Dot Earth Blog: A Small Island Takes a Big Step on Ocean Conservation

Photo A map of protected marine zones that are being established around the Caribbean island of Barbuda.Credit Waitt Institute

Marine life in the Caribbean has been badly hurt in recent decades by everything from an introduced pathogen that killed off reef-grooming sea urchins to more familiar insults like overfishing and impacts of tourism and coastal development.

Some small island states are now trying to restore once-rich ecosystems while sustaining their economies. A case in point is Barbuda, population 1,600 or so, where the governing council on Aug. 12 passed a suite of regulations restricting activities on a third of the island's waters. The regulations and reef "zoning," in essence, came about after months of discussions involving fishing communities, marine biologists and other interested parties, facilitated by the Waitt Institute, a nonprofit conservation organization.

Of course, it'll take time to see if the ambitious marine zoning plan works as intended. Local fishermen are seeking help finding new sources of income, according to the Antigua Observer.

But the process, which took nearly two years of study and meetings, provides a promising template not only for other island communities but also for any region where environmental restoration efforts have to mesh with local economic concerns.

The best way to avoid resistance is to involve affected communities from the start. The initiative brings to mind the Cheonggyecheon stream restoration project in the heart of Seoul that I wrote about in 2009. The mayor's team held hundreds of meetings with merchants and residents to work out issues and explain benefits.

Here's a piece describing Barbuda's "Blue Halo" initiative, written by Arthur Nibbs, the chairman of the Barbuda Council and minister of fisheries of Antigua and Barbuda, and Ayana Elizabeth Johnson, a marine biologist and the Waitt Institute executive director (and National Geographic blogger):

How to Use the Ocean Without Using it Up

By Minister Arthur Nibbs and Ayana Elizabeth Johnson, Ph.D.

Small islands face big ocean problems, but the solutions can be simple. Set some areas aside, protect key species, and prevent habitat damage. This will benefit the economy, help ensure food security, and allow the ocean to be used sustainably, profitably, and enjoyably, for this and future generations.

A year-and-a half ago, the Barbuda Council and the Waitt Institute forged a partnership to envision a sustainable ocean future for the island of Barbuda and launch the Barbuda Blue Halo Initiative. Put simply, we collaborated to design a plan to use the ocean without using it up.

This month, the Barbuda Council signed into law a sweeping set of new ocean management regulations that zone the coastal waters, strengthen fisheries management, and establish a network of marine sanctuaries. Barbuda may be a small island, but we hope the big commitment represented by these new policies will set an inspiring example for the region.

The new regulations create five marine sanctuaries, collectively protecting 33% (139 square kilometers) of the coastal area, and initiate a two-year hiatus on fishing in Codrington Lagoon to enable fish populations to rebuild and habitats to recover. Catching parrotfish and sea urchins has been completely prohibited, as those herbivores are critical to keeping algae levels on reefs low so coral can thrive. Barbuda is the first Caribbean island to put either of these important, strong measures in place.

Of course, if the community didn't support this, it wouldn't work. Therefore, to ensure the new policies reflect stakeholders' concerns and priorities, there were six rounds of community consultations. The final zoning map is the fourth iteration – the boundaries have changed dramatically since the Council's initial draft. The prohibition of using nets on the reefs was included at the request of local fishers concerned with reef damage. Though there will never be 100% agreement, this has been a consensus-seeking process and the Council aimed to balance current and future needs to use ocean resources.

Why were these measures necessary? First, Caribbean-wide, communities are seeing declines in the health of coastal ecosystems and fish populations. Barbuda is no exception. On average, Barbuda's reefs are 79% covered in algae, with less than 14% living coral. This is not good for fishing or tourism; fish need habitats and tourists want to see vibrant abundance.

Second, fishers now have to go further and into deeper water to make a good catch. This is expensive in fuel and it is dangerous. The regulations aim to rebuild coastal fisheries and ensure fishers have a livelihood that will last in perpetuity. Some people will say that these policies are meant to hurt fishers, but that couldn't be further from the truth. The sanctuaries were created to replenish the surrounding fishing areas.

