Demographic features of Japanese patients with sporadic inclusion body myositis: a single-center referral experience.
OBJECTIVE
The incidence of sporadic inclusion body myositis (sIBM) in the Japanese population has increased, and some researchers have suggested that race and genetic background may influence the clinical features of the disease. The aim of this study was to clarify the demographic features of Japanese patients with sIBM.


METHODS
We retrospectively evaluated the demographic features of consecutive patients who were referred to our institution between 1995 and 2011 for diagnostic muscle biopsies and who subsequently were diagnosed to have sIBM.


RESULTS
Seventy-three patients comprising 54 men and 19 women received a diagnosis of sIBM during the study period. The patients were divided into two groups based on the date of diagnosis (before and including 2002, and after 2002). The annual number of patients who received a diagnosis of sIBM increased significantly from 3.6±1.6 (mean ± SD) before and including 2002 to 4.9±3.1 (mean ± SD) after 2002 (p<0.05), whereas the annual number of patients who received a diagnosis of polymyositis (PM) or dermatomyositis (DM) remained consistent from 1995 to 2011. The ratio of PM and DM to sIBM was 7.6 during the period from 1995 to 2002 and 5.5 during the period from 2003 to 2011. However, the age-adjusted annual number of patients newly diagnosed with sIBM did not increase significantly after 2002.


CONCLUSIONS
The number of Japanese patients with sIBM appears to have increased in recent years; however, the characteristics of the patients have not changed. Considering the increased size of the elderly population, prolonged lifespans could explain the demographic movement of sIBM in Japan.
Department of Neurology, Nagoya University Graduate School of Medicine, Japan.
Hirotaka
H
Nakanishi
Haruki
H
Koike
Koji
K
Matsuo
Fumiaki
F
Tanaka
Tomoko
T
Noda
Akifumi
A
Fujikake
Seigo
S
Kimura
Masahisa
M
Katsuno
Manabu
M
Doyu
Hirohisa
H
Watanabe
Gen
G
Sobue
D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D001706:Biopsy; D003882:Dermatomyositis / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology; D018979:Myositis, Inclusion Body / Q000175:diagnosis / Q000453:epidemiology*; D017285:Polymyositis / Q000175:diagnosis / Q000453:epidemiology; D012017:Referral and Consultation; D012189:Retrospective Studies