More than 5 million people in the U.S. are living with Alzheimer's disease, the most common form of dementia. There is no cure or prevention for Alzheimer's disease, despite all the research into its causes.
Now a new study spanning 46 years offers some tantalizing clues. Way back in 1968, researchers in Sweden enrolled 191 women 38-60 years old into a study of cardiovascular fitness, as measured by their capacity to exercise on a bicycle until they became so fatigued that they had to stop. Based on their workload achieved, they separated the women into "low", "medium" and "high" fitness groups. Then they followed the women for the next 44 years, looking for signs of dementia, among other health issues. Surprisingly, they found that compared to the "medium" fitness group, those in the "high" fitness group were 88% less likely to develop dementia. Among those who did develop dementia, high fitness delayed the time to onset of dementia by 5 years, compared to the medium fitness group.
A word of caution; these results show a correlation only; they do not prove that high fitness per se is what is reducing the risk of dementia. Perhaps the high fitness group also has a better diet, or just better genetics to begin with. Nevertheless, the results are intriguing, and may point the way to additional research to tease out the actual cause. Anything we can do to solve this baffling and debilitating disease would be welcome.
Thursday, March 29, 2018
Sunday, March 25, 2018
The Origin of Sickle Cell Trait
Tens of millions of people have a genetic mutation in a single allele (one of a pair of genes) that by itself has no outward effect on the person's health, called sickle cell trait. Unfortunately, persons who inherit two copies of the allele (one from each parent) suffers from sickle cell disease, a debilitating condition in which red blood cells cab change shape, or sickle, impeding blood flow and damaging organs.
Typically, a genetic mutation that leads to health problems would be selected against over time by normal evolutionary processes. However, that's not the case for sickle cell trait, because it turns out that inheriting just one copy of the abnormal gene is protective against another disease, malaria. As a result the abnormal gene is selected for, not against, by evolutionary processes, especially in places such as Africa where malaria is common.
But where and when did the mutation arise? The genetic mutation comes in five different haplotypes, or forms, leading some scientists to speculate that the mutation arose independently perhaps as many as five different times. Others have suggested that it arose just once.
In attempt to resolve the dispute, researchers recently studied the genomes of nearly 3,000 people. 156 of them had the mutated gene for sickle cell trait. On close examination of their genomes (the details are beyond the scope of this blog), the researchers concluded that all 156 people had inherited the mutated allele from a single person who lived around 7,300 years ago. That person probably lived in western or central Africa. Case closed, it seems.
Typically, a genetic mutation that leads to health problems would be selected against over time by normal evolutionary processes. However, that's not the case for sickle cell trait, because it turns out that inheriting just one copy of the abnormal gene is protective against another disease, malaria. As a result the abnormal gene is selected for, not against, by evolutionary processes, especially in places such as Africa where malaria is common.
But where and when did the mutation arise? The genetic mutation comes in five different haplotypes, or forms, leading some scientists to speculate that the mutation arose independently perhaps as many as five different times. Others have suggested that it arose just once.
In attempt to resolve the dispute, researchers recently studied the genomes of nearly 3,000 people. 156 of them had the mutated gene for sickle cell trait. On close examination of their genomes (the details are beyond the scope of this blog), the researchers concluded that all 156 people had inherited the mutated allele from a single person who lived around 7,300 years ago. That person probably lived in western or central Africa. Case closed, it seems.
Thursday, March 22, 2018
Rates of STD Infection in the U.S. Continue to Rise
The rates of infection of most STDs rose again in 2016, according to the CDC. Compared to 2015, chlamydia infections were up 4.7%, syphilis infections increased 17.6%, and gonorrhea was up by 18.5%. The increases are part of a trend that started about a decade or so ago.
The only good news is that rates of HIV infection have been trending slightly downward over the past five years. Compared to 2015, the rate of HIV infection declined by 0.1% in 2016.
The dramatic increases in syphilis and gonorrhea infections in 2016 are cause for concern, of course. Sexually active individuals should be aware of these trends and seek to protect themselves accordingly.
The only good news is that rates of HIV infection have been trending slightly downward over the past five years. Compared to 2015, the rate of HIV infection declined by 0.1% in 2016.
