Biomedical subjects

Donald Hedeker

Publications and source records attributed to Donald Hedeker.

8 recordsLinked to original sources

PubMed2005

A mixed-effects quintile-stratified propensity adjustment for effectiveness analyses of ordered categorical doses.

Observational studies can be used to evaluate treatment effectiveness among patients with a broader range of illness severity than typically seen in randomized controlled clinical trials. However, there are several difficulties with observational evaluations including non-equivalent comparison groups, treatment doses and durations that vary widely, and, in longitudinal studies, multiple courses of treatment per subject. A mixed-effects approach to the propensity adjustment for non-equivalent comparison groups is described that can account for each of these perturbations. The strategy involves two stages. First, characteristics that distinguish among subjects who receive various levels of treatment are examined in a model of propensity for treatment intensity using mixed-effects ordinal logistic regression. Second, the propensity-stratified effectiveness of ordered categorical doses is compared in a mixed-effects grouped time survival model of time until recovery. The model is applied in a longitudinal, observational study of antidepressant effectiveness. Then a Monte Carlo simulation study indicates that the strategy has acceptable type I error rates and minimal bias in the estimates of treatment effectiveness. Statistical power exceeds 0.90 for an odds ratio of 1.5 with N = 250 and 500, and is acceptable for an odds ratio of 2.0 with N = 100. Nevertheless, with N = 100, the models that had high intraclass correlation coefficients had greater tendency towards non-convergence. This approach is a useful strategy for observational studies of treatment effectiveness. It is capable of adjusting for selection bias, incorporating multiple observations per subject, and comparing effectiveness of ordinal doses.

Antidepressive Agents↗

PubMed2005

Adherence across behavioral domains in treatment promoting smoking cessation plus weight control.

The authors tested whether adherence to simultaneous health behavior changes was unitary or domain specific among 76 women who modified smoking, eating, and physical activity to accomplish smoking cessation plus weight control. Random-effects regression analyses showed that adherence to both smoking and diet plans declined linearly and covaried positively; their association tended to grow stronger over time. In contrast, physical activity plan adherence did not change over time and was unrelated to other domains. At the end of treatment, 65%, 30.5%, and 25% adhered well or excellently to smoking, diet, and activity treatments, respectively. Findings support both unitary and domain-specific aspects of adherence and suggest that among smokers, smoking and eating behaviors may have similarities unshared by physical activity.

Adult↗

PubMed2005

Effects of acute tryptophan depletion on negative symptoms and smoking topography in nicotine-dependent schizophrenics and nonpsychiatric controls.

We studied the effect of acute tryptophan depletion (ATD), which transiently reduces brain serotonin, on negative symptoms and cigarette smoking topography in schizophrenic smokers. Nicotine-dependent schizophrenics (n=11) and nonpsychiatric controls (n=8) were examined after ingesting comparable mixtures that do and do not deplete plasma tryptophan. Tryptophan-depleting and placebo mixtures were administered double-blind and in counterbalanced order. Conditions were separated by a 1-week interval. Psychopathologic symptoms (negative symptoms, depression) and smoking topography (time to first puff, number of puffs per cigarette, puff duration, interpuff interval, cigarette duration, and percentage of cigarette smoked) were measured before ingestion and again beginning 5 h after each mixture, corresponding to the time of maximal tryptophan depletion. Analyses were conducted using repeated measures analyses of variance (psychopathologic symptoms) and analyses of covariance (smoking topography) controlling for cigarette length. We found that ATD influenced smoking topography in both schizophrenics and nonpsychiatric controls in a manner suggestive of increased desire to smoke. Schizophrenics exhibited increased puff duration and decreased cigarette duration. Controls displayed increased puff duration. ATD did not produce changes in negative symptoms or depression. Compromising brain serotonin via ATD appears to intensify smoking behavior in nicotine-dependent individuals directly, rather than indirectly through changes in either mood or psychopathologic symptoms.

Adult↗

PubMed2004

Hedonic capacity, cigarette craving, and diminished positive mood.

