| Course | HLTH 8035 Epidemiology: Decoding the Science of Public Health |
|---|---|
| Week | Week 8 |
| Paper type | Discussion post |
| Length | About 560 words, 4 pages |
| Format | Discussion post, APA 7 citations |
| School | Walden University |
| Program | PhD in Public Health |
| Updated | October 2026 |
Free sample paper for HLTH 8035 Week 8
Week 8 Discussion: Causal Language in Observational Studies
"Protects" Is the Word in Dispute: A Coffee and Parkinson's Cohort, a Long Prodromal Phase That Could Lower Intake Before Diagnosis, and the Verb the Design Can Support
The composite abstract concludes that "daily coffee consumption protects against Parkinson's disease." I want to set aside the finding for a moment and look at that verb. "Protects" claims that coffee prevents the disease, a causal statement. The question for this week is whether the study earned it.
The design is a prospective cohort. Roughly 60,000 adults reported their usual coffee intake once, at enrollment, and new Parkinson's diagnoses were identified over the following fourteen years through medical records. Daily drinkers had about 30% fewer diagnoses than non-drinkers after adjustment for age and sex. I should credit what this design does well. Because coffee was recorded before any diagnosis, it gets temporality more right than a survey asking people with and without Parkinson's what they drink now. The finding is also consistent with the wider literature: a meta-analysis of observational studies found lower Parkinson's risk among coffee drinkers, as it did among smokers (Hernán et al., 2002).
The case against the verb rests on the disease's long run-up. Parkinson's begins years, possibly decades, before diagnosis. During that prodromal phase, people can experience loss of smell, constipation, sleep disturbances and changes in mood (Postuma & Berg, 2016). Some of these changes could plausibly reduce a person's appetite for coffee or their tolerance of it. If so, people already on the path to Parkinson's at enrollment would report drinking less coffee, and lower intake would be an early consequence of the disease rather than its absence being a cause. A cohort that measures intake once, at the start, cannot distinguish these. The arrow could run from early disease to low coffee as easily as from coffee to protection. One test is available in the study's own data: excluding diagnoses made in the first several years of follow-up. If the association holds when early cases are removed, reverse causation becomes less likely, though with a prodrome this long, even ten years may not be enough.
I would replace "protects against" with "was associated with fewer later diagnoses of." That wording reports what the cohort found without asserting a mechanism. The stronger verb would need more: an association that persists after excluding many years of early cases, repeated measures showing intake did not fall before diagnosis, a dose-response pattern, and a plausible biological pathway with supporting evidence. Reviews of Parkinson's epidemiology have described caffeine as among the more consistent protective associations and noted proposed mechanisms (Ascherio & Schwarzschild, 2016), which is a reason to study it further, not a license for the verb.
Question for the board: is there any single-measurement cohort design that could justify "protects"?
Reply to Felix
Felix, you defend the authors on the grounds that the association has been replicated many times. Replication strengthens confidence that the association is real; it does not tell us its direction if every study measured intake once in adults who may already have prodromal disease. Consistent studies can share the same weakness.
Reply to Amara
Amara, you raise confounding by smoking, since smokers drink more coffee and smoking is also associated with lower Parkinson's risk. That is a fair concern, and the abstract adjusted only for age and sex. A stratified analysis among never-smokers would help separate the two.
References
Ascherio, A., & Schwarzschild, M. A. (2016). The epidemiology of Parkinson's disease: Risk factors and prevention. The Lancet Neurology, 15(12), 1257-1272. https://doi.org/10.1016/S1474-4422(16)30230-7
Hernán, M. A., Takkouche, B., Caamaño-Isorna, F., & Gestal-Otero, J. J. (2002). A meta-analysis of coffee drinking, cigarette smoking, and the risk of Parkinson's disease. Annals of Neurology, 52(3), 276-284. https://doi.org/10.1002/ana.10277
Postuma, R. B., & Berg, D. (2016). Advances in markers of prodromal Parkinson disease. Nature Reviews Neurology, 12(11), 622-634. https://doi.org/10.1038/nrneurol.2016.152
What the HLTH 8035 Week 8 instructions ask for
The eighth week asks students to examine the causal language in an observational study's abstract and judge whether the design supports it. A strong post isolates the verb or phrase in dispute, identifies the design and credits what it does well. It then names the specific alternative explanation the design cannot rule out, such as reverse causation, confounding or bias, and explains how it would operate in the case. Proposing a test the study could run, replacement wording and the evidence a stronger claim would require makes the critique constructive. A question for classmates closes the post. Replies should engage classmates' defenses or alternatives. Sources follow APA style. Posts should stay with one study rather than surveying a whole literature.
Inside the HLTH 8035 Week 8 example
The sample paraphrases the composite abstract and isolates "protects." It describes the cohort design and credits its temporal order, citing a meta-analysis of coffee, smoking and Parkinson's risk. The third paragraph explains that prodromal symptoms, documented in a review of early markers, could reduce coffee intake before diagnosis, and that excluding early diagnoses would test this. The fourth proposes associational wording and lists the evidence a causal verb would need, citing a review of Parkinson's epidemiology. One reply explains why replication does not settle direction; the other agrees that smoking is a likely confounder and suggests a never-smoker analysis. The cohort is composite; the cited reviews are real.
HLTH 8035 Week 8 rubric: what earns full marks
Posts on causal language are graded on precision. Faculty reward posts that isolate the disputed wording, credit the design's strengths and name a specific alternative explanation with a mechanism tied to the case. A testable proposal, such as excluding early follow-up, shows practical understanding. Replacement wording and a list of the evidence needed for a stronger claim earn credit. Posts that object to any causal language in observational studies without explaining why it fails here lose marks, as do posts that ignore the design's strengths. Faculty read the replies for whether they move the argument forward. Accurate citations are expected. Precision about the single word in dispute keeps the post focused.
HLTH 8035 Week 8 help: mistakes that cost marks
Posts on causal language often fall short by objecting that observational studies can never show causation, which skips the specific problem in the study. Another common problem is naming reverse causation without explaining how it would happen in the case. Some students also fail to suggest better wording. To write a stronger post, quote the disputed verb. Describe the design and credit what it does well. Explain one alternative explanation step by step. Propose a test the authors could run. Offer replacement wording and say what would justify the stronger claim. Students who want a post on causal wording in a study they are reading can ask our team for a draft. Stay with one abstract and one verb.
Get a HLTH 8035 Week 8 example written to your instructions
Send the abstract your Week 8 thread is examining, or its citation, with the prompt and your rubric. The post isolates the causal verb, tests it against the design, names the rival explanation most likely to account for the finding, and proposes wording the evidence supports. First sample free; 24-48 hours to delivery.
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HLTH 8035 Week 8 questions, answered
Where can I find a free HLTH 8035 Week 8 sample paper?
A complete Week 8 discussion post disputing the word "protects" in a composite coffee and Parkinson's cohort, with two replies and three references, is reproduced in full lower on this page.
Why does the HLTH 8035 Week 8 post reject "protects"?
Because Parkinson's has a long prodromal phase that could lower coffee intake before diagnosis, and a single baseline measure cannot rule out that reversal.
What test does the post propose?
Excluding diagnoses made in the first several years of follow-up to see whether the association holds.
What wording does the post suggest instead?
That daily coffee drinking "was associated with fewer later diagnoses of" Parkinson's disease.
Does replication answer the objection?
No; replication shows the association is consistent, but studies sharing the same single baseline measure share the same weakness about direction.