May 25, 2014
Psychiatric distress and insomnia symptoms exhibit similar patterning by gender and
socioeconomic position. Prospective evidence indicates a bi-directional relationship
between psychiatric distress and insomnia symptoms so similarities in social patterning
may not be coincidental. Treatment for insomnia can also improve distress outcomes.
We investigate the extent to which the prospective patterning of distress over 20
years is associated with insomnia symptoms over that period.
999 respondents to the Twenty-07 Study had been followed for 20 years from approximately
ages 36–57 (73.2% of the living baseline sample). Psychiatric distress was measured
using the GHQ-12 at baseline and at 20-year follow-up. Gender and social class were
ascertained at baseline. Insomnia symptoms were self-reported approximately every
five years. Latent class analysis was used to classify patterns of insomnia symptoms
over the 20 years. Structural Equation Models were used to assess how much of the
social patterning of distress was associated with insomnia symptoms. Missing data
was addressed with a combination of multiple-imputation and weighting.
Patterns of insomnia symptoms over 20 years were classified as either healthy, episodic,
developing or chronic. Respondents from a manual social class were more likely to
experience episodic, developing or chronic patterns than those from non-manual occupations
but this was mostly explained by baseline psychiatric distress. People in manual occupations
experiencing psychiatric distress however were particularly likely to experience chronic
patterns of insomnia symptoms. Women were more likely to experience a developing pattern
than men, independent of baseline distress. Psychiatric distress was more persistent
over the 20 years for those in manual social classes and this effect disappeared when
adjusting for insomnia symptoms. Irrespective of baseline symptoms, women, and especially
those in a manual social class, were more likely than men to experience distress at
age 57. This overall association for gender, but not the interaction with social class,
was explained after adjusting for insomnia symptoms. Sensitivity analyses supported
Gender and socioeconomic inequalities in psychiatric distress are strongly associated
with inequalities in insomnia symptoms. Treatment of insomnia or measures to promote
healthier sleeping may therefore help alleviate inequalities in psychiatric distress.
Open Access article