Apparent changes in incidence or mortality can occur over time (apparent trend) without real changes in actual rates. It is very important to consider these influences when analyzing trends.

(1) In 19th C. Europe TB was common and “consumption” a trendy, though tragic cause of death. In the operas La Boheme and La Traviata, both heroines die from TB, while the Romantic poet Shelley also succumbed. In the Oslo Art Gallery, a 19th C. painting “The Sick Child” depicts a young girl clearly dying from TB.