All standard factors affecting sleep were accounted for in the study. These included, age, sex, weight, marital status, blood pressure, diabetes, cholesterol levels, amount of exercise done, educational standard and whether work was shift work. Any history of depression or anxiety was also noted as these are known to affect the ability to have a good night’s sleep.

The study found that about one third of the population has at least one symptom of insomnia. It was also noted that previous small scale research had identified an association between insomnia and heart disease, high blood pressure and increased heart attack risk was also seen to be linked in some way.

The researchers acknowledge that the study had limitations. They carried out the survey in Norway, a country which has very light summers and very dark winters. It is known that long periods of darkness can affect some people’s well being and sleep patterns. And the disorder known as sleep apnea was not considered during the study. This condition disrupts sleep by causing shallow breathing or lapses in breathing regularity.

Dr. Gregg Fonarow, professor of cardiology at the University of California, Los Angeles and spokesman for the American Heart Association, acknowledges that earlier studies have taken place to investigate the link between disturbed sleep and increased risk of heart attacks. He says, "These prior studies have yielded mixed results, and it remains unknown if better sleep means a healthier heart".

He says that this large scale study indicates that if people cannot get to sleep, stay asleep or waken up unrestored then they will moderately increase their risk of heart attack within the next ten years. He went on, "Further research is needed to confirm these findings, explore the potential mechanisms involved, and determine if interventions that effectively treat insomnia can reduce the risk of acute myocardial infarction".

Dr. Edward A. Fisher, The Leon H. Charney Professor of Cardiovascular Medicine at NYU Langone Medical Center in New York City, says that one possible reason for the study’s findings is that the circadian rhythm in the body, which controls all metabolic processes, fluctuates appreciably when going between sleep-awake cycles. He says, "It is known that animals with disrupted circadian rhythms develop metabolic changes that, if they occurred in people, would increase heart disease risk". He goes on to say that the link is credible although the exact process is unknown. He agrees with the authors when they say if you have difficulty sleeping go and get professional advice. Fisher adds "Besides improving the general quality of life, it might even provide cardiovascular benefits".