potential problems with the proposed methods and ways of addressing them are discussed.

A note on robust variance estimation for cluster-correlated data

There is a simple robust variance estimator for cluster-correlated data. While this estimator is well known, it is poorly documented, and its wide range of applicability is often not understood. The estimator is widely used in sample survey research, but the results in the sample survey literature are not easily applied because of complications due to unequal probability sampling. This brief note presents a general proof that the estimator is unbiased for cluster-correlated data regardless of the setting. The result is not new, but a simple and general reference is not readily available. The use of the method will benefit from a general explanation of its wide applicability.