Hi Shelagh,
 
Because pocket sprung mattresses usually have several layers of upholstery together with the metal pocket sprung unit, this tends to make them heavier than foam products. Having said that some memory foam or latex products themselves are on the heavy side and it may be best to look at elasticated bed linen to prevent you having to raise the mattress in order to make the bed. Please note that lighter weight mattresses tend not to be of any significant quality. I trust that this helps.
 
Kind regards,