That may be, but you are still here typing. Deaths from nearly every cause of death (heart attack, stroke, cancer, etc) are higher in winter. There are no causes of death which decrease in winter except lightning, heat stroke and similar rarities.
I don't remember the article mentioning anything about kidney stones being a mortal illness. I would suppose death from kidney stones is pretty unusual. If you've ever had one you'll remember occasions when you wished you were dead, however.