Third, Barbuda is highly endangered by climate change and sea level rise. The coral reefs and mangroves buffer the island from the impacts of storms, so by protecting the reefs and mangroves, they will in turn protect the island. Healthier reefs will also be more resilient to impacts like warming sea temperature that can't be prevented locally.

Last, but certainly not least, dwindling coastal resources threaten local culture. The people of Barbuda have a strong connection to the sea – fish fries, camping on the beaches, kids growing up learning to fish with their parents and grandparents. In order to preserve this way of life, ocean ecosystems must be protected.

Over the next several years, the Barbuda Council and Waitt Institute will continue to work closely as these regulations are implemented. The Institute will help to set up a long-term scientific monitoring program, train local staff in marine ecology and field research techniques, design enforcement approaches, provide needed equipment, and work with the schools to develop an ocean education curriculum.

Unfortunately, Barbuda is not unique in facing these challenges – degraded coral reefs, depleted fisheries, and climate change impacts are nearly ubiquitous globally. So putting strong ocean policies in place is merely the first step, and we hope that more and more nations will take this step alongside Barbuda.

Here's a helpful presentation on the Blue Halo initiative given in July at the Scripps Institution of Oceanographyby Stephanie Roach, who worked with the Waitt Institute on the project over the past year:

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Well: Legal Marijuana for Parents, but Not Their Kids

Photo Credit Stuart Bradford

The Well Column

Tara Parker-Pope on living well.

When the antidrug educator Tim Ryan talks to students, he often asks them what they know about marijuana. "It's a plant," is a common response.

But more recently, the answer has changed. Now they reply, "It's legal in Colorado."

These are confusing times for middle and high school students, who for most of their young lives have been lectured about the perils of substance abuse, particularly marijuana. Now it seems that the adults in their lives have done an about-face.

Recreational marijuana is legal in Colorado and in Washington, and many other states have approved it for medical use. Lawmakers, the news media and even parents are debating the merits of full-scale legalization.

"They are growing up in a generation where marijuana used to be bad, and maybe now it's not bad," said Mr. Ryan, a senior prevention specialist with FCD Educational Services, an antidrug group that works with students in the classroom.

"Their parents are telling them not to do it, but they may be supporting legalization of it at the same time."

Antidrug advocates say efforts to legalize marijuana have created new challenges as they work to educate teenagers and their parents about the unique risks that alcohol, marijuana and other drugs pose to the developing teenage brain.

These educators say their goal is not to vilify marijuana or take a stand on legalization; instead, they say their role is to convince young people and their parents that the use of drugs is not just a moral or legal issue, but a significant health issue.

"The health risks are real," said Steve Pasierb, the chief executive of the Partnership for Drug-Free Kids. "Every passing year, science unearths more health risks about why any form of substance use is unhealthy for young people."

Already nearly half of teenagers — 44 percent — have tried marijuana at least once, according to data from the partnership. Regular use is less common. One in four teenagers report using marijuana in the past month, and 7 percent report frequent use — at least 20 times in the past month.

Even in the states where marijuana is legal, it remains, like alcohol, off-limits to anyone younger than 21. But the reality is that once a product becomes legal, it becomes much easier for underage users to obtain it.

This summer, the Partnership for Drug-Free Kids released its annual tracking study, in which young people were asked what stopped them from trying drugs. Getting into trouble with the law and disappointing their parents were cited as the two most common reason young people did not use marijuana. The concern now is that legalization will remove an important mental barrier that keeps adolescents from trying marijuana at a young age.

"Making it legal makes it much more accessible, more available," said Dr. Nora Volkow, the director of the National Institute on Drug Abuse. "This is the reality, so what we need to do is to prevent the damage or at least minimize it as much as possible."

Drug prevention experts say the "Just Say No" approach of the 1980s does not work. The goal of parents should not be to prevent their kids from ever trying marijuana.

Instead, the focus should be on practical reasons to delay use of any mind-altering substance, including alcohol, until they are older.

The reason is that young brains continue to develop until the early 20s, and young people who start using alcohol or marijuana in their teens are far more vulnerable to long-term substance-abuse problems.

The brain is still wiring itself during adolescence, and marijuana — or any drug use — during this period essentially trains the reward system to embrace a mind-altering chemical.

