Does the Impact of Intensive Lifestyle Intervention on Cardiovascular Disease Risk Vary According to Frailty as Measured via Deficit Accumulation?

BACKGROUND

Individuals are often counseled to use behavioral weight loss strategies to reduce risk for cardiovascular disease (CVD). We examined whether any benefits for CVD risk from weight loss intervention extend uniformly to individuals across a range of underlying health states.

METHODS

The time until first occurrence of a composite of fatal and nonfatal myocardial infarction and stroke, hospitalized angina, or CVD death was analyzed from 8 to 11 years of follow-up of 4,859 adults who were overweight or obese, aged 45-76 years with Type 2 diabetes. Individuals had been randomly assigned to either an intensive lifestyle intervention (ILI) or diabetes support and education (DSE). Participants were grouped by intervention assignment and a frailty index (FI) based on deficit accumulation, ordered from fewer (first tertile) to more (third tertile) deficits.

RESULTS

Baseline FI scores were unrelated to intervention-induced weight losses and increased physical activity. The relative effectiveness of ILI on CVD incidence was inversely related to baseline FI in a graded fashion (p = .01), with relative benefit (hazard ratio = 0.73 [95% CI 0.55,0.98]) for individuals in the first FI tertile to no benefit (hazard ratio = 1.15 [0.94,1.42]) among those in the third FI tertile. This graded relationship was not seen for individuals ordered by age tertile (p = .52), and was stronger among participants aged 45-59 years (three-way interaction p = .04).

CONCLUSIONS

In overweight/obese adults with diabetes, multidomain lifestyle interventions may be most effective in reducing CVD if administered before individuals have accrued many age-related health deficits. However, these exploratory analyses require confirmation by other studies.

CLINICAL TRIAL REGISTRATION

NCT00017953.

Behavioral and Cardiovascular Effects of a Behavioral Weight Loss Program for People Living with HIV

We recently reported that a 12-week internet weight loss program produced greater weight losses than education control in overweight/obese people living with HIV (PLWH) (4.4 kg vs 1.0 kg; p < 0.05). This manuscript presents the changes in diet, physical activity, behavioral strategies, and cardio-metabolic parameters. Participants (N = 40; 21 males, 19 females) were randomly assigned to an internet behavioral weight loss (WT LOSS) program or internet education control (CONTROL) and assessed before and after the 12-week program. Compared to CONTROL, the WT LOSS arm reported greater use of behavioral strategies, decreases in intake (- 681 kcal/day; p = 0.002), modest, non-significant, increases in daily steps (+ 1079 steps/day) and improvements on the Healthy Eating Index. There were no significant effects on cardio-metabolic parameters. The study suggests that a behavioral weight loss program increases the use of behavioral strategies and modestly improves dietary intake and physical activity in PLWH. Further studies with larger sample sizes and longer follow-up are needed.Clinical Trials Registration: NCT02421406.

Diet Quality Index and Health Behavior Index Generated from a Food Liking Survey Explains Variability in Cardiometabolic Factors in Young Adults (P08-027-19)

Objectives

To test the relationship of diet quality and health behavior indexes derived from a validated food liking survey with cardiometabolic health in a convenience sample of non-diabetic patients with diagnosed depression from a psychiatric facility and age-gender matched students from a University setting.

Methods

One hundred six patients and 106 controls (62% female, mean age = 21) completed a 100-item liking survey comprised of foods, beverages, and physical and sedentary activities. Nutritional items were conceptually grouped, weighted and averaged into a Diet Quality Index (DQI). A Healthy Behavior Index (HBI) was the average of the weighted nutritional and physical activity groups. Higher indexes reflected healthier behaviors. Multiple linear regression was used to relate DQI and HBI with blood pressure and fasting insulin, glucose and serum lipids. BMI, biologic sex and patient status were included as covariates. Some serum markers required transformation to approach normal distribution.

Results

From BMI, 4% were underweight, 57% normal, 25% overweight, and 14% obese. The liking survey took minutes for participants to complete and little processing to generate the indexes. The DQI and HBI were internally reliable (α = 0.68–0.69), reflected greater than one dimension (principal component analysis), and were normally distributed. Higher DQI scores were significantly related to higher HDL (standardized β = 0.16, P = 0.019) and lower glucose (β = –0.19, P = 0.005), insulin (β = –0.18, P = 0.005) and diastolic blood pressure (β = –0.32, P < 0.001). Adding physical activity, HBI also was related to glucose (β = –0.19, P = 0.008), triglycerides (β =–0.14, P = 0.04) and insulin (β = –0.18, P = 0.006). Patient status was not a significant independent contributor in the models.

