The incidence of interstitial lung disease 1995-2005: a Danish nationwide population-based study.
BACKGROUND
Current data on incidence of interstitial lung diseases (ILDs) are sparse and concerns about an increasing trend have been raised. We examined incidence rates (IRs) of ILDs and changes in IRs between 1995 and 2005.


METHODS
All persons with a first-time hospital discharge or outpatient diagnosis of ILD were identified through the Danish National Registry of Patients, which covers all Danish hospitals. Crude and age-standardised IRs were computed for ILD overall, as well as stratified by ILD subcategories.


RESULTS
A total of 21,765 patients with ILD were identified. Between 1995 and 1998 the overall standardised IR of ILD decreased from 27.14 (95% CI 25.82-28.46) per 100,000 person-years to 19.36 (95% CI 18.26-20.46) per 100,000 person-years. After 1998 the IR increased considerably, peaking at 34.34 (95% CI 32.84-35.85) per 100,000 person-years in 2002. Subsequently there was a slight decrease. The highest IR was observed in the non-specific category "Respiratory disorders in diseases classified elsewhere". By ILD subcategory, the greatest average increase during the study period was observed in "Respiratory disorders in diseases classified elsewhere".


CONCLUSIONS
The incidence rate of ILD in Denmark increased during the study period, most pronounced for ILDs associated with systemic diseases.
Kornum
Jette B
JB
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Aalborg, Denmark. j.kornum@rn.dk
Christensen
Steffen
S
Grijota
Miriam
M
Pedersen
Lars
L
Wogelius
Pia
P
Beiderbeck
Annette
A
Sørensen
Henrik Toft
HT
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D017563:Lung Diseases, Interstitial / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012042:Registries; D012189:Retrospective Studies; D055815:Young Adult