“Death by broken heart” can happen in that such a sudden and severe depression can reduce the immune system so that illness is more likely, and more likely to be severe. In addition, those who are grieving often neglect theiur own physical health and are less likely to see a doctor for problems.
There are statistically valid correlations between grief and sudden death. As this site puts it:
“The severe shock and sorrow can be enough for someone to want to follow their companion into death, to make them disillusioned with the medical profession so as not to seek care when needed, to manifest the same symptoms as experienced by the deceased, or perhaps be prone to accidents since they lose focus of the everyday world.”
However, as the article also makes clear, while the stress of loss can impact the health of the survivors, there are things one can do to help one progress through grieving. Taking care of oneself is vital, as is finding some way to express one’s feelings and figuring out what a new “normal” life will be without the deceased.
Find someone who will listen to you, figure out a way to memorialize the person you have lost, and take care of both your physical and social needs. It will get better, but since everyone grieves on a different schedule no one can tell you when that will be.
As one friend of mine said after having lost his wife of many years to a brain tumor in his seventies, and then his fiance to a car crash in his (and her) eighties, and then his second wife in his nineties to heart disease, “The only way to survive is to survive – go find things to do so being alive matters.” He is now in his nineties and serves as the trainer in the gym at the “senior living facility” where he and now my parents live.