You can add one to your sample set.
AFAIK, worry is the main reason for poor sleep. And encountering posts like this at HN and in newspapers all the time may add to the problem.
For example, I had almost gotten back my sleep a couple of months back. And then, every newspaper (and HN) was full of this new research saying that lack of sleep alters genes. I didn't even have to read the articles, the headlines were enough: "Too little sleep is bad for you, it alters genes! My, oh my!". Thanks! Welcome back, sleep problems.
But on what grounds can they conclude that altered genes is bad for your health? The research sure says that things is happening in your body, and that some processes related to e.g. the immune system has been altered. But how bad is it really? Will you die earlier?
There are many things altering your genes. If I look at a picture of a cute kitten, I am pretty sure you can see that in my genes. Also, meditation dramatically alters you genes. (There are stories about monks who hardly need to sleep at all, because they get the rest they need through meditation.)
So, are there big problems with sleeping too little, are there really reasons to worry? I don't know. But like in in many other fields (e.g. nutrition), results of early studies have been stated as "facts", while later studies show that things are a bit more complicated. Antioxidants comes to mind.
There are research suggesting that too little sleep causes heart disease. (Note the word "suggests".) But, if there is a link, is the reason lack of sleep? Or does other factors add to it or cause it, e.g. eating more junk food, that you get more easily annoyed (increasing blood pressure), etc.?
I am not suggesting that you should sleep less, and I believe sleep is important. But I am unsure about how much you should worry if you sleep poorly.
In general, I believe more and more in eating balanced, exercising moderately (walking is good!), and most importantly, taking a break when my body tells me it's time to rest (listening to your body is underrated, and we learn from early childhood to suppress what it tells us). And, very important, stop reading health news. Because adding to almost any problem, is how media (and others) report findings to sell more of their products. They skew reality, and you probably end up worrying more than you should.