Obstructive Sleep Apnea and Metabolic Health
Condition: Sleep; Apnea; Metabolism Disorder
MeSH terms: Apnea; Metabolic Diseases
Study type: Observational

Summary: 
      This is an observational study involving chart review of patients seen in the bariatric
      clinic since 2012 at The Ohio State University (OSU). Obese patients will be divided into two
      groups according to their metabolic profile (healthy vs unhealthy). The assignment to each
      group will be determined by the presence of diagnosis of hypertension, diabetes mellitus
      and/or dyslipidemia. The presence of at least 2 diagnoses will be defined as metabolically
      unhealthy. Then, each group will be divided based on the presence of Obstructive Sleep Apnea
      diagnosis. All data will be collected through a review of the patient's electronic medical
      record from the bariatric clinic database (the investigators will collect variables as age,
      gender, race, BMI, smoking status, the presence of diagnosis as Obstructive sleep apnea,
      hypertension, diabetes, hyperlipidemia). The investigators will analyze that data and
      establish if there is any correlation between sleep apnea and the subjects' metabolic
      profile.
    

Detailed description: 
      Obesity is associated with numerous metabolic complications including Type 2 diabetes
      mellitus, hypertension, dyslipidemia, cardiovascular disease (CVD) and several forms of
      cancer. However, the presence of these obesity-related metabolic abnormalities varies among
      obese individuals. The phenotype of a metabolically healthy obese (MHO) individual was
      initially described in 1980 and includes a subset of obese patients (as defined by BMI) who
      do not manifest the typical metabolic abnormalities associated with obesity. Although results
      are conflicting and highly dependent on patient population and diagnostic criteria for
      metabolic health, these individuals tend to have a preserved level of insulin sensitivity,
      absence of hypertension, and a more favorable lipid, inflammatory, hormonal, hepatic, and
      immunologic profile compared to the majority of metabolically abnormal obese (MAO) patients.
      This seeming paradox underscores that excess body the weight is not the sole determinant of
      obesity-related complications and allows for novel pathogenic investigation.

      The postulated mechanism(s) underlying the differential metabolic profile in these
      individuals is not well known and the physiologic and molecular basis for 'healthy' obesity
      remains relatively undiscovered. In addition, a recent meta-analysis demonstrated that
      although MHO patients have a comparable metabolic profile to normal the weight individuals,
      their risk of adverse, long-term CV and mortality outcomes remains higher, calling into
      question the clinical importance of the healthy obese categorization. Despite these knowledge
      gaps, a limited number of studies have recently attempted to elucidate the processes that
      lead to the MHO profile, including characterization of lifestyle factors, adipocyte size,
      amount and location of ectopic fat, inflammatory mediators, and immune cells, and differences
      in gene expression.

      The prevalence of obstructive sleep apnea (OSA) increases with increasing BMI and has also
      been linked to various cardiometabolic abnormalities. Patients with OSA experience repetitive
      episodes of hypoxia and reoxygenation during transient cessation of breathing that may
      provoke adverse systemic effects. These effects are reflected in increased levels of
      biomarkers linked to endocrine-metabolic and cardiovascular disease. OSA may exert negative
      effects on the cardiovascular system through multiple mechanisms including hypoxemia, sleep
      disruption, activation of the sympathetic nervous system, and inflammatory activation. In
      spite of this connection, the contribution of these deleterious effects in determining the
      phenotype of an obese patient (MHO vs. MAO) is unknown. Furthermore, the prevalence of OSA in
      these two subsets is not the well established.

      In this study, the investigators hypothesize the prevalence of OSA is higher in MAO compared
      to BMI-matched MAO patients

      Aim 1:

      Define the prevalence of OSA in metabolically-healthy obese and metabolically abnormal obese
      (MHO and MAO) patients.

      Aim 2:

      Elucidate the association of OSA disease severity parameters with markers of clinically
      available abnormal metabolic profile (elevated cholesterol, blood pressure, fasting
      glucose/hemoglobin A1c, inflammatory markers, and insulin resistance if available).
    

Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        The study population will include a representative sample of the patient population at OSU,
        which is 59% Caucasian, 39% African American, and the remainder of mixed, Asian, or Native
        American descent. The investigators will review outpatient data from subjects seen at OSU
        Wexner Medical Center for Minimally Invasive surgery. The individual cohorts will then be
        divided based on the presence of OSA and metabolic abnormalities.