Purpose: This study compared in one data set the relative importance of most previously examined risk factors for different symptoms of insomnia.
Methods: Data were obtained from personal interviews of 1,588 adults in a rural area. Statistical methods evaluated the association of 42 risk factors with any insomnia and each of four insomnia subtypes: difficulty with initiating sleep (DIS), difficulty maintaining sleep (DMS), early morning awakening (EMA), and restless sleep (RS).
Results: Insomnia rates were greater in this rural population than most U.S. studies and greater in the United States than other countries. The correlations between insomnia subtype and energy level was highest for RS, -0.29, and lowest for EMA, -0.11. All sleep disturbances increased monotonically with depressive symptoms, but the increase was greatest for RS (r = 0.57) and weakest for EMA (r = 0.24). Anxiety and pain also were independently associated with each insomnia subtype. Insomnia problems of spouses were uncorrelated. Other risk factors were independently associated with some insomnia subtypes but not others. For example, the association of age with difficulty maintaining sleep was independent of health measures.
Conclusion: The results suggest that different insomnias have different rates and risk factors and therefore possibly different etiologies and management strategies.