The latest study, presented at European Sleep Research Society's conference in Glasgow last month, suggests that some sufferers live longer than those who do not have the condition.
The new finding also indicates that doctors may be causing more harm to some patients than good by treating them for the disorder.
The study followed 611 patients aged 65 and over for more than four years.
According to the researchers, patients with moderate sleep apnoea were less likely to die over the course of the study than those who did not have the condition.
By the end of the four years, three times as many people without sleep apnoea died as had the condition.
Mortality rates among patients with light and severe sleep apnoea were the same as the general population, the study showed.
Peretz Lavie, who carried out the research at the Lloyd Rigler Sleep Apnoea Research Laboratory in Haifa, Israel, called the findings "astonishing".
"We know that sleep apnoea does reduce life expectancy for people under the age of 50, so to find that it could actually prolong life for elderly patients was quite a shock," the Telegraph quoted him as saying.
He now wants to identify the exact mechanism behind the syndrome, and discover whether there is a way to determine which patients are experiencing the benefits of sleep apnoea.
He said that the findings should change the way that doctors treat some patients with sleep apnoea.
He said: "At the moment we are treating people indiscriminately, but this study suggests that if elderly patients are not suffering any of the symptoms of sleep apnoea, then they should probably not be treated at all."