Death comes, say the medical textbooks, when certain biological thresholds are exceeded and critical organs cease to function. The timing of death, then, is supposedly reduced to little more than the resolution of a complex biophysical equation _ as though the body were solely a piece of crafted machinery. But may the dying human have a conscious hand in modifying this equation: in changing the time when the breath of life ceases?

Admittedly, this has a suicidal ring to it. So let us reword the question. Can a terminally ill person consciously delay his or her death beyond a particular date — to cling to life, no matter how tenuously, until, say, a grandchild’s impending college graduation? Or to observe a special day, such as one’s birthday or wedding anniversary, or a revered religious or secular occasion?

Consider Thomas Jefferson, author of the Declaration of Independence. He died on the afternoon of July 4, 1826: 50 years to the day after his historic Declaration had appeared.

Moreover, his co-signer John Adams died that very afternoon. And, five years later, on July 4, 1831, James Monroe, also died.

Thus, three of the first five U.S. presidents died on the Fourth of July: a profoundly meaningful day to each of them.

A bookmaker, more interested in probability than sentimentality, would tell you that the likelihood of three such men dying on a particular date is extremely remote. None of the other American presidents have died on July 4 (although Calvin Coolidge was born on this date).

Biostatisticians have thus wondered whether some terminally ill people somehow extend their lives so that they can reach a day that is especially meaningful to them.

A number of studies have been conducted to determine whether any temporal relationship exists between an individual’s month of birth and month of death. One statistician, analyzing 261,226 deaths among older residents of England and Wales, concluded that death was more frequent in the months following one’s birthday than in the months preceding it. Interestingly, this temporal relationship _ purporting to show that the timing of death is both biologically and psychologically determined _ was more evident in the married than the unmarried.

A study of deaths in the United States confirmed this curious relationship between birth month and death month, but declared that such a statistical association prevailed only among dying adults older than 20.

A 1969 study of “famous” Americans (“fame” being determined by inclusion in Who’s Who and American-history texts) found that death rates appreciably decreased in the month immediately before the birth month, and significantly increased in the following month _ even though many of these deaths, due to such factors as assassination, were clearly beyond the person’s control.

A parallel analysis of “non-famous” Americans showed the same temporal relationship, though not so strikingly. (No analysis of “infamous” Americans has yet been undertaken.)

A Canadian study of death certificates replicated these findings. And a recent study of Rhode Island death certificates similarly confirmed a limited reprieve from death, a “death dip,” in relation to birth date.

Meanwhile, a study of death certificates of patients of some of the Massachusetts state hospitals for chronic disease (representing indigent people, largely without family) showed no relationship between date of birth and date of death.

Sociologists in New York State demonstrated a consistent dip in adult death rates _ a brief postponement of death _ immediately before presidential elections. A death dip also held true for the Jewish population before Yom Kippur, the annual Day of Atonement. (Sigmund Freud, who was Jewish, died on that date.)

Prompted by the studies demonstrating a postponement of death among Jews around the Jewish High Holy Days, West Virginia scientists conducted a parallel study of Appalachian death certificates, to determine whether any relationship existed between time of death among Christians and the Christian holidays of Christmas and Easter. They showed a peak in death in the two weeks after Christmas (particularly in small towns), although no such relationship with Easter.

What do all of these studies mean? Perhaps little beyond a few random coincidences. After all, many people die on the Fourth of July unaware of the date’s historic significance. But, alternatively, these studies may suggest that we have some slight leeway in the timing of our death. And if our terminal interlude approaches an important day _ our birthday, perhaps _ we might exert ourselves to survive through that auspicious day, especially if we consider ourselves important enough to celebrate the date.

Ecclesiastes informs us that “To everything there is a season, and a time to every purpose under the heaven: a time to be born and a time to die.” Yet the author of this text makes no mention of the determinants, and even the societal nuances, that may affect our time of death.

(Stanley M. Aronson, M.D., a weekly contributor, is dean of medicine emeritus at Brown University. This column is adapted from one in the current issue of Medicine & Health/Rhode Island, the monthly publication of the Rhode Island Medical Society.)