Conclusions

A simple liking survey can produce reliable and valid indexes of diet quality and health behaviors that significantly associated with multiple cardiometabolic risk factors.

Funding Sources

USDA NIFA, Hatch project.

A Randomized Controlled Trial of a Behavioral Weight Loss Program for Human Immunodeficiency Virus-Infected Patients

Obesity compounds the negative health effects of human immunodeficiency virus (HIV) infection. We conducted the first randomized trial of behavioral weight loss for HIV-infected patients (n = 40). Participants randomized to an Internet behavioral weight loss program had greater 12-week weight loss (mean, 4.4 ± 5.4 kg vs 1.0 ± 3.3 kg; P = .02) and improvements in quality of life than controls. Clinical Trials Registration NCT02421406.

Effects of nicotine deprivation and replacement on BOLD-fMRI response to smoking cues as a function of DRD4 VNTR genotype

INTRODUCTION

Reactivity to smoking cues is an important factor in the motivation to smoke and has been associated with the dopamine receptor 4 variable number tandem repeat (DRD4 exon III VNTR) polymorphism. However, little is known about the associated neural mechanisms.

METHODS

Non-treatment-seeking Caucasian smokers completed overnight abstinence and viewed smoking and neutral cues during 2 separate functional magnetic resonance imaging scans while wearing either a nicotine or placebo patch (order randomized) and were genotyped for the DRD4 VNTR. We conducted mixed-effects repeated-measures analyses of variance (within-subject factor: nicotine or placebo patch; between-subject factor: DRD4 long [L: ≥ 1 copy of ≥ 7 repeats] or short [S: 2 copies ≤ 6 repeats] genotype) of 6 a priori regions of interest.

RESULTS

Relative to neutral cues, smoking cues elicited greater activity in bilateral ventral striatum and left amygdala during nicotine replacement and deactivation in these regions during nicotine deprivation. A patch × DRD4 interaction was observed in the left amygdala, an area associated with appetitive reinforcement and relapse risk, such that S allele carriers demonstrated greater activation on active patch than on placebo patch.

CONCLUSIONS

Brain systems associated with reward salience may become primed and overreactive at nicotine replacement doses intended for the first step of smoking cessation and may become inhibited during nicotine withdrawal in DRD4 S but not in DRD4 L carriers. These findings are consistent with the role of these regions in drug reinforcement and suggest a differential influence of nicotine replacement on amygdala activation in the association of incentive salience with smoking stimuli across DRD4 genotypes.

TCF7L2 polymorphism and cognitive test performance in cardiovascular disease

AIMS

The present study examines cognitive function among transcription factor 7-like 2 (TCF7L2) genotype groups in a sample of older adults with cardiovascular disease.

METHODS

We recruited 111 older adults with diagnosed cardiovascular disease from outpatient cardiology clinics. Neuropsychological tests assessed the following domains of cognitive functioning: global function, attention/executive/psychomotor speed, learning and memory, visuospatial/construction, motor, and language. Genotyping of TCF7L2 single nucleotide polymorphism rs7903146 was conducted to determine membership in the TT, CT, or CC genotype groups.

RESULTS

Controlling for diabetes status, participants with the TT genotype of TCF7L2 (n= 12) performed worse on tests of attention/executive function/processing speed than those with the CC (n= 46) and CT (n= 53) genotypes, despite no between-group differences in demographic or medical variables.

CONCLUSIONS

Older cardiovascular disease patients with the TCF7L2 TT genotype performed worse on tests of attention/executive/ psychomotor speed than CC and CT genotype carriers. Further work using neuroimaging and glucose tolerance indices is needed to clarify underlying mechanisms.

