Studies have shown that someone who is a consistent snorer is more likely to end up as a sleep apnea sufferer in later life, so it follows that snoring and sleep apnea causes need to be looked at together.

What is a snore? It is the air turbulence that creates the noise, so familiar to snorer's suffering partners. This disturbed air flow is caused by the tissues behind the nose and mouth vibrating. This occurs when the airways are partially closed possibly due to lack of neck muscle tone or maybe some other physiological aspect likes a jaw line with an "overbite".

What is sleep apnea? In the most common type, obstructive sleep apnea, the muscle in the upper airways relaxes with sleep, becoming more and narrower. If the air passage closes completely, the sufferer may stop breathing for 10 seconds or more. Then the brain will (should) kick in to ask for more oxygen, to which the spluttering choking sufferer will oblige, grab a breath and go back to sleep, quite often none the wiser.

Overweight people tend to be snorers. Snorers tend to be generally less healthy with a higher chance of having high blood pressure, strokes and heart attacks.
Now the question is, do people snore and suffer from sleep apnea because they lead an "unhealthy lifestyle" with associated health risks, or is it the breathing disorder that is responsible for a higher than expected link to heart and blood pressure issues.
Research is revealing that snoring and obstructive sleep apnea are related to heart attacks, high blood pressure and strokes, independent of the association with smoking, alcohol intake, and weight.

It is small comfort to those healthy, jogging size eights out there who are afflicted, but around 40 percent of people with sleep apnea are NOT obese.

Snoring and sleep apnea causes
However weight is a significant factor in the cause of snoring but also age can play a part. As we age the muscles in the throat like the other muscles become less efficient.
Breathing in your own or other people's smoke can lead to a build up of congestion in the nasal passages making it more likely to breathe through your mouth resulting in more snoring.
Alcohol and drugs can also play their part. Alcohol is a sedative and it significantly relaxes the muscles in the throat, narrowing the passageways causing more snoring. Even after moderate alcohol intake, studies in Australia have shown that normally "harmless" snorers experienced bouts of sleep apnea in the first 2 hours of sleep.
The researchers measured the amount of oxygen absorbed by the blood in snorers who had been drinking and found a decrease of 27% absorption which is that much less oxygen reaching vital organs and tissues.
People who are already snorers and moderate to heavy drinkers are more likely to develop the more dangerous form of snoring, sleep apnea. 
Sleeping pills can have a similarly detrimental affect on breathing related sleep problems as the benzodiazepines drugs such as valium, again relaxes the throat muscles meaning more snoring.

Sleeping on your back can lead to snoring as the tongue falls back obstructing the throat.
Allergies such as hay fever and a reaction to house mites can cause that blocked up feeling in the nasal cavities.
Food type can also play their part as some people react with excessive mucus production in the nose and throat after a bout of having dairy consumption.

Snoring and sleep apnea cures don't really exist, but the symptoms can be greatly reduced with lifestyle changes and in the case of sleep apnea by using a continuous positive airway pressure (CPAP) machine.

There is also a device known as the mandibular repositioning splint which can be used for snoring or mild sleep apnea. This MRS or mandibular advancement device (MAD) is like a gum shield that goes over the teeth holding the lower jaw forward therefore maintaining the airspace opening at the back of the throat. See your dentist.

External nasal dilating strips can also be tried. These, like it says on the box are sticking strips that go across the nose and help dilate the nostrils but as snorers are mouth breathers these may not be very affective.

In conclusion
There are some connections between snoring and sleep apnea and both are very common, becoming more so which means snoring and sleep apnea causes are similar.
Persistent snoring can put an unbearable strain on relationships, can lead to medical problems and snorers are much more likely to develop sleep apnea.
90 percent of sleep apnea sufferers spend their days excessively tired, which can lead to all sorts of problems, apart from accidents, intellectual impairment, mood disturbances and reduced quality of life to name a few.

Medical professionals are taking sleeping disorders more seriously these days and it's important to seek their advice on long term management of the problem.