research

Primary Prevention of Cardiovascular Disease with a Mediterranean Diet

ImageIn a recent article published in New England Journal of Medicine, Ramón Estruch and his colleagues present results of a multicenter trial in Spain conducted to evaluate the effects of a Mediterranean diet on myocardial infarction, stroke or death from cardiovascular causes in subjects who were at high cardiovascular risk, but with no cardiovascular disease at enrollment. Participants were randomly assigned to one of three diets: a Mediterranean diet supplemented with extra-virgin olive oil, a Mediterranean diet supplemented with mixed nuts, or a control diet (advised to reduce dietary fat). The results of an interim analysis were so overwhelming that the trial was stopped after a median follow-up of 4.8 years.

Study enrolled 7,447 persons with an age range of 55 to 80. Severe cardiovascular events occurred in 288 participants.  More severe events occurred in control group (109) then in the  group assigned to a Mediterranean diet with extra virgin olive oil (96 events) and the group assigned to a Mediterranean diet with nuts (83 events), respectively.  It represented a 30% reduction for the groups with Mediterranean diet in comparison to the control group.

Researchers concluded that “among persons at high cardiovascular risk, a Mediterranean diet supplemented with extra virgin olive oil or nuts reduced the incidence of major cardiovascular events.”

How your diet compares to Mediterranean-style diet? Check it here:

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Estruch R, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet.  NEJM, 2013; 368 (14):1279-1290

Post written by: Petar Denoble, MD, D.Sc.

Obesity, The Heart & Diving

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How does obesity affect your heart and why can obese divers develop heart trouble at apparently low level of exertion?

Obesity is an escalating problem and is linked to a spectrum of cardiac dysfunctions that affect feeling of wellbeing, physical fitness and longevity. In a recent review paper Rider O.J. et al, summarize current knowledge about how obesity affects the heart. The most notable fact is the change of source of the fuel from which the heart derives its energy. By excluding glucose and relying mostly on fatty acids, the energy process becomes less efficient and the heart needs more oxygen for the same level of work. In the long run, lipids become toxic for heart cells and lead to structural changes and weakening of the heart muscles, which is disabling and life threatening. In case of divers who feel fit enough to dive, however, the danger comes from the increased needs of heart for oxygen even at rest. In some cases, even a small increase in exercise level may cause a significant hypoxia of heart muscles which can lead to major troubles.

The good thing is that the problem can be improved by moderate weight loss. However, weight regulation should be started sooner rather than later when changes may become irreversible.

Read the full paper: OJ Rider, P Cox, D Tyler, K Clarke and S Neubauer. Myocardial substrate metabolism in obesity. International Journal of Obesity (2013) 37, 972–979; doi:10.1038/ijo.2012.170; published online 16 October 2012

Learn more from DAN FAQs: Healthy But Overweight

Post written by: Petar Denoble, MD, D.Sc.

Four Healthy Lifestyle Behaviors Slow Down Progression of Atherosclerosis and Lower Risk of Death

Gabriella FabbriThe Multi-Ethnic Study of Atherosclerosis (MESA) included 6,229 US adults aged 44 to 84. All patients were given one point for each of four behaviors they had option to follow: a Mediterranean-style diet, 150 minutes of moderate-intensity physical activity per week, maintaining a healthy body-mass index (BMI), and not smoking. All participants also underwent coronary artery calcium screening at baseline and three years later.

People with higher score (healthier lifestyle) had slower progression of atherosclerosis and 80% less risk of death in the observed period. Each of the healthy behaviors contributed independently to better outcome.

Of the behaviors investigated, however, smoking was the most devastating. Subjects who exercised, ate healthily and maintained normal weight, but smoked, were still worse off than people who did nothing else right but stayed away from cigarettes. Not smoking is the best individual thing people (including scuba divers) can do for their health.

Read full paper: Ahmed HM, Blaha MJ, Nasir K, et al. Low-risk lifestyle, coronary calcium, cardiovascular events, and mortality: results from MESA. Am J Epidemiol 2013; DOI:10.1093/aje/kws453. Available at: http://aje.oxfordjournals.org.

Learn more about cardiovascular health.

Post written by: Petar Denoble, MD, D.Sc.

Microparticles and DCS

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Two studies presented by Steven Thom, one with divers and the other with isolated cells, indicate a role of inert gas under pressure in nitric oxide dependent oxidative stress response which results with microparticles (MP) and inflammation. Microparticles are linked to intravascular bubbles and the cell study seems to indicate that MPs come first and bubbles after (chicken or the egg). The human study provided less obvious answers. While this represents significant progress in elucidating cellular mechanisms involved in decompression sickness, it is far from a straight forward answer. DAN contributed to this study in collaboration with University of Split, Croatia. Sixteen divers volunteered in four dives each and provided blood samples before and after their dives. DAN specialists monitored their heart rate during the dive using an underwater ecg monitor and the presence of venous gas emboli postdive using echocardiography. Additional blood samples have been collected during field studies at Innerspace, a technical diving event in Grand Cayman. Analysis of this data is pending.

