A study confirming fewer people die in late summer and early fall suggests it's not all about the lack of extreme heat or cold, but perhaps also due to a combination of sunshine and time off.

Research published in the Canadian Medical Association Journal on Monday by Greek and American researchers shows that mortality rates are lowest in August in North America and Sweden, in September in Mediterranean countries and in March in Australia.

The authors suggest the physiological effect of increased vitamin D synthesis due to exposure to the sun, combined with the stress-relieving benefits of time off, may contribute to these lower mortality figures.

The study says increased vitamin D "may have beneficial effects for cardiovascular disease, renal failure, certain malignant diseases, autoimmune disorders and infections, including influenza," write Dr. Matthew Falagas of the Alfa Institute of Biomedical Sciences in Greece and his co-authors.

In general cold weather is associated with cardiovascular problems and respiratory infections. Hot weather carries the same risks, plus greater likelihood of death from gastrointestinal infections.

The researchers undertook the study in hopes that public health services might be directed to where the need is the greatest.