Vitamin D is a group of fat-soluble steroid-like biochemicals that have one known responsibility in human health–enhancing intestinal absorption of calcium and phosphate, minerals which are necessary for bone development and bone health. In humans, the most important D vitamins are vitamin D3 and vitamin D2, both of which can be ingested from dietary sources, including fishes, milk products, and many other foods. However, the body can synthesize vitamin D’s in the skin when exposure to sunlight is adequate. Because humans can produce their own vitamin D, it is not strictly considered an essential dietary vitamin, which are vitamins that cannot be synthesized in sufficient quantities by an organism, and must be obtained from its diet.
Even though supplementation is necessary for people who aren’t receiving adequate levels of vitamin D through either sun exposure or diet, excessive intake of the vitamin causes a condition called hypervitaminosis D. Excessive vitamin D can lead to acute problems, like excess thirst or increased urination, but over a long-term can lead to heart disease and other chronic conditions.
According to study author Dr. Ramanan Kumareswaran, physicians have known that patients tend to need more ICD shocks during flu season, and wanted to investigate ways of reducing this need to rely on the device.
The study surveyed 229 patients who had come in for appointments related to their ICD care from September through November 2011. Of those patients, 179 (78%) reported that they had received the influenza vaccination in the previous year. Patients who received the influenza vaccine were older than those who did not (70.8 vs. 64.8 years, P=0.0005). Finally, there was no difference in the prevalence of coronary artery disease, diabetes, renal disease, and prior stroke in patients the vaccinated and un vaccinated patients.
Some of the results of the survey were:
Patients who received the flu vaccine were more likely to reject statements such as, “The Flu shot is not effective” and “The Flu shot will make me sick” compared to individuals not receiving the influenza vaccine.
Vaccinated individuals also planned to obtain the influenza vaccine in the upcoming year.
Thirty nine (17.0%) individuals in the overall cohort received at least one ICD therapy during the two pre-defined periods – 10.6% who received the influenza vaccine received at least 1 ICD therapy during influenza season compared to 13.7% who did NOT receive the influenza vaccine (P=NS).
About 13.7% of the unvaccinated patients experienced at least one ICD therapy (meaning that the ICD device had to adjust the heart rate) during the flu season compared to the 10.6% of patients who were vaccinated. This wasn’t a significant difference. However, the average number of ICD therapies per person during influenza season was greater in individuals not receiving the influenza vaccination (0.45 therapies) compared to individuals who did receive the influenza (0.14 therapies).
“What is interesting is that if this is consistent over time, it could be of significant benefit to our patient population who already have compromised survival to start with,” wrote Dr. Sheldon Singh, one of the study’s authors.
The authors concluded:
A large proportion of patients with ICDs receive the influenza vaccine. Receipt of the influenza vaccine may be associated with a reduction in ICD therapies during influenza season.
Now, as I’ve said with the other study, from the same Canadian Cardiovascular Congress meeting, that showed that a link between getting the flu vaccination and reduced cardiovascular events, these studies are not peer reviewed. They aren’t published yet in journals. They haven’t been repeated by other researchers. But the study seems to be sound, and it is a very sound argument for getting the flu vaccination if you have serious cardiovascular issues.
In addition to preventing the disease, the flu vaccination may have a more important benefit to those who get the shot. Dr. Jacob Udell, a cardiologist at Women’s College Hospital and the University of Toronto, looked at published clinical trials on flu vaccinations, dating back to the 1960s, examining the vaccine’s effect on cardiovascular events. Dr. Udell presented his meta-review results at the 2012 Canadian Cardiovascular Congress on October 28 2012.
The combined studies examined a total of 3227 patients, with an equal split between patients with and without heart disease. Half of the patients were randomly assigned to receive flu vaccine, and those that did not received a placebo. Four randomized controlled trials of moderate quality conducted between 1994-2008 met inclusion criteria. Here are some of the most important results:
An approximate 50 per cent reduction in the risk of a major cardiac event (heart attack, stroke, or cardiac death) compared with placebo after one year of follow-up.
A similar trend was seen for the flu vaccine reducing death from any cause (approximately 40 per cent).
The influenza vaccine reduced cardiovascular events and cardiovascular death in people with or without heart disease.
The study concluded:
Influenza vaccine reduced non-fatal CV events and may reduce sudden CV death in patients with and without CVD. However, the very low number of observed CV events and important design limitations among these RCTs strongly limit their validity and make it challenging to draw a definitive conclusion. A large, adequately powered, international multicenter RCT testing the efficacy of influenza vaccine to reduce incident and recurrent CV events is prudent to confirm these findings.
But why would the flu vaccine reduce cardiovascular events? Nelson’s report suggested a couple of very plausible reasons:
“Udell said it may be that when people develop heart disease, some factor ‘tips them over the edge,’ such as plaque clogging arteries, or lower levels of oxygen as a result of the flu.” This is entirely possible, since those with atherosclerosis do have reduced blood flow to heart muscle. And the flu, being much more dangerous than most people believe, could just push someone over the line from having just enough oxygen for their heart muscle, to not enough.
“Dr. Sarah Samaan, a cardiologist and director of the Women’s Cardiovascular Institute at Baylor Heart Hospital in Plano, Texas, said the key to the link may be in reducing inflammation. When someone gets the flu, blood levels of inflammatory substances rise, and inflammation of the blood vessels can trigger heart attacks. ‘This happens because inflammation can make cholesterol plaques in the blood vessels unstable,’ Samaan explained. Unstable plaques are more likely to develop tiny cracks, which can cause blood clots to form. Such clots can block blood flow within arteries, causing a heart attack (if the blood vessel supplies the heart) or a stroke (if the artery feeds the brain), she said.” Again, entirely plausible.
Now, a couple of caveats about this study. First, it’s presented at a conference. Second, it’s not peer-reviewed. I’ll assume that it’s good work, but until it’s peer-reviewed and published in a great journal, it’s at the level of highly provocative. And it’s intensely interesting. But the great thing about meta-reviews is that they are easily repeated, and easily criticized if there’s a problem with the statistical analysis, so in light of that, I have high confidence in the quality of these results.
The 50% reduction in cardiovascular events is both clinically relevant, and may be higher than what will be seen in future randomized trials. But even if it’s 40%, 30%, or even 10%, that’s an amazing benefit of the flu vaccine for individuals at risk for cardiovascular events. The thing is that although a lot of people know that they are at risk, they have diabetes or are overweight, many people are unaware of their cardiovascular risks. They may have untreated hypertension. Or atrial fibrillations. Or any number of diseases where the risks of cardiovascular events are high, and can reduce the risk by a significant amount just by a simple and safe flu vaccination. And don’t listen to those myths about the flu vaccine, they just aren’t true. No, they aren’t true.
Vaccines save lives. And they might keep you from getting a heart attack!