380 Sleep-Wake Disorders
airway. With growth of the airway and regression of lymphoid tissue during later child-
hood, there is reduction in prevalence. Then, as obesity prevalence increases in midlife and
females enter menopause, obstructive sleep apnea hypopnea again increases. The course
in older age is unclear; the disorder may level off after age 65 years, but in other individ-
uals, prevalence may increase with aging. Beca use there is some age dependency of the oc-
currence of apneas and hypopneas, polysomnog raphic results must be interpreted in light
of other clinical data. In particular, signific ant clinical symptoms of insomnia or hyper-
somnia should be investigated re gardless of the individual’s age.
Obstructive sleep apnea hypopnea usually ha s an insidious onset, gradual progression,
and persistent course. Typically the loud snorin g has been present for many years, often since
childhood, but an increase in its severity may lead the individual to seek evaluation. Weight
gain may precipitate an increase in sympto ms. Although obstructive sleep apnea hypopnea
can occur at any age, it most commonly mani fests among individuals ages 40–60 years. Over
4–5 years, the average apnea hypo pnea index increases in adults and older individuals by ap-
proximately two apneas/hypopneas per hour. Th e apnea hypopnea index is increased and in-
cident obstructive sleep apnea hypopnea is greater among indivi duals who are older, who are
male, or who have a higher baseline body mass  index (BMI) or increa se their BMI over time.
Spontaneous resolution of obstructive sleep ap nea hypopnea has been reported with weight