Insomnia did not predict incident hypertension in older adults in the cardiovascular health study.

INSOMNIA IS THE MOST COMMON SLEEP COMPLAINT IN THE UNITED STATES, AND IS ESTIMATED TO AFFECT 10% TO 30% OF AMERICANS. Insomnia is associated with reduced quality of life and may precede depression1,2 but has not clearly been shown to be causally associated with adverse outcomes. In fact, Kripke and colleagues found a reduced mortality rate for those individuals complaining of sleeping difficulty in a 6-year follow-up study.3 Efforts to establish the prevalence, potential consequences and efficacy of treatment of insomnia have been complicated by the subjective nature and variety of its symptoms. There are several characterizations of insomnia in the literature. In addition, the DSM-III-R4 and DSM-IV5 classifications, the Research Diagnostic Criteria for Insomnia Disorder,6 and the International Classification of Sleep Disorders7 include varying criteria for making the diagnosis of insomnia. A recent National Institutes of Health (NIH) Consensus Conference on insomnia concluded, “Insomnia has historically been defined by complaints of disturbed sleep in the presence of adequate opportunity and circumstance for sleep. The disturbance may consist of one or more of three features: (1) difficulty in initiating sleep; (2) difficulty in maintaining sleep; or (3) waking up too early. A fourth characteristic, nonrestorative or poor-quality sleep, has frequently been included in the definition, although there is controversy as to whether individuals with this complaint share similar pathophysiologic mechanisms with the others.”8 The symptom of nonrestorative sleep, as noted by the NIH consensus conference, is particularly nonspecific and prevalent, and is strongly linked to depression.9 The definition used to define insomnia affects its impact; in one study, some definitions of insomnia predicted incident hypertension but others did not.10 While insomnia has not been causally associated with mortality over 6- or 7-year periods,3,11 longitudinal studies of this duration may not be long enough to demonstrate such effects, if they exist. It is possible that investigation of “upstream” events such as hypertension or other prevalent cardiovascular conditions could yield important information about the natural history of insomnia. Indeed, difficulty falling asleep was associated with an increased risk of angina in a cross-sectional study.12 In summary, the relationship between sleep complaints, medical illness, mood disorders, and hypertension is complex, and more work is needed in this area. The NIH has urged specific research efforts to “Apply well-defined diagnostic criteria to assess the prevalence, incidence, and natural history of insomnia and sleep complaints” and to “Assess the effects of insomnia on public health burdens such as premature death and health care costs.”8 An intriguing relationship exists between sleep duration and hypertension. Gangswisch13 demonstrated that short sleep duration predicted hypertension in an 8-year longitudinal analysis of the National Health and Nutrition Examination Survey. In addition, Lauderdale14 found that African Americans (AA) had shorter objectively measured sleep durations than did Caucasians in the Coronary Artery Risk Development in Young Adults study. This association between short sleep duration and hypertension could be one of the mechanisms accounting for the increased prevalence of hypertension and African Americans. The aim of this analysis was to assess the effect of specific components of insomnia on incident hypertension in the Cardiovascular Health Study. We hypothesized that insomnia complaints predict incident hypertension. As hypertension in older adults has been shown to be a risk factor for stroke, heart failure, and death, identifying easily assessable predisposing risk factors remains important. We were particularly interested in relationships between sleep complaints and hypertension in African Americans, since little data is available about this group, and the CHS cohort is enriched with African Americans. Excess cardiovascular morbidity among African Americans likely has many causes, but we hypothesized that sleep complaints could be among the factors contributing to this phenomenon.