Cigarette craving has been linked to elevated negative and positive moods, but a connection to deficient positive affect has not been studied. We tested whether a low hedonic capacity predicts a heightened urge to smoke after acute nicotine deprivation, and whether such an effect is mediated by decreased positive mood or increased negative mood. A total of 35 smokers characterized for individual differences in hedonic capacity were deprived of nicotine for 48 hr. Using mixed-effects regression modeling, we found that lower hedonic capacity predicted greater increases in craving 24 hr after nicotine withdrawal, t(29)=-2.33, p=.03. The effect of hedonic capacity on increased 24-hr postquit craving to smoke was fully mediated by decreased positive affect. Findings suggest that in early nicotine withdrawal, smokers with diminished capacity to experience pleasure have heightened susceptibility to cigarette cravings that arises because of decreased positive mood rather than increased negative mood.

Adolescent↗

PubMed2003

A mixed-effects multinomial logistic regression model.

A mixed-effects multinomial logistic regression model is described for analysis of clustered or longitudinal nominal or ordinal response data. The model is parameterized to allow flexibility in the choice of contrasts used to represent comparisons across the response categories. Estimation is achieved using a maximum marginal likelihood (MML) solution that uses quadrature to numerically integrate over the distribution of random effects. An analysis of a psychiatric data set, in which homeless adults with serious mental illness are repeatedly classified in terms of their living arrangement, is used to illustrate features of the model.

Adult↗

PubMed2003

Altered reward value of carbohydrate snacks for female smokers withdrawn from nicotine.

Discontinuing nicotine intake usually results in weight gain partially due to heightened energy intake from between-meal snacks. This experiment tested the hypothesis that the reinforcing value of palatable carbohydrate-rich snacks increases for female smokers during nicotine deprivation. Eighteen smokers and 18 nonsmokers completed a concurrent-schedules operant computer task on two separate days. Smokers were bioverified abstinent at the second testing. The operant task allowed participants to earn points redeemable for either carbohydrate snacks or money on concurrent variable-ratio schedules of reinforcement. There were five different probabilities of earning points redeemable for snacks (8%, 16%, 25%, 50%, 75%), while the probability of earning points redeemable for money remained fixed at 25%. Reward value of snacks was measured by switch point: the reinforcement ratio at which the effort required to earn snacks exceeded their value to the respondent, as signified by a shift to working for money. Results showed that smokers undergoing nicotine deprivation persisted in working for snacks into leaner reinforcement schedules than nonsmokers (P=.026). Furthermore, nicotine deprivation increased smokers' allocation of effort to earn snack foods relative to their own behavior when smoking (P=.006). Variation in palatability or hunger did not explain these differences in snack reward value. Findings indicate that nicotine deprivation is associated with a heightened reward value of appealing snack foods for female smokers.

Adolescent↗

PubMed2003

Extended telephone counseling for smoking cessation: does content matter?

Telephone counseling is a popular modality for smoking cessation treatment; however, little attention has been paid to evaluating the efficacy of different contents of calls. This study compared 2 types of proactive telephone calls following a group program. Participants were randomized to receive either: (a) basic content, consisting primarily of support; or (b) enhanced content, tailored to the stage of cessation (still smoking, abstinent, or relapsed) and targeting factors hypothesized to be related to success (motivation, self-efficacy, and negative mood). There was a significant interaction between treatment condition and gender. For men, the enhanced condition produced better abstinence rates through 15 months and lower relapse rates. For women, the basic condition was better. History of depression did not interact with condition.

Adult↗

PubMed2002

Multicenter trial of fluoxetine as an adjunct to behavioral smoking cessation treatment.

The authors evaluated the efficacy of fluoxetine hydrochloride (Prozac; Eli Lilly and Company, Indianapolis, IN) as an adjunct to behavioral treatment for smoking cessation. Sixteen sites randomized 989 smokers to 3 dose conditions: 10 weeks of placebo, 30 mg, or 60 mg fluoxetine per day. Smokers received 9 sessions of individualized cognitive-behavioral therapy, and biologically verified 7-day self-reported abstinence follow-ups were conducted at 1, 3, and 6 months posttreatment. Analyses assuming missing data counted as smoking observed no treatment difference in outcomes. Pattern-mixture analysis that estimates treatment effects in the presence of missing data observed enhanced quit rates associated with both the 60-mg and 30-mg doses. Results support a modest, short-term effect of fluoxetine on smoking cessation and consideration of alternative models for handling missing data.

Adult↗