The NHS has been urged to place greater emphasis on supporting vulnerable groups during periods of moderately cold rather than freezing temperatures after a study suggested this is when services come under greatest strain.

Public Health England has partially adapted this year’s Cold Weather Plan in line with the preliminary findings of a Department of Health-commissioned report produced by the London School of Hygiene and Tropical Medicine.

This year’s plan, released late last month, urged changes to year-round planning and winter preparedness plans to reflect the study’s findings that “indicate that the greatest total health burden occurs at relatively moderate cold temperatures”.

It added: “This means that action to prevent excess winter morbidity and mortality should not be restricted to the very cold days, but should be carried out throughout the winter period.”

Increased risk kicks in at temperatures of about 5-8°c, depending on region. In previous years the plan has advised that certain actions should only kick in when the temperature drops below 2°c.

Nick Mays, of the school’s policy innovation research unit, told HSJ on Friday: “There’s also some evidence that cold but not freezing temperatures increase the infection risk of things like the flu virus.

“My take on all of this is that winter is the issue, not the extremes of winter. The key thing I think is the way that community services prepare for winter and also to do a patient medication check in the autumn.

“It doesn’t have to be anywhere near freezing for the veins in the peripheral parts of the body to start to constrict and that means therefore that the volume of blood that can pass through veins shrinks and the blood clotting proteins - which are big molecules - are more concentrated. That increases the risk of heart attacks and strokes.”

PHE said it had not made more specific recommendations because the study’s findings have not yet been verified.

The final report is expected to be published this month.