The strongest effect was observed among working men. It is entirely possible that working men who have time to nap have less stressful jobs -- and that it's the lack of stress, not the lack of naps, that reduces their risk. In other words: Does napping reduce stress, or is it simply an indicator of someone who has a less stressful life, e.g., the kind of job in which they can take a snooze?
The study might have moved us toward an answer by rating participants' lives or jobs by their stress level, and using that as a control variable when examining the role of naps. It didn't go there. Therefore, we can't, either.
I spoke today with Dr. Dimitrios Trichopoulos of the Harvard School of Public Health, one of the study's authors. "It would be absolutely premature" to infer causality in the relationship between naps and lower risk of dying from a heart attack, he said. "Causality is a possible interpretation. But we are in no way there. I would like to see another three or four studies before I expressed some confidence in causality."
These reports recall last week's misreporting of the latest figures on autism from the Centers for Disease Control and Prevention in which a 14-state study has been widely and wrongly reported to be nationally representative, and widely and wrongly reported to have produced a sharply higher estimate of autism prevalence than any previous study.
One common point in all these studies is that they appear to have been well-constructed and based on good-quality data. That elevates them above all the manufactured junk data that clamors at our doors and all too often insinuates itself into our news reports. But still the reporting on these studies is not what it could have been.
One take-away is that news organizations -- including this one -- need to sharpen their efforts to report scientific studies accurately. Another is that, as a news consumer, when you see a report on a study that's of particular interest, you might take advantage of the beauty of the Internet -- and click through to the study itself.