The dramatic increases in syphilis and gonorrhea infections in 2016 are cause for concern, of course. Sexually active individuals should be aware of these trends and seek to protect themselves accordingly.
Wednesday, March 21, 2018
Exercise Can Turn Back Time on a Middle-Aged Heart
So... you didn't take care of your body when you were young, and now at middle age you're feeling out of shape and over the hill. You're motivated to make a lifestyle change if it would help, but will it actually do any good at this point?
The good news is that perhaps it will. According to a report in Circulation, just two years of high-intensity exercise improves heart health. In the study, sedentary middle-aged men (mean age 53 years) participated in either a moderate to high intensity aerobic exercise program for two years (the experimental group), or only non-aerobic exercise such as yoga or balance training (the control group). At the end of two years, those who had exercised showed signs of improved heart health, including improved oxygen uptake and a reduced stiffness of the left ventricle. It's as if the clock was turned back on the heart aging process.
Middle age may be the last time that one can improve heart function, however. According to an NPR article, the same improvement is not possible by the time one reaches seventy years of age. The time to get moving is now, not later.
The good news is that perhaps it will. According to a report in Circulation, just two years of high-intensity exercise improves heart health. In the study, sedentary middle-aged men (mean age 53 years) participated in either a moderate to high intensity aerobic exercise program for two years (the experimental group), or only non-aerobic exercise such as yoga or balance training (the control group). At the end of two years, those who had exercised showed signs of improved heart health, including improved oxygen uptake and a reduced stiffness of the left ventricle. It's as if the clock was turned back on the heart aging process.
Middle age may be the last time that one can improve heart function, however. According to an NPR article, the same improvement is not possible by the time one reaches seventy years of age. The time to get moving is now, not later.
Tuesday, March 20, 2018
Herbicides Can Alter the Nutritional Content of Food Crops
Herbicides are widely used commercially to improve crop yields and to reduce the need for hoeing and weeding. But do herbicides affect the nutritional content of food crops? Are organic foods nutritionally different from non-organic foods, and if so, are they better for you? Surprisingly, very little research has been done on this subject.
A research paper published last month in the Journal of Agricultural and Food Chemistry suggests that some common herbicides can indeed change the nutritional content of a food crop (sweet corn). The research team exposed sweet corn to four different herbicides, with or without a commonly used "safener", which helps to protect the corn from herbicide damage. All of the herbicides increased the protein content of the corn slightly, and some of them increased the content of certain minerals (phosphorus, magnesium, manganese, and iron) as well. Several of the herbicides also altered the balance of sugars (fructose/glucose/sucrose) and the amounts of fatty acids.
Whether the effects of herbicides on nutritional content are good or bad is still an open question. All that can be said at the moment is that herbicides can affect the nutritional content of food plants in a myriad of ways.
A lot is still unknown about the effects of agricultural chemicals on food crops, including whether herbicides affect the food's taste. Further research is warranted.
A research paper published last month in the Journal of Agricultural and Food Chemistry suggests that some common herbicides can indeed change the nutritional content of a food crop (sweet corn). The research team exposed sweet corn to four different herbicides, with or without a commonly used "safener", which helps to protect the corn from herbicide damage. All of the herbicides increased the protein content of the corn slightly, and some of them increased the content of certain minerals (phosphorus, magnesium, manganese, and iron) as well. Several of the herbicides also altered the balance of sugars (fructose/glucose/sucrose) and the amounts of fatty acids.
Whether the effects of herbicides on nutritional content are good or bad is still an open question. All that can be said at the moment is that herbicides can affect the nutritional content of food plants in a myriad of ways.
A lot is still unknown about the effects of agricultural chemicals on food crops, including whether herbicides affect the food's taste. Further research is warranted.
Friday, March 9, 2018
Australia May Become the First Country to Eradicate Cervical Cancer
If the current trend continues, Australia may become the first country to virtually eradicate the HPV virus that causes cervical cancer. How did they do it? Health officials credit an aggressive government-financed vaccination campaign begun in 2007 that targeted 12-13 yr.-old girls, combined with a catch-up program to vaccinate older girls and women up to the age of 26 that was completed in 2009. By 2015, 53% of women in the now 18-35-yr.-old age group had been vaccinated. More importantly, rates of HPV infection have dropped from 22.7% to less than 1.5%. That's a 93% decline in HPV infection rates!