"We know that 90 percent of adults who are addicted began use in teenage years," Mr. Pasierb said. "They programmed the reward and drive center of their teenage brain that this is one of those things that rewards and drives me like food does, like sex does."

Studies in New Zealand and Canada have found that marijuana use in the teenage years can result in lost I.Q. points. Mr. Pasierb says the current generation of young people are high achievers and are interested in the scientific evidence about how substance use can affect intelligence.

"You have to focus on brain maturation," he said. "This generation of kids wants good brains; they want to get into better schools. Talk to a junior or senior about whether marijuana use shaves a couple points off their SATs, and they will listen to you."

Because early exposure to marijuana can change the trajectory of brain development, even a few years of delaying use in the teen years is better. Research shows that young adults who smoked pot regularly before the age of 16 performed significantly worse on cognitive function tests than those who started smoking in their later teenage years.

Drug educators say that one benefit of the legalization talk is that it may lead to more research on the health effects of marijuana on young people and more funding for antidrug campaigns.

The Partnership for Drug-Free Kids plans to continue its "Above the Influence" marketing campaign, which studies show has been an effective way of reaching teenagers about the risks of drug use. The campaign does not target a specific drug, but it teaches parents and teens about the health effects of early drug use and tries to empower teens to make good choices.

"Legalization is going to make the work we do even more relevant," Mr. Pasierb said. "It's part of the changing drug landscape."

A version of this article appears in print on 08/19/2014, on page D1 of the NewYork edition with the headline: In Drug Fight, Erratic Cues for Teenagers.

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Dot Earth Blog: Heading Down East for a Spell

I'm going to be in slow blogging mode through the coming week, on a long-overdue visit to Winter Harbor, Me., where my mother in law was born, resides and paints. It's mostly a sleepy backwater, but once a year things get very loud and fast.

To get a feel for the place, read a couple of my past reports for The Times from the region — on the annual lobster boat races and a boom in the 1990s in sea urchin harvests bound for Japan.

This video shows you just a touch of the quiet corners out along Schoodic Point, with the soundtrack an instrumental I wrote for my wife long ago. I hope you get a break from your hubbub this summer at some point, as well. Use the comment thread below for civil discussion of the merits of quiet times, taking a breath, just being.

Here's a bit more video in which the only music is the soft call of a cedar waxwing:

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Well: Rustle, Tingle, Relax: The Compelling World of A.S.M.R.

A few months ago, I was on a Manhattan-bound D train heading to work when a man with a chunky, noisy newspaper got on and sat next to me. As I watched him softly turn the pages of his paper, a chill spread like carbonated bubbles through the back of my head, instantly relaxing me and bringing me to the verge of sweet slumber.

It wasn't the first time I'd felt this sensation at the sound of rustling paper — I've experienced it as far back as I can remember. But it suddenly occurred to me that, as a lifelong insomniac, I might be able to put it to use by reproducing the experience digitally whenever sleep refused to come.

Under the sheets of my bed that night, I plugged in some earphones, opened the YouTube app on my phone and searched for "Sound of pages." What I discovered stunned me.

There were nearly 2.6 million videos depicting a phenomenon called autonomous sensory meridian response, or A.S.M.R., designed to evoke a tingling sensation that travels over the scalp or other parts of the body in response to auditory, olfactory or visual forms of stimulation.

The sound of rustling pages, it turns out, is just one of many A.S.M.R. triggers. The most popular stimuli include whispering; tapping or scratching; performing repetitive, mundane tasks like folding towels or sorting baseball cards; and role-playing, where the videographer, usually a breathy woman, softly talks into the camera and pretends to give a haircut, for example, or an eye examination. The videos span 30 minutes on average, but some last more than an hour.

For those not wired for A.S.M.R. — and even for those who, like me, apparently are — the videos and the cast of characters who produce them — sometimes called "ASMRtists" or "tingle-smiths" — can seem weird, creepy or just plain boring. (Try pitching the pleasures of watching a nerdy German guy slowly and silently assemble a computer for 30 minutes.)

Two of the most well-known ASMRtists, Maria of GentleWhispering (more than 250,700 subscribers) and Heather Feather (more than 146,500 subscribers), said that although they sometimes received lewd emails and requests, many of their followers reached out to them with notes of gratitude for the relief from anxiety, insomnia and melancholy that their videos provided.