Large-scale gene-centric meta-analysis across 39 studies identifies type 2 diabetes loci

To identify genetic factors contributing to type 2 diabetes (T2D), we performed large-scale meta-analyses by using a custom ∼50,000 SNP genotyping array (the ITMAT-Broad-CARe array) with ∼2000 candidate genes in 39 multiethnic population-based studies, case-control studies, and clinical trials totaling 17,418 cases and 70,298 controls. First, meta-analysis of 25 studies comprising 14,073 cases and 57,489 controls of European descent confirmed eight established T2D loci at genome-wide significance. In silico follow-up analysis of putative association signals found in independent genome-wide association studies (including 8,130 cases and 38,987 controls) performed by the DIAGRAM consortium identified a T2D locus at genome-wide significance (GATAD2A/CILP2/PBX4; p = 5.7 × 10(-9)) and two loci exceeding study-wide significance (SREBF1, and TH/INS; p < 2.4 × 10(-6)). Second, meta-analyses of 1,986 cases and 7,695 controls from eight African-American studies identified study-wide-significant (p = 2.4 × 10(-7)) variants in HMGA2 and replicated variants in TCF7L2 (p = 5.1 × 10(-15)). Third, conditional analysis revealed multiple known and novel independent signals within five T2D-associated genes in samples of European ancestry and within HMGA2 in African-American samples. Fourth, a multiethnic meta-analysis of all 39 studies identified T2D-associated variants in BCL2 (p = 2.1 × 10(-8)). Finally, a composite genetic score of SNPs from new and established T2D signals was significantly associated with increased risk of diabetes in African-American, Hispanic, and Asian populations. In summary, large-scale meta-analysis involving a dense gene-centric approach has uncovered additional loci and variants that contribute to T2D risk and suggests substantial overlap of T2D association signals across multiple ethnic groups.

CAMTA1 T polymorphism is associated with neuropsychological test performance in older adults with cardiovascular disease

BACKGROUND

Cardiovascular disease has long been associated with poor neurocognitive outcome, with multiple pathophysiological mechanisms that are linked to cognitive impairment in older adults. Although less frequently examined, insulin dysregulation is known to affect vascular function and the associated brain dysfunction in cardiovascular disease. Accordingly, genetic factors tied to insulin regulation may make certain people with cardiovascular disease more susceptible to cognitive dysfunction. Specifically, the calmodulin-binding transcription activator 1 (CAMTA1) genotype, which has been examined as a risk factor for Type 2 diabetes and has been linked to reduced episodic memory performance in healthy young adults, is a potential candidate gene.

METHODS

Blood samples were obtained from 113 older adults with cardiovascular disease who also underwent neuropsychological testing. Carriers of either one or two copies of the T allele of CAMTA1 were categorized into one group (n = 63), whereas non-carriers were categorized into a second group (n = 50).

RESULTS

Analyses showed that carriers of the T allele performed more poorly on tests of attention, executive function, and psychomotor speed, but not on tests of memory. Carriers of the T allele also performed more poorly on a measure of global cognitive function.

CONCLUSIONS

Results indicate that CAMTA1 genotype is associated with cognitive function in older adults with cardiovascular disease, because carriers of the T allele performed more poorly on tests of attention, executive function, and psychomotor speed. Contrary to expectations, there were no differences in memory performance among carriers and non-carriers of the T allele. Given these mixed findings, further studies are necessary to elucidate the association between CAMTA1 and cognition, particularly gene expression and neuroimaging studies.

A test for common genetic and environmental vulnerability to depression and diabetes

Molecular genetic research has provided some evidence for the association between depression and metabolic disorders. We sought to determine if molecular findings are reflected in twin analyses testing if common genetic and environmental risk factors contribute to the co-occurrence of diabetes and depression. Data to derive depression and diabetes were collected from 1,237 male-male twins who participated in the 2005 Vietnam Era Twin Study of Aging (VETSA). The 1,237 twins were comprised of 347 MZ pairs, 3 MZ singletons, 267 DZ pairs and 6 unpaired twins. Depression was defined as a score below 46 on the Short Form-36 mental component summary score. Diabetes was defined by self report, use of anti-diabetic medications and insulin. Twin models were fit to estimate the correlation of genetic and environmental contributions to depression and diabetes. Consistent with other studies these data support the association between depression and diabetes (OR = 1.7; 95%CI: 1.1-2.7). Genetic vulnerability accounted for 50% (95%CI: 32%-65%) of the variance in risk for depression and 69% (95%CI: 52%-81%) of the variance in risk for diabetes. The genetic correlation between depression and diabetes was r = 0.19 (95%CI: 0-0.46) and the non-shared environmental correlation was r = 0.09 (95% CI: 0-0.45). Overall there is little evidence that common genetic and environmental factors account for the co-occurrence of depression and diabetes in middle aged men. Further research in female twins and larger cohorts is warranted.

