Sleeping too much or too little linked to chronic diseases

A couple of paragraphs to whet your appetite. Is your doctor warning you not to be either a short or long sleeper? If left to my own devices my fatigue will make me a long sleeper.
http://www.medicalnewstoday.com/articles/267075.php
The data showed 31% of the participants were "short sleepers" who slept an average of 6 hours or less in a 24-hour period, over 65% were "optimal sleepers" who slept 6 to 9 hours on average, and 4% were "long sleepers" who slept an average of 10 hours or more.
When they analyzed the relationships between sleep and health, the team found that compared with optimal sleepers, short sleepers tended to suffer more from coronary heart disease, stroke and diabetes, as well as obesity and frequent mental distress.
They found the same was true of long sleepers, except in their case, links with coronary heart disease, stroke and diabetes were even stronger.