This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
A progressive increase or decrease of a disease over a long period of time, generally several years or decades is known as 
Select and explain. 
A. Secular trends, B. Cyclic trends, C. Seasonal trends, D. Periodic fluctuations
A: Secular trends
Answer: A: Secular trends 
Explanation: None