Treatment (trx) patterns of angiogenesis inhibitors in patients (pts) with metastatic renal cell carcinoma (mRCC) in Ireland

383

Background: This study evaluated rates of trx modifications and reasons for these changes among pts treated with angiogenesis inhibitors in Irish clinical practice.

Methods: Data from medical records were retrospectively reviewed at 3 large oncology centers in Ireland for mRCC pts who were ≥ 18 years and received sunitinib (SU) (n=54), sorafenib (n=9), bevacizumab (n=6), or temsirolimus (n=7) as first-line trx from 1/1/2005 to 8/31/2010. Proportions of pts with trx discontinuation (d/c), interruption, or dose change, and reasons for modifications and time to modifications were determined.

Results: Due to small sample sizes in other groups, only results for SU are summarized. 1.9% of pts had prior cytokine therapy. Median first-line trx duration for SU was 8.7 months (mo), while median progression-free survival was 13.8 mo. 87% of patients treated with first-line SU experienced adverse events (AEs); 18.5% experienced grade 3/4 AEs. AEs led to trx modifications in 42.6% of pts. 94.4% of pts started trx on 50 mg QD 4/2 dosing; 33.3% of them were dose reduced to 37.5 mg QD 4/2 with median time to reduction 2.7 mo. Among pts who discontinued trx, 31.6% discontinued within 18 weeks (w) (15.8% within 0-6 w, 7.9% in 7-12 w, and 7.9% in 13-18 w). Among pts who discontinued trx within 18 w, 66.7% discontinued due to AEs.

Conclusions: Over three-quarters of SU pts experienced trx modifications, more than half due to AEs. About 24% of txt discontinuations occurred within the first two cycles. This real-world practice study suggests that treatment tolerability is a challenge for physicians in the clinical care of mRCC pts.

[Table: see text]

[Table: see text]

P-selectin 1087G/A polymorphism is associated with neuropsychological test performance in older adults with cardiovascular disease

BACKGROUND AND PURPOSE

There is growing evidence that the cell adhesion molecule P-selectin (SELP) contributes to the adverse vascular processes that promote cognitive impairment in individuals with cardiovascular disease. Previous research has shown that SELP genotypes moderate circulating levels of P-selectin and that patients undergoing coronary artery bypass graft with the SELP 1087A allele were less likely to show postoperative cognitive decline and more likely to exhibit lower levels of C-reactive protein than noncarriers. Thus, we expected that carriers of the 1087A allele (n=43) would exhibit better cognitive functioning than persons with 2 1087G alleles (n=77) and that C-reactive protein levels would be important for this relationship.

METHODS

One hundred twenty older adults with diagnosed cardiovascular disease were recruited from outpatient cardiology clinics. Each participant underwent a comprehensive neuropsychological test battery and a blood draw.

RESULTS

Participants with the SELP 1087A allele performed more poorly on tests of attention (Trail Making Test A: t[116]=3.20, P=0.002), executive function (Trail Making Test B: t[116]=2.89, P=0.005), psychomotor speed (Digit-Symbol Coding: t[117]=2.54, P=0.012), and memory (California Verbal Learning Test Discrimination: t[116]=2.05, P=0.04). There were no significant differences between the SELP genotype groups on demographic/medical variables or C-reactive protein levels.

CONCLUSIONS

Contrary to expectations, the present analyses showed that older patients with cardiovascular disease with the SELP 1087A allele performed more poorly on neuropsychological testing. Findings from the present study were counter to previous research with coronary artery bypass graft candidates. Further work using neuroimaging and alternative measures of cardiovascular function is needed to clarify the mechanisms of this association.

Maintaining large weight losses: the role of behavioral and psychological factors

Few studies have examined predictors of weight regain after significant weight losses. This prospective study examined behavioral and psychological predictors of weight regain in 261 successful weight losers who completed an 18-month trial of weight regain prevention that compared a control condition with self-regulation interventions delivered face-to-face or via the Internet. Linear mixed effect models were used to examine behavioral and psychological predictors of weight regain, both as main effects and as interactions with treatment group. Decreases in physical activity were related to weight regain across all 3 groups, and increased frequency of self-weighing was equally protective in the 2 intervention groups but not in the control group. Increases in depressive symptoms, disinhibition, and hunger were also related to weight regain in all groups. Although the impact of changes in restraint was greatest in the Internet group and weakest in the face-to-face group, the latter was the only group with increases in restraint over time and consequent decreases in magnitude of weight regain. Future programs should focus on maintaining physical activity, dietary restraints, and frequent self-weighing and should include stronger components to modify psychological parameters.

