Brain death occurs when there is a total and irreversible loss of all the brain's functions. Organ donation most commonly occurs when there is a brain death.

Causes of brain death can include:

• blood vessel injury, such as a stroke or aneurysm
• prolonged anoxia, such as might occur after a drowning or heart attack when a person is revived but the brain went to long without oxygen
• injury to the brain from fall or blow
• gunshot
• motor accident

Dr. Andreas Kramer and colleagues at the University of Calgary, Alberta, recently published a study investigating changes in the availability of donated organ tissue over the last decade. The rate of organ donation is in decline despite significant efforts to educate the public.

"In Canada and in the U.S., the most common scenario where a dying patient can become an organ donor is if they have progressed to this state called brain death, which is the irreversible cessation of all brain function," Kramer said. "It usually means there’s no blood flow to the brain either. That patient is very appropriate to become an organ donor."

The rate of neurologic death in brain trauma has dramatically reduced as indicated by the study. Kramer and his team looked at neurologic death over an 11-month interval, and they found the death reduction was greatest among traumatic injury.

Of the 2,788 cases studied, more than half were in the traumatic brain injury category, and the rate of brain death dropped from 6.1 percent to 2.8 percent during the study period. With fewer brain deaths, there are fewer viable organs for transplantation.

"Contemporary data indicate that donation after neurologic death accounts for about one-half of kidney transplants, more than three-quarters of liver transplants, over 90 percent of pancreas and lung transplants, and all heart and small bowel transplants," Kramer said.

Kramer offers an explanation as to the decline in organs and increased survival of those with neurologic brain damage. The decline in organ donation can in part be attributed the increasing improvement in emergency medical care and survival of those with brain injury, who in previous decades suffered death when a significant trauma to the brain occurred.

"When patients are injured and have a head injury, there's a whole number of steps in caring for those patients: getting the ambulance on scene, getting patients transferred and getting things they need to have done at a trauma center," he said. "Today, there’s faster transportation, trauma teams are better organized, and neurosurgeons tend to be more aggressive in caring for those patients ... I think it would be simplistic to attribute (the numbers) to just one thing."

Also contributing to the decline in organ donation is the reduction in substantial numbers of head injury within those states having mandatory motorcycle helmet laws. In a blog post for The New York Times, Jerry Garrett quotes an unidentified transplant surgeon: "Motorcycle fatalities are not only our No. 1 source of organs, they are also the highest-quality source of organs, because donors are usually young, healthy people with no other traumatic injuries to the body, except to the head."

Garrett was also discussing a California law that mandated helmets. After the law took effect in 1992, deaths from motorcycle head trauma dropped considerably as did the donation of transplantable organs from deceased motorcyclists. A study of transplant donation after a law passed in 1997 in Taiwan mandating motorcycle riders wear a safety helmet also found a drop in organ donation from head injury.

Motorcycles comprise about 2 percent of the registered vehicles in the United States but are involved in 10 percent of traffic deaths. When in an accident, motorcycle riders are 34 times more likely to die than automobile drivers, and the conclusions in a study of helmet laws across all 50 states was that helmet use saves lives.

But it is not just survival from traumatic brain injury or the reduction of risk of head injury that is impacting organ donation. Recent work by Dr. Mala Sachdeva and her collaborators of North Shore-LIJ Health System Transplant Center on Long Island, N.Y., found that obesity is a barrier to elective live donation of kidneys for transplantation.

The ever-increasing rate of obesity is and will have an impact on the availability of donor kidneys. Sachdeva's team of investigators found that among the 104 potential living kidney donors seen over a period between 2008 and 2011 that only 18 percent had a body mass index that fell in the normal range. They found that the majority of potential donors were in the overweight to obese category, and this put transplant specialists in a position to reject 25 percent of potential donations.

Sachdeva laments the impact obesity has on donation: "As the kidney transplant waiting list grows, there is a great need for living donors ... As a community we need to identify ways to overcome this barrier so that we can increase our donor pool and end the wait for transplant."

It is a bit ironic that the increase in survival for one group — by ratcheting down a carefree fast and furious lifestyle of motorcycle riders — we have negatively impacted the donation numbers for organ transplant.

But for yet another group, it is necessary to ratchet up a possibly slow, sluggish and not-so-fast-and-furious lifestyle. This would increase not only the individual with obesity's chance of survival, but also the opportunity to donate a life-saving organ.