Research Article CritiqueKayla Muth

Article Overview Title

Prospective Study of Obstructive Sleep Apnea and Incident Coronary Heart Disease and Heart Failure: The Sleep Heart Health Study

Study began in 1994 and ended in 2006

Submitted August 2009

Accepted May 2010

Published in Circulation July 2010

Sources Publication dates ranged from 1975-2009

Selection of Journals and Studies American Journal of Cardiology American Journal of Medicine Circulation Framingham Heart Study Journal of the American Medical Association Journal of Applied Physiology New England Journal of Medicine Sleep

Definitions Obstructive Sleep Apnea (OSA)

Continuous Positive Airway Pressure Therapy

Community Based Prospective Cohort Study

Polysomnography

Electroencephalogram

Electrooculogram

Chin electromyogram

Inductance plethysmography

Apnea

Hypopnea

Apnea-hypopnea index (AHI)

Incident CHD

Incident Heart Failure

Cox proportional hazards regression modeling

Linear regression splines

LOWESS

Adjusted hazard ratio

Purpose of the Study “To assess the independent contribution of

OSA to cardiovascular disease, the Sleep Heart Health Study (SHHS) was initiated in 1994 as a multicenter, prospective cohort study of the cardiovascular consequences of OSA.”

“The present report details the incidence of CHD and heart failure in SHHS participants free of these conditions at the baseline examination.”

Study Design Adults 40 years of age and older were recruited

from existing population-based studies of cardiovascular and pulmonary disease

Participants completed questionnaires on sleep habits and general health

Height, weight, and blood pressure were measured

Underwent overnight polysomnography

Parent cohorts provided data

Ongoing surveillance for cardiovascular disease through April 2006

Study Sample 10,737 cohort participants invited to participate

6,441 were enrolled in study 760 participants from NYU-Cornell site excluded 783 participants excluded due to prevalent heart

disease or heart failure at baseline 21 participants lacked follow-up data and were

excluded 455 participants were missing baseline measures and

excluded

4,422 subjects remained for participation 2,495 females 1,927 males

Methods In-home polysomnography

Polysomnograms scored centrally and AHI determined

Ongoing surveillance for CHD and heart failure by parent-cohorts

Follow-up procedures performed by cohorts Median follow-up ranged from 8.3-9.2 years

All CHD and heart failure outcomes extracted from hospital and physician’s records by trained abstractors

~5 years post-baseline, survey relative to diagnosis of and treatment for OSA completed by 3,794 participants

Covariates Baseline prevalent CHD or

heart failure

Smoking status

Medication

Diabetes

Blood pressure

Weight

Race/ethnicity

Height

Total cholesterol

HDL cholesterol

Statistical Analysis Performed with SAS version 9.2

Descriptive statistics presented by category of OSA severity based on the AHI

Testing for improved model fit Cubic or quadratic functions Linear regression splines LOWESS

Association between sex and AHI Models created for males and females

Statistical Analysis cont.

Models using AHI as continuous dependent variable adjusted for the following independent variables: (1) Age, race, BMI, and smoking status (2) Variables from model (1) plus total and HDL

cholesterol and diabetes (3) Variables from model (2) plus hypertension

Models repeated using parent cohort instead of race

Models constructed to stratify age >70 years old ≤ 70 years old

Results Increasing severity with OSA was associated with

male sex, higher BMI, higher systolic blood pressure, lower HDL cholesterol, and higher prevalence of hypertension and diabetes

Median AHI in women was 2.7 (interquartile range 0.8 to 7.5) and 6.2 in men (interquartile range 2.3 to 14.3)

During follow-up period there were 473 incident CHD events 76 CHD deaths 185 MI’s 212 revascularization procedures

Results cont. During follow-up there were 308 incidents of

heart failure; 144 also had incident CHD

Rate of events increased with severity of OSA in men, but not as clearly in women

When adjusted for age, race, BMI, and smoking status there was a significant association between AHI with incident CHD in men

Discussion This study found an association between

incident CHD and OSA in men that was considerably weaker than previous clinic-based studies

Screening of non-clinic-based population identified many asymptomatic individuals with OSA

SHHS may underestimate the true cardiovascular risk associated with OSA due to median age of 62

Study demonstrates a 58% higher adjusted risk for incident heart failure for men with OSA

Strengths Community-based recruiting limited referral

bias

Detailed covariate data

Exclusion criteria provided

Few received treatment for OSA allowing for assessment of natural history of untreated OSA

Includes both men and women

Ethnically diverse

Weaknesses Older age of the cohort

Echocardiograms were not routinely performed

Varying protocols at different facilities

Varying frequency of follow-ups

Authors do not appear to be individuals who extracted data from medical records

BMI is imperfect way to collect anthropometric data

Diet and exercise not recorded

Significance Potentially significant because it does

suggest an increased risk of incident heart failure in those with OSA

Those with OSA tend to have all other risk factors predisposing them to heart disease, so it is hard to demonstrate if OSA has significant impact independent of those risk factors