Some say the mundane or monotonous quality of the videos lulls us into a much-needed state of serenity. Others find comfort in being the sole focus of the A.S.M.R. actor's tender affection and care. Or perhaps the assortment of sounds and scenarios taps into pleasing childhood memories. I grew up falling asleep hearing the sounds from my father's home office: A computer engineer, he was continually sorting through papers, tapping keys  and assembling and disassembling PCs and MACs.

Dr. Carl W. Bazil, a sleep disorders specialist at Columbia University, says A.S.M.R. videos may provide novel ways to switch off our brains.

"People who have insomnia are in a hyper state of arousal," he said. "Behavioral treatments — guided imagery, progressive relaxation, hypnosis and meditation — are meant to try to trick your unconscious into doing what you want it to do. A.S.M.R. videos seem to be a variation on finding ways to shut your brain down."

So far, it seems to work for me. Like many insomniacs, I have over the years tried natural remedies like valerian root or melatonin, vigorous exercise regimens and strong sleeping pills like Ambien and Lunesta. But sleep rarely came. Nothing has worked as well and consistently as watching a man in an A.S.M.R. video sort through papers and his collection of Titanic paraphernalia.

But locating the neurological underpinnings of this trippy sensation won't be easy. Many of the scientists I reached out to shied away from the subject, saying the area is pseudoscience with a lack of published studies.

Bryson Lochte, a post-baccalaureate fellow at the National Institute on Drug Abuse who looked into A.S.M.R. for his senior thesis as a neuroscience major at Dartmouth College last year, has submitted his paper for publication in a scientific journal. Mr. Lochte said, "We focused on those areas in the brain associated with motivation, emotion and arousal to probe the effect A.S.M.R. has on the 'reward system' — the neural structures that trigger a dopamine surge amid pleasing reinforcements, like food or sex.

He compared A.S.M.R. to another idiosyncratic but well-studied sensation called musical frisson, which provokes a thrilling ripple of chills or goose bumps (technically termed piloerection) over one's body in emotional response to music. Mathias Benedek, a research assistant at the University of Graz in Austria who co-authored two studies on emotion-provoked piloerection, says A.S.M.R. may be a softer, quieter version of the same phenomenon. "Frisson may simply be a stronger, full-blown response," he said. And like A.S.M.R., the melodies that ignite frisson in one person may not in another.

Robert J. Zatorre, a professor of neuroscience at the Montreal Neurological Institute and Hospital at McGill University who has also studied musical frisson, said that "the upshot of my paper is that pleasurable music elicits dopamine activity in the striatum, which is a key component of the reward system" in the brain. Writing in The New York Times last year, in an article titled "Why Music Makes Our Brain Sing," he notes, "What may be most interesting here is when this neurotransmitter is released: not only when the music rises to a peak emotional moment, but also several seconds before, during what we might call the anticipation phase."

Perhaps the everyday experiences that A.S.M.R. videos capture — whispering, crinkling, opening and closing of boxes — evoke similar anticipatory mechanisms, sparking memories of past pleasures that we anticipate and relive each time we watch and listen.

"The whole topic is still very much unknown," Mr. Lochte said. "I would be very interested to see what other traits correlate with A.S.M.R sensitivity, whether it is an inherited attribute and what sort of physiological effects the sensation has on the body. All of these questions will be easy to answer with quick follow-up studies. Our study, we hope, will help lay the groundwork."

A version of this article appears in print on 07/29/2014, on page D6 of the NewYork edition with the headline: A Tingly Feeling, Then Zzzzzz.

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Dot Earth Blog: New Approach to Being There: ‘Fan-bots’ Will Cheer Korean Baseball Team

Starting with childhood visits to dusk summer softball games in East Greenwich, R.I., and then a couple of memorable trips to Fenway Park, baseball always had a visceral feel for me that was never matched on a television screen.

Now television is looking visceral compared to the latest innovation — "fan-bots" set in the somewhat depopulated stadium of a Korean baseball team, the Hanwha Eagles. (Here's a BBC report and a darkly amusing CBS Sports commentary.) Through your smartphone you will be able to cheer on your favorite players, even customize your surrogate by adding your own features to its glowing "face."

