Insomnia and role impairment in the community : results from the Nigerian survey of mental health and wellbeing.

BACKGROUND: Estimates of the occurrence of insomnia are not available in sub-Sahara Africa where demographic profile is different from that in developed countries. However, such estimates need to be considered along with associated functional role impairment in assessing the extent of public health burden due to insomnia.
METHODS: Face-to-face interviews with a representative sample of persons aged 18 years and over (n = 6,752) in 21 of Nigeria's 36 states (representing about 57% of the national population) was conducted using the Composite International Diagnostic Interview, version 3. Role impairment, defined as proportion of lost work over the prior month, was assessed using the World Health Organization's Disability Assessment Schedule.
RESULTS: Insomnia, defined as any sleep complaint lasting at least two weeks in the previous 12-months, was reported by 11.8%, with rates varying between 5.4% for early morning awakening, 7.7% for difficulty initiating sleep, and 8.5% for difficulty maintaining sleep. Increasing age was associated with higher rates of every type of insomnia but females were only more likely than males to report difficulty initiating sleep. Independently, chronic pain conditions, chronic medical conditions, as well as the presence of a DSM-IV mental disorder significantly increased the risk of having insomnia. Multivariate analysis suggests that, even though demographic factors and comorbid physical and mental conditions partly accounted for the association of insomnia with role impairment, a decrement of about 6% of estimated lost work in the prior month was probably attributable to insomnia.
CONCLUSIONS: Findings indicate that insomnia is common even in this relatively young population. Its negative effect on role functioning is considerable, is not entirely accounted for by comorbid medical and mental conditions, and may be of public health significance.