Characteristics of occupational cleaners in 13283 persons from Northern European population samples.

* p-values from Pearson´s chi-squared test.
† Any of the following: Born during winter months (December, January, February), maternal age >35 years, severe respiratory infection before the age of 5 years and/or maternal smoking.
‡ Asthma symptoms: Yes to three or more out of 6 questions on asthma-like symptoms.
§ Asthma after 16 years of age.
Characteristics of occupational cleaners in 13283 persons from Northern European population samples.