Watch the promotional video above and ponder William Gibson's famous remark: "The future is already here – it's just not evenly distributed."

Let's hope this is just one future.

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Dot Earth Blog: Fresh Focus on Siberian Permafrost as Second Hole is Reported

Photo Scientists recently inspected a hole discovered in the Siberian tundra. It's a natural feature that will likely become a lake like the one at left.Credit Press service of the Governor YaNAO

Photo A hole in the Siberian permafrost probably formed when gas pressure built in a mix of water, ice and soil beneath, scientists say.Credit Press service of the Governor YaNAO

I had a Skype chat Wednesday about Siberian permafrost in the context of climate change with Marina Leibman, a top Russian permafrost expert who had just returned from examining the unusual crater spotted on the Yamal Peninsula in Siberia late last week.

We talked just before fresh reports circulated about reindeer herders finding another such hole in the region. I hope you'll watch our chat, which I regret I have not yet had time to transcribe (if you are in the mood, I'd be grateful for help; it's just 15 minutes long):

A Top Russian Permafrost Scientist on Siberian Holes and Climate Change

Photo Marina Leibman, one of Russia's leading permafrost researchers, during a recent visit to a spot where a large hole appeared in the Siberian tundra.Credit Press service of the Governor YaNAO

Leibman, the chief scientist at the Earth Cryosphere Institute of the Siberian Branch of the Russian Academy of Sciences, has studied permafrost since 1973 and has a remarkable publication record.

She describes how the first hole (and presumably the new one) appear to have formed as methane is released from a warming mix of ice, water and soil, building up pressure that explosively pushed out the top of the hole, heaving chunks of earth many yards in some directions. She said there were no signs of combustion, that the hole had to be at least a year old because there was fresh greenery from this summer season with no overlying layer of mud or the like.

Leibman stressed that there were no indications that such events were more than the normal process of lake formation in the area and predicted that the hole she inspected would end up being a lake in coming years.

She also stressed that she sees no signs of current or imminent warming producing a great destabilization of permafrost in the Arctic: "You can't say in 20 years it will be 2 degrees warmer so permafrost will be thawing. It will make it 2 degrees warmer, but not thawing – at least in the far north.

"In the south, where you have only patches of permafrost, the response may be a little bit more active," she said. "But what we see now is permafrost with minus 1 degree temperature [Celsius] now — after a climate warming of 1 and a half degrees — permafrost temperature is minus 0.1 degree, but not above zero."

I encourage you to listen to our conversation and learn more.

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Dot Earth Blog: Scientists Begin to Demystify Hole Found in Siberian Permafrost

After a flood of speculation — meteorite collision, methane explosion related to gas drilling, UFO — following the discovery of a gaping crater in the permafrost near big gas fields on the Yamal peninsula in Siberia, scientists are starting to offer more informed views.

Photo A view from the edge of a crater – about 100 feet across – that has opened in Siberian permafrost.Credit Marya Zulinova, press service of the Governor YaNAO

The Siberian Times, the source of initial aerial images and video, has posted the first article citing scientists at the scene. Here are some excerpts.

Photo Scientists are studying a hole discovered in Siberian permafrost.Credit Marya Zulinova, press service of the Governor YaNAO

The crater is smaller than initial reports:

Andrey Plekhanov, Senior Researcher at the State Scientific Centre of Arctic Research, said: "The crater has more of an oval than a circular shape, it makes it harder to calculate the exact diameter. As of now our estimates is about thirty metres."

Here's more from Plekharov, on a possible connection to the warming climate:

"Could it be linked to the global warming? We have to continue our research to answer this question. Two previous summers – years 2012 and 2013 were relatively hot for Yamal, perhaps this has somehow influenced the formation of the crater. But we have to do our tests and research first and then say it more definitively."

He also rebutted speculation that the black marks around the perimeter indicated a fiery explosion had taken place (one example):

"For now we can say for sure that under the influence of internal processes there was an ejection in the permafrost. I want to stress that it was not an explosion, but an ejection, so there was no heat released as it happened."

