A study using data from a longitudinal cohort of middle-aged men and women examined the relationship between coffee consumption and risk for stroke over a 10-year follow-up. Previous research had reported a modest association with any coffee consumption; also, coffee was known to increase risk for cardiovascular disease. The study found that persons who reported drinking 1 to 2 cups per day did not have any increased risk for stroke compared to non-drinkers (RR = 1.0), those who drank 3 to 4 cups of coffee daily had a 50% increased risk for a stroke (RR = 1.50), and those who drank 5 or more cups of coffee had an 8% increased risk for stroke (RR = 1.08).

Which of the following criteria for causality could be called into question in this study?

- Temporal relationship
- Strength of the association
- Biological plausibility
- Dose-response effect