Association of a serotonin transporter polymorphism (5-HTTLPR) with depression, perceived stress, and norepinephrine in patients with coronary disease: the Heart and Soul Study

OBJECTIVE

The short allele of a functional polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) has been shown to interact with stressful life events to predict depression in otherwise healthy individuals. Whether the short allele increases risk for depression associated with the stress of a chronic illness has not been established.

METHOD

In a cross-sectional genetic association study, the authors examined the association of 5-HTTLPR with current depression (measured by the Computerized Diagnostic Interview Schedule), perceived stress (measured by the Perceived Stress Scale), and 24-hour urinary norepinephrine excretion in 557 outpatients with chronic coronary disease.

RESULTS

Among individuals carrying an s allele, 25% (97 of 383) had current depression, compared with 17% (29 of 174) of l/l homozygotes. The unadjusted odds ratio was 1.6, with a 95% confidence interval (CI) of 1.0-2.6; the age- and gender-adjusted odds ratio was also 1.6 (95% CI=1.0-2.5). Participants carrying an s allele had a higher mean score for perceived stress than l/l homozygotes (5.4 versus 4.7) and a higher rate of moderate or high perceived stress (adjusted odds ratio=1.6, 95% CI=1.1-2.3). Mean 24-hour norepinephrine excretion was higher in s allele carriers (55.6 versus 50.2 mg/day), who were more likely to have norepinephrine values in the highest quartile (adjusted odds ratio=1.7, 95% CI=1.0-3.0).

CONCLUSIONS

Among patients with chronic illness, carriers of the s allele of 5-HTTLPR are more vulnerable to depression, perceived stress, and high norepinephrine secretion. These factors may contribute to worse cardiovascular outcomes in these patients.

Pharmacogenetic clinical trial of sustained-release bupropion for smoking cessation

This randomized, double-blinded, placebo-controlled trial examined genetic influences on treatment response to sustained-release bupropion for smoking cessation. Smokers of European ancestry (N = 291), who were randomized to receive bupropion or placebo (12 weeks) plus counseling, were genotyped for the dopamine D2 receptor (DRD2-Taq1A), dopamine transporter (SLC6A3 3' VNTR), and cytochrome P450 2B6 (CYP2B6 1459 CT) polymorphisms. Main outcome measures were cotinine-verified point prevalence of abstinence at end of treatment and at 2-, 6-, and 12-month follow-ups post quit date. Using generalized estimating equations, we found that bupropion, compared with placebo, was associated with significantly greater odds of abstinence at all time points (all p values<.01). We found a significant DRD2 x bupropion interaction (B = 1.49, SE = 0.59, p = .012) [corrected] and a three-way DRD2 x bupropion x craving interaction on 6-month smoking cessation outcomes (B = -0.45, SE = 0.22, p = .038), such that smokers with the A2/A2 genotype demonstrated the greatest craving reduction and the highest abstinence rates with bupropion. Furthermore, there was a significant DRD2 x CYP2B6 interaction (B = 1.43, SE = 0.56, p = .01), such that individuals with the DRD2-Taq1 A2/A2 genotype demonstrated a higher odds of abstinence only if they possessed the CYP2B6 1459 T/T or C/T genotype. Because the sample size of this study was modest for pharmacogenetic investigations, the results should be interpreted with caution. Although these results require replication, the data suggest preliminarily that the DRD2-Taq1A polymorphism may influence treatment response to bupropion for smoking cessation and, further, that exploration of gene x gene and gene x craving interactions in future, larger studies may provide mechanistic insights into the complex pharmacodynamics of bupropion.

