Directions: Study the graph “Parkinson’s risk is lower in patients with a cut vagus nerve” in the Science News article “Parkinson’s pathways” and answer the following questions.
Read the figure: Parkinson’s risk is lower in patients with a cut vagus nerve
Radical protection Because the vagus nerve is a route to the brain, scientists wondered if a severed vagus nerve helped protect against Parkinson’s. In one study, patients who had undergone one type of vagotomy had lower disease incidence starting five years later than people who did not have the surgery. Source: B. Liu et al/Neurology 2017
1. What variable is plotted on the x-axis of the graph? Make sure to include the unit of measurement for the variable.
Possible student response: The time in years since surgery to cut the vagus nerve.
2. What variable is plotted on the y-axis of the graph? Make sure to include the unit of measurement for the variable.
Possible student response: The cumulative incidence of Parkinson’s disease, as a percentage of each population.
3. What do the lines represent?
Possible student response: The dotted red line represents the population in the study that did not undergo vagus nerve surgery. The solid purple line represents the population in the study that underwent the vagus nerve surgery.
Interpret the graph:
4. According to the graph, what benefit is associated with the cut vagus nerve?
Possible student response: The population with the cut vagus nerve had a lower risk of developing Parkinson’s disease. At just shy of 30 years after surgery, the risk was a little less than 50 percent lower for those who had had surgery compared with people who had not had the surgery.
5. How long does it take for the cut vagus nerve to make an apparent difference in the cumulative Parkinson’s incidence?
Possible student response: The curve for people with a cut vagus nerve starts to diverge from the curve for people with an intact vagus nerve roughly seven years after surgery.
Connect the graph to the article:
6. What relationships might be further investigated based on the data given in the graph?
Possible student response: The data suggest an interesting link between a cut vagus nerve and Parkinson’s risk. It would make sense to further investigate this potential connection to see how the two may be connected. However, other factors probably also contribute to the development of Parkinson’s disease because the risk was not eliminated.
7. How does this figure support the general ideas in “Parkinson’s pathways?”
Possible student response: The graph shows an example that connections between the gastrointestinal tract and the brain could be involved in the development of Parkinson’s disease.
Analyze beyond the article:
8. What other observational study could you run in an attempt to understand Parkinson’s risk in relation to the gut?
Possible student response: I would like to compare how surgery or removal of different parts of the gastrointestinal tract, such as the appendix, affects Parkinson’s risk over time.