Earlier scientists were sure there was burning visible on the sides of the crater.

"I also want to recall a theory that our scientists worked on in the 1980s — it has been left and then forgotten for a number of years. The theory was that the number of Yamal lakes formed because of exactly such natural process happening in the permafrost.

Such kind of processes were taking place about 8,000 years ago. Perhaps they are repeating nowadays. If this theory is confirmed, we can say that we have witnessed a unique natural process that formed the unusual landscape of Yamal peninsula."

Photo A diagram from the British Society for Geomorphology explains the formation of a pingo, a hill formed around a buried lump of ice in regions with frozen ground, or permafrost.Credit British Society for Geomorphology

Chris Fogwill, an Australian paleoclimatologist and geologist, offers some helpful context in the Sydney Morning Herald on the process by which "pingos," ice formations in permafrost landscapes, transform into lakes.

The British Society for Geomorphology has produced a helpful diagram (at right) showing how this works. Click here for a larger version.

Addendum | Other big holes — mostly familiar sinkholes — have made the news off and on, including the giant hole generated when a salt mine collapsed in Louisiana, one that swallowed some vintage Corvettes in Kentucky and the extremely unnerving orifice in Guatemala City that I covered in 2010. Here's an aerial view of that hole:

Photo A sinkhole formed in Guatemala City in 2010.Credit Government of Guatemala

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Dot Earth Blog: Scientists Begin to Demystify Hole Found in Siberian Permafrost

After a flood of speculation — meteorite collision, methane explosion related to gas drilling, UFO — following the discovery of a gaping crater in the permafrost near big gas fields on the Yamal peninsula in Siberia, scientists are starting to offer more informed views.

Photo A view from the edge of a crater – about 100 feet across – that has opened in Siberian permafrost.Credit Marya Zulinova, press service of the Governor YaNAO

The Siberian Times, the source of initial aerial images and video, has posted the first article citing scientists at the scene. Here are some excerpts.

Photo Scientists are studying a hole discovered in Siberian permafrost.Credit Marya Zulinova, press service of the Governor YaNAO

The crater is smaller than initial reports:

Andrey Plekhanov, Senior Researcher at the State Scientific Centre of Arctic Research, said: "The crater has more of an oval than a circular shape, it makes it harder to calculate the exact diameter. As of now our estimates is about thirty metres."

Here's more from Plekharov, on a possible connection to the warming climate:

"Could it be linked to the global warming? We have to continue our research to answer this question. Two previous summers – years 2012 and 2013 were relatively hot for Yamal, perhaps this has somehow influenced the formation of the crater. But we have to do our tests and research first and then say it more definitively."

He also rebutted speculation that the black marks around the perimeter indicated a fiery explosion had taken place (one example):

"For now we can say for sure that under the influence of internal processes there was an ejection in the permafrost. I want to stress that it was not an explosion, but an ejection, so there was no heat released as it happened."

Earlier scientists were sure there was burning visible on the sides of the crater.

"I also want to recall a theory that our scientists worked on in the 1980s — it has been left and then forgotten for a number of years. The theory was that the number of Yamal lakes formed because of exactly such natural process happening in the permafrost.

Such kind of processes were taking place about 8,000 years ago. Perhaps they are repeating nowadays. If this theory is confirmed, we can say that we have witnessed a unique natural process that formed the unusual landscape of Yamal peninsula."

Photo A diagram from the British Society for Geomorphology explains the formation of a pingo, a hill formed around a buried lump of ice in regions with frozen ground, or permafrost.Credit British Society for Geomorphology

Chris Fogwill, an Australian paleoclimatologist and geologist, offers some helpful context in the Sydney Morning Herald on the process by which "pingos," ice formations in permafrost landscapes, transform into lakes.

The British Society for Geomorphology has produced a helpful diagram (at right) showing how this works. Click here for a larger version.

Addendum | Other big holes — mostly familiar sinkholes — have made the news off and on, including the giant hole generated when a salt mine collapsed in Louisiana, one that swallowed some vintage Corvettes in Kentucky and the extremely unnerving orifice in Guatemala City that I covered in 2010. Here's an aerial view of that hole:

Photo A sinkhole formed in Guatemala City in 2010.Credit Government of Guatemala

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Well: A Vasectomy May Increase Prostate Cancer Risk

Men with vasectomies may be at an increased risk for the most lethal form of prostate cancer, researchers have found. But aggressive cancer nonetheless remains rare in these patients.