Early life stress and adult emotional experience: an international perspective

Early life stress (ELS) has been linked to adult psychopathology, though few studies have examined the universality of specific adverse childhood events (ACEs) in healthy adults. We examined the co-occurrence of specific ACEs and their relationship to current emotional distress in an international sample of adults without psychopathology. Participants were 1659 men and women recruited for an international neurocognitive-neuroimaging database from sites in the United States, Australia, England, and the Netherlands. Participants had no current or prior diagnosis of major depression, anxiety, substance abuse, or neurological brain disorder. The occurrence and age on onset of 19 ACEs was assessed by a self-report questionnaire (ELSQ), and current symptoms of stress, depression, and anxiety by the Depression Anxiety Stress Scale (DASS). The relationship of specific ACEs to DASS symptoms was examined. Participants reported relatively high prevalence of ACEs. Only 27.6% of the sample reported no ACEs, while 39.5% reported one or two significant experiences and 32.9% reported more than two ACEs. Rates of most ACEs were quite similar across the three continents. Various ACEs were significantly associated with current DASS severity, particularly ACEs involving emotional abuse, neglect, and family conflict, violence, and breakup. Finding nearly one-third of the sample reported three or more ACEs suggest a high prevalence of ELS in otherwise healthy "normal" adults around the world. Associations between ELS and current emotional distress suggest that these events have functional relevance and deserve further investigation.

Community socioeconomic status is associated with carotid artery atherosclerosis in untreated, hypertensive men

BACKGROUND

Individuals of low socioeconomic status (SES) are at increased risk for cardiovascular disease relative to persons of more advantaged social position. Recent evidence suggests that community SES (variation in the material and social resources of communities) also predicts incident cardiovascular disease, and may do so independently of individual level SES. In this study we examined whether community SES is similarly associated with preclinical vascular disease, as measured by carotid artery ultrasonography.

METHODS

Subjects were 230 untreated hypertensive men without history of coronary heart disease, residing in and around Pittsburgh, PA (80% white, 20% African-American; mean age, 56 years). Community SES was defined by levels of income, economic disadvantage (eg, poverty, unemployment), housing costs, and educational attainment in the US Census tract of residence for each subject. A composite community SES score was calculated for each subject as the average of all extracted census measures. Individual SES was estimated from subjects' years of education and current annual income.

RESULTS

Regression analyses accounting for traditional risk factors showed community disadvantage to be associated with greater intima-medial thickness (b = 0.02, P < .05) and plaque occurrence (odds ratio [OR] = 1.51, P < .01). The latter association persisted on multivariable adjustment for both risk factors and individual markers of social position (SES) (OR = 1.68, P < .01).

CONCLUSIONS

Irrespective of one's own income or educational attainment, untreated hypertensive men living in poorer communities are more likely to exhibit preclinical atherosclerosis than residents of more affluent areas.

Early life stress and morphometry of the adult anterior cingulate cortex and caudate nuclei

BACKGROUND

Early life stress (ELS) is linked to adult psychopathology and may contribute to long-term brain alterations, as suggested by studies of women who suffered childhood sexual abuse. We examine whether reported adverse ELS defined as stressful and/or traumatic adverse childhood events (ACEs) is associated with smaller limbic and basal ganglia volumes.

METHOD

265 healthy Australian men and women without psychopathology or brain disorders were studied. ACEs were assessed by the ELSQ and current emotional state by the DASS. Anterior cingulate cortex (ACC), hippocampus, amygdala, and caudate nucleus volumes were measured from T1-weighted MRI. Analyses examined ROI volumetric associations with reported ACEs and DASS scores.

RESULTS

Participants with greater than two ACEs had smaller ACC and caudate nuclei than those without ACEs. A significant association between total ACEs and ROI volumes for these structures was observed. Regression analysis also revealed that ELS was more strongly associated than current emotional state (DASS) with these ROI volumes.

CONCLUSIONS

Reported ELS is associated with smaller ACC and caudate volumes, but not the hippocampal or amygdala volumes. The reasons for these brain effects are not entirely clear, but may reflect the influence of early stress and traumatic events on the developing brain.

A twin-sibling study of tobacco use in adolescence: etiology of individual differences and extreme scores

A database is emerging that examines the relative contributions of genes and the environment to the etiology of smoking in adolescence. We present analyses derived from a genetically informative subsample of sibling pairs (monozygotic and dizygotic twins, full siblings, and half-siblings) participating in two waves of the National Longitudinal Study of Adolescent Health to estimate these parameters on both individual differences in smoking and extreme levels of smoking. Evidence indicated both genetic and shared environmental influences on high levels of smoking frequency, as well as on individual differences in smoking. No notable gender differences in these parameters emerged. Shared environmental effects were especially notable for high levels of smoking frequency and significantly greater than those found for individual differences. These findings were compatible with prior studies of both adolescent and adult smoking and reinforce the importance of familial influences on high levels of smoking frequency in adolescence.

