Date of Award

2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Pharmaceutical Sciences

First Advisor

Cynthia Willey

Abstract

Recognizing the substantial public health impact of tobacco dependence (TD) and consequent importance of reducing tobacco use, the United States Public Health Service (USPHS) issues evidence based clinical practice guidelines (CPG) that urge “clinicians and health care delivery systems to consistently identify and document tobacco use status and treat every tobacco user seen in a health care setting”. The latest guidelines, published in 2008, were written “in response to new, effective clinical treatments for tobacco dependence” identified since 1999 and contain strategies and recommendations designed to assist clinicians, administrators, insurers, and purchasers in “delivering and supporting effective treatments for tobacco use and dependence”. The guidelines state that, barring contraindication or insufficient study in a specific sub-group, interventions for tobacco cessation are appropriate for all individuals who use tobacco, including patients with medical co-morbidities. Specific medical co-morbidities cited in the CPG for which pharmacologic interventions have been shown effective include cancer. Moreover, continued smoking in cancer patients can affect the pharmacokinetics of cancer treatments.

An important consideration for patients selected for treatment with smoking cessation medication (SCM) is the duration of therapy or persistence with therapy as these measures of medication adherence have been found to be associated with treatment success in clinical trials. Another important factor to consider in assessing SCM is recognition that tobacco dependence is a chronic disease that often requires repeated interventions. Patient relapse to tobacco use following a period of abstinence achieved with use of SCM is not unexpected.

Since the CPG serve as the definitive source to inform tobacco cessation practice in the US, one would expect that epidemiologic studies of smoking cessation medications (SCM) have been conducted in order to understand intervention use in routine clinical practice, both in the overall population of tobacco dependent patients and those with smoking related co-morbidities, such as cancer since epidemiologic studies are a required early step in the process toward closing gaps in care.

However, literature search for population level studies in large representative populations revealed few and most are derived from survey level data. Similarly, literature search for studies of the use of SCM in patients with cancer returned few results. Thus, real world studies describing the epidemiology of SCM in routine US clinical practice are lacking. Though they are not without limitations, adequately controlled observational studies using administrative healthcare claims data can answer important questions in a relatively inexpensive and time-efficient manner.

This dissertation utilizes the manuscript format and has three main objectives:

  1. To describe the pharmacoepidemiology of SCM among smokers identified through CPT and ICD-9 codes to answer the question, “Who among smokers receives pharmacologic treatment?”
  2. To describe treatment persistence in tobacco dependent patients prescribed SCM, repeat treatment with SCM and patient and prescriber characteristics associated premature discontinuation and repeat therapy.
  3. Evaluation of the use of SCM among tobacco dependent patients with smoking related cancer diagnoses to answer the question, “Who receives pharmacologic treatment and who doesn’t?

The LifeLinkTM Health Plan Claims Database was employed to identify patients diagnosed or counseled for tobacco cessation (index) during a one year period and evaluate the use of SCM in the 1 year following the index date, rates of premature discontinuation and repeat therapy as well as use of SCM in patients with smoking related cancers. Predictors of the use of SCM in tobacco dependent patients, premature discontinuation and repeat therapy were assessed using logistic regression models, controlling for pre-index patient and/or treatment characteristics. The same was performed to identify predictors of SCM use in tobacco dependent patients with smoking related cancer.

Major findings reported in the first manuscript are that approximately 11% of newly diagnosed tobacco dependent patients received treatment within a year of diagnosis and that the youngest and oldest age groups were less likely to receive SCM than those at middle age. Of note, patients who may have had tobacco related co-morbidities were less likely to receive treatment than those without. The study of persistence and repeat therapy revealed that mean persistence was 36 days and that >90% of patients discontinued SCM before 12 weeks of therapy, shorter than recommendations. Patients under 50 years old and 65 years or older were more likely to discontinue prematuredly than patients aged 50-58 years. Few patients (5%) repeated therapy ≥ 26 weeks following index. The final study of the use of SCM in tobacco dependent patients with smoking related cancer revealed that tobacco dependence of counseling/advice for smoking cessation in these patients was likely coincident or following diagnosis of comorbidity. This finding was also noted in the first study where pre-index mean Charlson Comorbidity was lower than the period following diagnosis.

The 3 studies presented provide insight into the utility of using administrative claims data to study patients who are tobacco dependent and their treatment with SCM. Taken in their entirety, these studies’ findings contribute certain apparent overarching themes and other important observations that may be useful to practicing clinicians to highlight potential opportunities for treatment with SCM in patients who may benefit most. First, it seems that the health system is identifying patients as tobacco dependent co-incident with identification of other co-morbidity. Earlier intervention of management of tobacco dependence is likely the best strategy to aid patients in quitting. Second, diagnosis or counseling by a hospital related practitioner was associated with reduced likelihood of SCM treatment as an outpatient overall and in patients with smoking related cancer. Hospitalization has been identified as an opportune time for clinicians to intervene and offer assistance with smoking cessation. Diagnosis by a therapeutic specialist was associated with lower likelihood of SCM use and tobacco dependence can be a major contributor to risk of events often managed by therapeutic area specialists, e.g., cardiologists and oncologists. Rates of treatment with SCM by physician type is not widely described but literature reports and clinical practice guidelines recommend that cardiologists and oncologists are well positioned to assist patients in their quit attempts to reduce overall health risks.

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