The full paper “Microparticle production, neutrophil activation, and intravascular bubbles following open-water SCUBA diving” is available online.

Post written by: Petar Denoble, MD, D.Sc.

DAN Investigates Implanted Cardiac Devices: Volunteers Needed

ImageIn a recent divers’ health survey that DAN conducted, 25 participants, or one in 200, reported having an implanted pacemaker device. The median age of divers with implanted devices was 64 (39 to 90) years and 95% were male. We did not anticipate this and the survey did not ask about reasons for pacemaker implants, but we have learned something about their health status.

  • About 64% active divers with pacemakers were either overweight or obese.
  • 22 reported that they regularly participate in vigorous exercise such as running, biking, swimming, weightlifting, etc.
  • Half were diagnosed with hypercholesterolemia, 9 with hypertension and 4 with diabetes.
  •  Few still indulge in some high risk habits such as heavy drinking and tobacco smoking.
  • When asked to describe their general health, one participant answered it was excellent, 12 very good, 10 good, and one diver said that his health was fair or poor.

Five of the respondents with implanted pacemakers had basic certifications, 16 had advanced and four held instructor-level diving certifications. In terms of diving habits, the respondents with implanted pacemakers reported they:

  • Perform about 30 dives per year (median)
  • Have been active divers for an average of 20 years
  • Have logged a median of 460 total lifetime dives per diver.

Divers with pacemakers don’t seem to be less active than other divers, but we did not explore the circumstances and severity of their dives. We did not ask about specific symptoms or manifestations related to underlying conditions for which they received the pacemaker nor about possible unwanted side effects of pacemakers.

 Volunteers with Pacemakers Needed

This is why DAN designed a new study to learn about specific issues experienced by divers with pacemakers choosing to dive with or without medical clearance. DAN is looking for volunteers to participate in the “Diving Experience of Divers with Implanted Cardiac Devices” study, which consists of an online survey that takes approximately 10 minutes to complete, in addition to a possible follow-up interview if clarification is needed. If you would like to participate in this investigative study, ongoing through August* 2013, please contact DAN Research (919-684-2948 or research@dan.org). Participants will not be compensated for participation.

Post written by: Petar Denoble, MD, D.Sc.

*NOTE: This study has been extended through November 2013.

Deep capability or deep trouble?

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Dr. Simon Mitchell gave an outstanding plenary presentation at the UHMS Annual Scientific Meeting. As a current rebreather diver, he recognizes how much he can do using rebreather, as well as the risks associated with such complex, high-maintenance machine. Divers must be knowledgeable, skilled and disciplined. With new models of rebreathers that target average diver (“recreational rebreathers”) we must do more to prevent injuries, some of which are caused by unsafe human behavior, errors and omissions and other by lack of recognizing predictable machine failure (oxygen cell failure, for example). Simon stressed the conclusions of Rebreather Forum 3.0 (RF3) and the need to use checklists. Checklists should be cleverly designed and printed out, not just mnemonics. It is essential for proper dive leadership to foster a culture of safety in the diving community. I hope you will have opportunity to attend Simon’s presentation at some of dive shows scheduled in the future. In the meantime, here are a few of his lectures from RF3.

CCR Physiology

Anatomy of a CCR Dive

Discussion and Consensus

Post written by: Petar Denoble, MD, D.Sc.

DAN at UHMS: A Recap

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At the Undersea Hyperbaric Medical Society (UHMS) Annual Scientific Meeting, DAN produced six papers, two collaborative papers and funded two more. With additional five papers from International DAN organizations – DAN contributed approximately one-third of the diving medicine presented at the meeting.

I gave an oral presentation about effectiveness of predive checklists, with Shabbar Ranapurwala, doctoral student in epidemiology at UNC as a first author. The paper is coming, but let me tell you in confidentiality, checklists work, even in diving. It was confirmed in a randomized trial conducted in three dive resorts. Volunteers received either a predive checklist and a postdive report (the intervention group) or the postdive report only (the control group). Divers who received the predive checklist experienced fewer mishaps during the dive than divers who did not receive it. Divers in control group were not prohibited from using their own checklists nor were they reminded to do so. The reduced number of mishaps in the intervention group indicates the effectiveness of predive checklists in prevention of accidents and a value of reminding divers to use it.

To learn more, read “Checklists: Keys to safer diving?”

Post written by:

Petar Denoble, MD, D.Sc.

Dr. Petar Denoble is the Vice President of DAN Medical Research. After graduating from medical school, Dr. Denoble joined the Navy in the former Yugoslavia and specialized in naval and diving medicine. For 13 years he was involved with training, supervision and treatment of divers in open circuit, closed circuit, deep bounce and saturation diving. His doctoral thesis focused on studying oxygen consumption in underwater swimming. He has been at DAN for 20 years where he has been involved in the development of the largest database of exposure and outcomes in recreational diving, the monitoring of diving injuries and the study, treatment and prevention of fatal outcomes and long-term consequences of diving accidents.