Posttraumatic stress disorder and late-onset smoking in the Vietnam era twin registry

Epidemiological and clinical studies have consistently reported associations between smoking and posttraumatic stress disorder (PTSD). This study analyzed diagnostic interview data on 6,744 members of the Vietnam Era Twin Registry to clarify the PTSD-smoking relation and to examine whether genetic liability for smoking moderated this relation. Preexisting active (unremitted) PTSD increased risk of late-onset daily smoking. Remitted PTSD decreased risk. Active PTSD increased risk of smoking at all levels of genetic liability; the effect was strongest for those with least genetic liability. This suggests PTSD represents a nongenetic pathway to late-onset smoking among individuals who were nonsmokers prior to developing PTSD. If replicated, these results identify PTSD as a risk factor for smoking that should lead to early tobacco control treatment in this population.

A twin registry study of the relationship between posttraumatic stress disorder and nicotine dependence in men

CONTEXT

Recent studies indicate a strong association between posttraumatic stress disorder (PTSD) and nicotine dependence (ND). However, the explanation for the association remains unclear.

OBJECTIVE

To test competing explanations for the association between PTSD and ND.

DESIGN, SETTING, AND PARTICIPANTS

Analysis of data on 6744 members of the Vietnam Era Twin Registry, a national registry of all male-male twin pairs who served in the military during the Vietnam era interviewed in 1991-1992.

MAIN OUTCOME MEASURES

Risk of PTSD and ND using the Diagnostic Interview Schedule for the DSM-III-R.

RESULTS

The prevalence of ND was elevated among trauma-exposed individuals (52.0%) and those with PTSD (71.7%) compared with unexposed individuals (40.5%). This association was significant for ND and for trauma without PTSD (odds ratio, 1.31; 95% confidence interval [CI], 1.18-1.45) and for PTSD (odds ratio, 2.34; 95% CI, 1.92-2.84) and was not entirely explained by shared risk factors. Shared genetic effects explained 63% of the PTSD-ND association; the remaining covariance was explained by individual-specific environmental effects. Using survival analysis with time-dependent covariates, ND was associated with a substantially increased risk of PTSD among trauma-exposed men (hazard ratio, 1.98; 95% CI, 1.61-2.42). Trauma (hazard ratio, 1.49; 95% CI, 1.35-1.64) and PTSD (hazard ratio, 1.36; 95% CI, 1.14-1.61) were less strongly but significantly associated with increased risk of ND onset after controlling for shared risk factors.

CONCLUSIONS

Most of the PTSD-ND association is explained by shared genetic effects. However, there is a substantial, robust PTSD-ND association not explained by shared risk factors. Multiple explanations for the association were supported; however, the strongest association was consistent with preexisting ND increasing the risk of PTSD onset. These data suggest that male veterans with a history of ND may be at increased risk for PTSD. Further research on the biological mechanisms underlying PTSD-ND comorbidity is needed.

Differential satiating effects of fats in the small intestine of obesity-resistant and obesity-prone rats

The effects of duodenal infusions of fats on sham feeding was measured in two strains of rats that differ in their susceptibility to fat-induced obesity. Osborne-Mendel rats are prone to developing obesity on a high-fat diet and preferentially choose fats over carbohydrates in macronutrient selection paradigms. In contrast, S 5B/PL rats are resistant to developing obesity when eating a high-fat diet, and preferentially choose carbohydrates in macronutrient selection paradigms. To test the hypothesis that differences in the satiating potency of fats in the small intestine contributed to these differences between the two strains, we measured the effects of duodenal infusions of Intralipid and sodium linoleate on sham-feeding intakes. The results were consistent with the hypothesis. Duodenal infusions of either of these fats decreased intake significantly more in S5B/PL rats than in Osborne-Mendel rats. Both rat strains sham fed similar amounts when intestinally infused with 0.15 M NaCl. These results suggest that differences in responses to intestinal satiating mechanisms may contribute to the differences in susceptibility to fat-induced obesity in these rat strains.