Insomnia has a pervasive influence on daily life
functions compromising social and occupational
performance5–8). Moreover, the prevalence of insomnia
has been found to be associated with various medical
conditions (e.g. musculoskeletal disease, digestive
disease, circulatory disease, respiratory disease, diabetes
and migraine)9–12). We previously elucidated
sociodemographic, lifestyle, psychological and physical
factors associated with two subtypes of insomnia in
Japanese male workers. After adjusting for confounding
factors, difficulty initiating sleep (DIS) and difficulty
maintaining sleep (DMS) were significantly associated
with hypertension (HT)13, 14). Similarly, several
investigators reported a significant association between
insomnia and HT9, 12), but these findings were derived
from cross-sectional analyses. There has been insufficient
evidence to answer the question whether insomnia leads
to HT or vice versa.
HT is one of the most important health problem in
Japan15). A better understanding of the association
between insomnia and HT will afford a new prospect on
measures to prevent HT. In this study, we conducted a 4-
yr follow-up of Japanese male workers to assess the effect
of insomnia on the development of HT.
Methods
A longitudinal database was accumulated from an
employee health management center in a Japanese
telecommunication company. Details of the process of
annual health examination have been described