Friday, May 22, 2015

Grip Strength and Cardiovascular Disease Risk

An interesting new study published in The Lancet adds additional evidence to the hypothesis that reduced muscular strength is associated with an increased risk of cardiovascular disease. The study determined the grip strength of nearly 140,000 men between the ages of 35 and 70 years, in 17 countries. Then they followed them for a median of four years, during which time 3,379 of the men (2%) died.

After controlling for other variables such as age, there was a positive association between grip strength and death from cardiovascular disease, including both myocardial infarction (heart attack) and stroke. Specifically, every 11-lb reduction in grip strength was associated with a 17% increase in death from cardiovascular disease. Grip strength was even a stronger predictor of death from cardiovascular disease than was systolic blood pressure. There was no association between grip strength and the risks of diabetes, hospital admissions for respiratory disease, or accidents.

The authors suggest that grip strength may be a simple, inexpensive, and quick way to categorize (in very general terms) a person's risk of death from cardiovascular disease. But don't read too much into this. An association between grip strength and risk of cardiovascular disease does not mean that reduced grip strength is the cause of the increased cardiovascular risk. It's just a useful predictive tool, nothing more.

Thursday, May 14, 2015

Chinese Scientists Genetically Modify Human Embryos

Well, we knew it was bound to happen sooner or later, regardless of whether people think it's a good idea. Chinese scientists tried recently to modify the genes of human embryos. It was just an experiment and it didn't work this time, but who's to stop them or someone else from trying again? Had they been successful, the genetic modifications could have been passed on from generation to generation.

In their experiment, the Chinese researchers used 85 human embryos left over from in vitro fertilization techniques. Using an advanced DNA editing technique called CRISPR, they tried to cut out a gene and insert another in its place. All 85 attempts failed. In nearly every case either the gene was not edited properly or the embryo died.

The ultimate goal of being able to modify a human's genome would be to be able to eradicate certain human genetic diseases. But a lot of people are squeamish about trying to modify the genes of humans. Aside from the obvious risk of something going wrong (as it did with all 85 of the attempts by the Chinese scientists), what's to stop the technique from being used for all sorts of other modifications of the human genome, beyond just eradicating certain diseases? Most scientists are not convinced the technique should ever be used, even if it seems to be likely that it could be done successfully. But almost for certain, others will try. The time to start thinking about it is now, not after someone actually does successfully modify a the genes in a human embryo.

The paper by the Chinese scientists is difficult to read, but here it is if you'd like to try. More about the CRISPR technique can be found here.

Monday, May 11, 2015

Type 2 Diabetes and Sweetened Drinks

We've all heard that type 2 diabetes is on the rise, and that one of the suspected reasons is the number of sweetened drinks we consume these days. But how many is too many, and would it do any good to cut back?

A new British study offers a tantalizing clue, although it's a bit of a "soft" study because it relies only on self-reports of dietary consumption. The study asked over 25,000 British adults about their consumption of sweetened and unsweetened drinks of all kinds, and then tracked their development of type 2 diabetes over 11 years. After adjusting for obesity, and the results showed that reducing consumption of sweetened drinks to less than 2% of total caloric intake could reduce the incidence of diabetes by 15%.

That's fine, but I certainly wouldn't know what 2% of my total caloric intake per day is, in terms of number of sweetened drinks. So how about this? Substituting just one serving/day of water or unsweetened tea/coffee for a sweetened drink was associated with a 14-25% reduction in the incidence of diabetes. Just one serving.

It's something to think about.

Sunday, May 3, 2015

Global Warming and Moderate Weather Events

The evidence continues to accumulate that global warming will lead to climate change; specifically, that extreme weather events will become more common. And now there's yet more evidence. The authors of a recent paper looked at past incidences of more moderate events, such as daily heat waves and precipitation events large enough to occur once every three years. Then, using a climate model, they predicted the number of such events in the future depending on the extent of global warming.

According to their model, so far global warming hasn't had much of an effect on moderate precipitation events. However, if global warming increases to 2o C we can expect the number of moderately heavy precipitation events to increase by about 65%.

The effect of global warming on moderate heat waves, however, is much worse. Already, the 0.85o C rise in global temperatures since pre-industrial times has increased the number of moderately hot days by about 5-fold. If global warming rises to 2o C we can expect another 5-fold increase in hot days.

Of course, predictions about the future are based on climate models; models that are developed based on past experience. Predictions may or may not come to pass. But climate models are getting better every year; we ignore them at our peril.

Friday, May 1, 2015

Global warming, climate change, and species extinctions

In the latest study of the effect that global warming and climate change may have on species extinctions, a study from the University of Connecticut concludes that up to one in six species may be at risk of extinction, depending in the amount of global warming that actually occurs. The study is what is called a meta-analysis; it combined and summarized the data from all of the available global warming -species extinction studies available that met certain criteria of relevance and quality - 131 studies in all.

The results of the study suggest that only 5% of species would become extinct if global warming could be kept to the international agreed-upon target of just 2 degrees centigrade above pre-industrial levels. But virtually no one believes now that we can keep global warming to that limit, given our failure to curb global warming so far. Many of the individual studies summarized in the present meta-analysis predict global warming of more than 4 degrees centigrade, leading to the higher estimate of 1 in 6 species at risk of extinction (about 16%). Most of the extinctions will occur in the tropics, according to the analysis.

Current climate change models predict only what might happen in the time period of decades or centuries. Extinctions might be much higher if higher global temperatures were to persist for tens of thousands of years. Indeed, some scientists think we may be entering a prolonged period that will become the sixth mass extinction experienced by Earth over its 4 billion life span so far.

Many species are likely to be affected by global warming and climate change, even if they do not become extinct. Species may undergo substantial changes in populations, range, and interactions with other species, for example. The good news is that over prolonged periods of time (thousands to millions of years), evolution will continue and species will adapt and change. Life will go on, though whether humans will still be here is anybody's guess.

Sunday, April 26, 2015

A Former Anti-GMO Activist Becomes a GMO Supporter

A former campaigner against genetically modified organisms (GMOs) now says that he supports GMOs. Dr. Mark Lynas, a researcher at the Cornell Alliance for Science who by his own admission once participated in vandalizing field trials of GMO plants in Europe, writes that he feels compelled to reverse his position after coming to the conclusion that GMOs are completely safe to eat and that they offer benefits to society in terms of food security and environmental protection. But don't just believe me; read what he has to say, in his own words.

Saturday, April 25, 2015

The FTC Sues Two Marketers of Melanoma Detection Apps

The Federal Trade Commission (FTC), the federal agency whose mission is to protect consumers from misleading or false advertising, filed a lawsuit and reached a settlement with the marketers of two smartphone apps who claimed that their apps could calculate the risk of a mole being a melanoma. According to the FTC, that's akin to offering medical advice. According to the FTC, the companies cannot offer medical advice "unless the representation is truthful, not misleading, and supported by competent and reliable scientific evidence in the form of human clinical testing" of the device.

This raises an interesting question. Who (which government agency) is responsible for oversight of cellphone apps that appear to cross the line by offering medical advice? Are cellphone apps communication devices that should be regulated by the FTC (as was done in this case), or in a health-related context should they be called medical devices, and therefore regulated by the Food and Drug Administration (FDA)? At the moment no federal regulatory agency is clearly responsible, and so the first apps have gone largely unregulated. Until the FTC stepped in, that is.