Why did HPV infection rates drop so dramatically when only 53% of the women have been vaccinated so far? It's the well-known "herd effect" - when enough people in a population are immune to a transmissible disease organism, it's much harder for the organism to be transmitted from person to person, even though some people are not yet immunized.
Although health officials have not yet seen a dramatic decrease in the number of cases of cervical cancer, that's because it can take years for cervical cancer to develop after HPV infection. At the moment, the number of cases of cervical cancer is just beginning to decline. Nevertheless, officials are confident that with continued aggressive vaccination against HPV, within 30-40 years cervical cancer will be a thing of the past in Australia.
The full HPV vaccination regimen costs about $400 per person in the U.S.; probably less in a country like Australia with a government-sponsored program. Sounds like a pretty good deal to me.
Why did HPV infection rates drop so dramatically when only 53% of the women have been vaccinated so far? It's the well-known "herd effect" - when enough people in a population are immune to a transmissible disease organism, it's much harder for the organism to be transmitted from person to person, even though some people are not yet immunized.
Although health officials have not yet seen a dramatic decrease in the number of cases of cervical cancer, that's because it can take years for cervical cancer to develop after HPV infection. At the moment, the number of cases of cervical cancer is just beginning to decline. Nevertheless, officials are confident that with continued aggressive vaccination against HPV, within 30-40 years cervical cancer will be a thing of the past in Australia.
The full HPV vaccination regimen costs about $400 per person in the U.S.; probably less in a country like Australia with a government-sponsored program. Sounds like a pretty good deal to me.
Thursday, March 8, 2018
A New Risk Factor for Heart Attack and Stroke
Why is it that most patients who have had a stroke or a heart attack don't have any of the normal risk factors, such as high cholesterol or high blood pressure, that are generally associated with cardiovascular risk? The answer, it seems, may be a risk factor that has been missed until now; a condition called clonal hematopoiesis of indeterminate potential, or CHIP.
In essence, CHIP is a condition in which some of the stem cells in bone marrow that initiate the production of white blood cells (WBCs) begin to mutate, resulting in the increased production of white blood cells carrying the mutation. Patients with an increased number of these mutated WBCs in their blood are 40-50% more likely to die of a stroke or a heart attack within 10 years. Apparently, the risk of developing CHIP goes up sharply with age. Although only about 20% of 60-yr-olds have developed CHIP, half of all 80-yr-olds have the condition. It's almost as if CHIP is a normal consequence of aging.
And how might CHIP contribute to cardiovascular disease risk? Researchers have long speculated that chronic inflammation may contribute to the development of blood vessel-blocking atherosclerosis. And its possible that chronic inflammation is initiated by increased numbers of inflammatory WBCs in the blood.
Doctors are not advising their patients to be tested for CHIP yet, because at the moment there is nothing to be done about it even if you do test positive. At least not yet; perhaps some day there will be.
In essence, CHIP is a condition in which some of the stem cells in bone marrow that initiate the production of white blood cells (WBCs) begin to mutate, resulting in the increased production of white blood cells carrying the mutation. Patients with an increased number of these mutated WBCs in their blood are 40-50% more likely to die of a stroke or a heart attack within 10 years. Apparently, the risk of developing CHIP goes up sharply with age. Although only about 20% of 60-yr-olds have developed CHIP, half of all 80-yr-olds have the condition. It's almost as if CHIP is a normal consequence of aging.
And how might CHIP contribute to cardiovascular disease risk? Researchers have long speculated that chronic inflammation may contribute to the development of blood vessel-blocking atherosclerosis. And its possible that chronic inflammation is initiated by increased numbers of inflammatory WBCs in the blood.
Doctors are not advising their patients to be tested for CHIP yet, because at the moment there is nothing to be done about it even if you do test positive. At least not yet; perhaps some day there will be.
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