Earlier studies had hinted at a connection between vasectomies and prostate cancer. Many experts have dismissed the idea of a link: Men who have vasectomies may receive more medical attention, they said, and therefore may be more likely to receive a diagnosis. The new study, published this month in The Journal of Clinical Oncology, sought to account for that possibility and for other variables.

Researchers at Harvard reviewed data on 49,405 men ages 40 to 75, of whom 12,321 had had vasectomies. They found 6,023 cases of prostate cancer among those men from 1986 to 2010.

The researchers found no association between a vasectomy and low-grade cancers. But men who had had a vasectomy were about 20 percent more likely to develop lethal prostate cancer, compared with those who had not. The incidence was 19 in 1,000 cases, compared with 16 in 1,000, over the 24-year period.

The reason for the increase is unclear, but some experts have speculated that immunological changes, abnormal cell growth or hormonal imbalances following a vasectomy may also affect prostate cancer risk.

Dr. James M. McKiernan, interim chairman of the department of urology at Columbia, said the lack of a clear causal mechanism was a drawback of the new research.

"If someone asked for a vasectomy, I would have to tell them that there is this new data in this regard, but it's not enough for me to change the standard of care," he said. "I would not say that you should avoid vasectomy."

The lead author, Lorelei A. Mucci, an associate professor of epidemiology at the Harvard School of Public Health, emphasized that a vasectomy does not increase the risk for prostate cancer over all. "We're really seeing the association only for advanced state and lethal cancers," she said.

She agreed with Dr. McKiernan that the new data are not a reason to avoid a vasectomy. "Having a vasectomy is a highly personal decision that men should make with their families and discuss with their physicians," she said. "This is one piece of evidence that should be considered."

A version of this article appears in print on 07/18/2014, on page A13 of the NewYork edition with the headline: Study Links Vasectomies to Lethal Cancer Risk.

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Well: A Vasectomy May Increase Prostate Cancer Risk

Men with vasectomies may be at an increased risk for the most lethal form of prostate cancer, researchers have found. But aggressive cancer nonetheless remains rare in these patients.

Earlier studies had hinted at a connection between vasectomies and prostate cancer. Many experts have dismissed the idea of a link: Men who have vasectomies may receive more medical attention, they said, and therefore may be more likely to receive a diagnosis. The new study, published this month in The Journal of Clinical Oncology, sought to account for that possibility and for other variables.

Researchers at Harvard reviewed data on 49,405 men ages 40 to 75, of whom 12,321 had had vasectomies. They found 6,023 cases of prostate cancer among those men from 1986 to 2010.

The researchers found no association between a vasectomy and low-grade cancers. But men who had had a vasectomy were about 20 percent more likely to develop lethal prostate cancer, compared with those who had not. The incidence was 19 in 1,000 cases, compared with 16 in 1,000, over the 24-year period.

The reason for the increase is unclear, but some experts have speculated that immunological changes, abnormal cell growth or hormonal imbalances following a vasectomy may also affect prostate cancer risk.

Dr. James M. McKiernan, interim chairman of the department of urology at Columbia, said the lack of a clear causal mechanism was a drawback of the new research.

"If someone asked for a vasectomy, I would have to tell them that there is this new data in this regard, but it's not enough for me to change the standard of care," he said. "I would not say that you should avoid vasectomy."

The lead author, Lorelei A. Mucci, an associate professor of epidemiology at the Harvard School of Public Health, emphasized that a vasectomy does not increase the risk for prostate cancer over all. "We're really seeing the association only for advanced state and lethal cancers," she said.

She agreed with Dr. McKiernan that the new data are not a reason to avoid a vasectomy. "Having a vasectomy is a highly personal decision that men should make with their families and discuss with their physicians," she said. "This is one piece of evidence that should be considered."

A version of this article appears in print on 07/18/2014, on page A13 of the NewYork edition with the headline: Study Links Vasectomies to Lethal Cancer Risk .

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