Two studies that have found some evidence that the timing of death responds to incentives created by changes in estate taxes:
1. From the USA: Kopczuk and Slemrod (2003), https://pdfs.semanticscholar.org/afd2/7f878ba71c9ec28258407a1e9b34150cd9d0.pdf
2. From Sweden: Eliason and Ohlsson (2013), http://www.diva-portal.org/smash/get/diva2%3A457378/FULLTEXT01.pdf.
These are far from definitive, but are definitely suggestive.
Here is another link: https://www.statnews.com/2016/09/23/end-of-life-dying-willpower/ that is more (anecdotal) evidence. Biologically, there is nothing magical about consciously pushing your body to stay alive for a little while longer if the situation is not acute, but chronic. Same with consciously letting go. Release of adrenaline or other hormones triggered by intense emotions happens all the time, and I don't see why end-of-life would be an exception.
Maybe we should differentiate holding off losing consciousness from holding off dying? Because I know that I can definitely hold off on falling asleep and maybe holding onto consciousness is the same?
My grandfather had a story that his dad waited him to return from school before he died from sudden stroke.
Also, I read somewhere that people who have carbon monoxide poisoning have to put effort to stay awake, because falling asleep is increasing chances of death. I think it is related to the intensity of breathing, which could be partly controlled.
The Birthday: Lifeline or Deadline? DAVID P. PHILLIPS, PHD, CAMILLA A. VAN VOORHEES, MD, TODD E. RUTH
This study of deaths from natural causes examined adult mortality around the birthday for two samples, totalling 2,745.149 people. Women are more likely to die in the week following their birthdays than in any other week of the year. In addition, the frequency of female deaths dips below normal just before the birthday. The results do not seem to be due to seasonal fluctuations, misreporting on the death certificate, deferment of life-threatening surgery, or behavioral changes associated with the birthday. At present, the best available explanation of these findings is that females are able to prolong life briefly until they have reached a positive symbolically meaningful occasion. Thus, the birthday seems to function as a 'lifeline' for some females. In contrast, male mortality peaks shortly before the birthday, suggesting that the birthday functions as a 'deadline' for males.
See also:
December 22/29, 2004 Holidays, Birthdays, and Postponement of Cancer Death Donn C. Young, PhD; Erinn M. Hade, MS Article Information JAMA. 2004;292(24):3012-3016. doi:10.1001/jama.292.24.3012
Hmm, color me suspicious. I'm not saying it's not true, just that this sounds like the kind of thing that wouldn't replicate.
Given that euthanasia is illegal and at the same time it's possible to make people die faster by giving them more morphine. That's going to be hard to factor out of the data.
content note: death, old age, sickness
I've heard numerous anecdotal accounts of sick or old people who are on death's door "holding on" in a way suggestive that they were exerting some effort to do, until they had reached closure on some thing (a relative coming to visit, a manuscript published, somebody's birthday).
I could imagine this being a totally real thing that dying people can do for some limited time.
I can also imagine it just being cherry picked stories that were more a matter of luck.
It seems likely that there's at least situations where, say, eating is difficult/painful, and people continue exerting effort to do that so long as they have something that feels worth it to keep doing so, and then stop putting in the effort after hitting some milestone they cared about.
Some of the anecdotes I've heard implied something more immediate going on (where someone seemed to be holding on and literally a few minutes or seconds afterwards, died).
(Possible straightforward mechanism could just be that breathing becomes painful and difficult, and people only keep doing it when they have a concrete goal)