Sleep: the Silent Killer

• Read the rest of the newspaper article.  Based on the article, what do you think the study is saying?

The main message seems to be that sleeping more than 10 hours a night could be a sign that something is wrong.  This is suggested by the 3rd paragraph ("Researchers said underlying diseases...") and the 5th paragraph, quoting the lead researcher ("... it shows that excessive sleep ..."); the 7th paragraph is similar.

• To what extent does either headline fairly represent the rest of the newspaper article?

The print headline ("TOO MUCH SLEEP IS DEADLY") suggests that the sleep itself is harmful, whereas that does not seem to be the main focus of the rest of the article; the online headline is more explicit in this ("... more than ten hours a night increases stroke risk") and again differs greatly from the rest of the article.

• What does the word "associated" mean here?

"Associated" means that there is a statistical relationship between the two features.  In this case, the study suggests that mortality risk (chances of dying within 5 years, say) is lowest for people who sleep 7 to 8 hours per night and is higher for people outside this range, so the mortality risk is associated to the amount of sleep.

This does not, though, say that one causes the other, and the rest of the study (and some of the newpaper article) says this explicitly: the long amount of sleep could be indicative of some underlying health problem.

• How does this conclusion compare to the newspaper headline?

The newspaper headline (either version) suggests that too much sleep causes an increased mortality risk.  There is nothing in the study's conclusion which supports this claim.

• How does this conclusion compare to the rest of the newspaper story?  (You could analyse every paragraph if you have time to.)

Paragraph by paragraph:

1. ("While...") This paragraph hints that this is causative: the language "loves a lie in" suggests that this is a conscious choice to sleep in late.  The study seems more concerned with the average amount of sleep participants are getting rather than an occasional lie in.  One would have to lie in a huge amount to average over 10 hours of sleep per night!  With over 3 million people in the study, it is likely that the majority of those sleeping over 10 hours per night on average were not doing so by choice.
2. ("A major study...") This explicitly says that long periods of sleep cause an increased mortality risk, which is not what the study says.
3. ("Researchers said...") They did say this, though they weren't as dramatic as "in a bid to save their lives".
4. ("The study...") This was not mentioned in the conclusion, but is in the rest of the study.
5. ("Lead researcher...") This matches the study's conclusion, as long as we understand "is a marker" to mean something like "indicates" or "may indicate"; it is certainly associated with "elevated cardiovascular risk", so whether it means there is an increased risk or just that there may be an increased risk is somewhat nuanced.
6. ("Our findings...") This is not mentioned in the study's conclusion, but is a more nuanced version of paragraph 3.
7. ("If excessive...") This is a continuation of the previous paragraph.
8. ("The researchers...") The phrase "got too much sleep" is making a value judgement, whereas the study's conclusion does not.  Other than that, this matches the report's conclusion.
9. ("One, over 11 years,...") This is a detail from the study which we cannot judge from the study's conclusion alone.  It's somewhat imprecisely worded, though, as everyone will die eventually.  Also, since that study has finished, the language of probability is not quite correct.  It would be better to say something like "In one study considered by the researches, the proportion of people who reported sleeping for more than nine hours on average who died during the 11 years of the study was 25% greater than for the rest of the participants."  But that's a bit of a mouthful.
   Also, what does 25% greater mean?  If only 1% of the participants died during the 11 years, so 4 out of every 400 people, then this would mean that 5 out of every 400 long sleepers died during the 11 years, and that would not necessarily be a dramatic effect.
10. ("The review...") The conclusion said "Longer duration of sleep may be more associated with adverse outcomes compared with shorter sleep durations," so it suggests that there may have been adverse outcomes with shorter sleep durations too.  But we would have to read more of the study to see whether this is what was actually meant.
11. ("Dr Kwok...") This explains the research purpose, but does not give any results.
12. ("We further...") As with the previous paragraph.
13. ("There are cultural...") A probably uncontrovesial statement about sleep.
14. ("These include...") A description of modern life, expanding on the previous paragraph; again, this doesn't directly relate to the results of the study.
15. ("Some have...") This suggests that a longer duration of sleep causes problems, which is not what the study's conclusion says.  It may be the case, as these people have previously suggested, that there is a causal link, but this paragraph ties back to the headline which says that this link is causal.
16. ("Adults who...") This does seem to fit the wording of the study's conclusion, but contradicts paragraph 10 of the newspaper article.  (And what does "at risk of dying" mean?)
17. ("But until now...") This is not mentioned in the study's conclusion; it may or may not be the case.
18. ("The review...") This is a correct statement: it was published here on 3rd August 2018.

The overall impression is some mixture of the conclusion of the study and a suggestion that "excessive sleep" causes an increased mortality risks.

Clinical implications

• What does this suggest the authors of the scientific paper believe?  Does this fit better with the newspaper headline, with the report conclusion or neither?

It suggests that the authors believe that there might be a causal link between sleep quality and duration and cardiovascular health.  If there is, then advising people regarding their sleep might be beneficial.  It fits slightly better with the report conclusion, because it is not claiming that there definitely is a causal relationship.

• If the data only shows that there is an association between a longer duration of sleep and cardiovascular disease, but not that a longer duration of sleep causes cardiovascular disease, is advising people who sleep more than 7 to 8 hours to sleep less a good thing, a bad thing or neither?

This question itself - which is suggested by the newspaper article wording - somewhat misses the point.  The researchers did not suggest this, either in their conclusion or in their comment on clinical implications, but instead suggested that doctors should attempt to find reasons why a particular patient is sleeping for longer durations, and then if possible address those.  It seems unlikely that this would be a bad thing, especially if something such as obstructive sleep apnea is discovered.