Multiple sclerosis is a horrible disease afflicting an estimated 400,000 Americans. There is no cure and little understanding of the cause, even though the patterns of MS leave many tantalizing clues.

An experimental drug called BG-12 helps reduce the number of “flare-ups" in the disease, researchers reported on Wednesday -- much like the nine other drugs already approved to treat MS.

MS occurs because the immune system – mostly disease-fighting T-cells – destroy the myelin sheath, the coating on the outside of brain and spinal nerve cells. This doesn’t happen continually, but in separate attacks or flare-ups, often a year or more apart. No part of the brain or spinal cord seems resistant. Although people with MS can appear very healthy, these autoimmune attacks often inflict severe damage.

“MS can affect vision, movement, strength, sensation, bowel, bladder, sexual function, mood, cognition," says Dr. Robert Fox, a neurologist at the Cleveland Clinic who headed the BG-12 study. "Everything the brain does can be impaired from MS.”

Like most autoimmune diseases, it's possible MS is set off by a viral infection. After the infection, the immune system starts to mistake neurons for virus or infected cells and destroys them. The evidence for a viral role comes from studies done in the Orkney, Shetland and Faroe Islands off Scotland. All these islands share similar geography and ethnic makeup. Prior to 1943, the Orkneys and Shetlands had a high incidence of MS, and the Faroe Islands almost none. Then it evened out. The best guess is that the movement of British troops spread a virus.

Despite this and similar other areas that became infected at a certain time, scientists have yet to identify the virus.

There also strong evidence for genetic susceptibility. Much of that comes from the incidence of MS among various ethnic groups. Caucasians have the highest incidence. Some ethic groups have almost no MS. These include the Inuit of Canada, Yakuts of Russia, the Hutterites, a religious group in Montana, Hungarian Romani, Norwegian Lapps, Australian Aborigines and New Zealand Maoris.

Many populations in Africa almost never suffer MS, but when they migrate to Europe or the U.S. their rates go up. Many Asian populations have almost no MS, and for them migration does not seem to increase susceptibility. In general, MS seems to occur far more often in cooler climates than closer to the equator. Also like many autoimmune diseases, hormones seem to play a role. MS occurs about three times as often in women as men — especially for cases diagnosed for people in their 20s, 30s, and 40s.

Scientists have focused on each of these clues. But none has so far yielded the cause or a cure for the disease. And although people with MS have near-average life expectancies, until there are better medications, they will likely end up in a wheelchair with many other disabilities.

 Related stories:

Ann Romney speaks about her MS

New MS drug gets approval

A study out Wednesday suggests that calcium supplements might increase the risk for heart attacks. But this research from Swiss scientists in the British journal Heart is just the type of experiment that often scares people unnecessarily and gives the science of epidemiology a bad name.

The Swiss scientists looked at a group of almost 24,000 people who participated in a European cancer and nutrition study over 11 years. There is the first tip that the research might be less than reliable. The study was set up to look at cancer risk and these scientists are “mining” the data to look for heart disease outcomes. What the researchers unearth is a confusing set of conclusions.  In some people calcium intake seems to protect against heart disease. Indeed in the entire population there was no increase in total heart disease. But among those taking large amounts of supplements, they observe an increased number of heart attacks.

There has been concern for some time that too much calcium supplementation might cause heart disease because heart disease can result from a buildup of calcium in the arteries.  Several studies of the issue have come to differing conclusions.  What is not in doubt is that calcium in the correct amounts is critical for bone heath, but too much can cause health problems, possibly heart disease but for sure a risk of kidney stones and other health problems.

The study, though, should remind people that even though calcium is critical for bone health too much can be a hazard.

As Dr. Ethel Siris of New York-Presbyterian Columbia puts it, "People think more is better in this case in this case more is not better. Enough is enough.”

Getting the right amount of calcium can be a challenge.  The government recommends that adults take 1000 mg a day of calcium and women over 50 take 1200.  But it says no one over 50 should be taking more than 2000 mg a day.

It is easy to get too much calcium -- 22 percent of the adult US population takes calcium supplements.

Many foods have calcium.  A cup of milk, a serving of cheese and a container of yogurt all have more than 300 mg. Some fortified breakfast cereals have as much as 1000 mg per serving.

But for bone health people do need calcium including a supplement. If they are not getting it from food or other sources they need a supplement – just not too much.

By Robert Bazell, NBC News correspondent

Your comments on my Monday posting about the task force’s recommendations on PSA testing are greatly appreciated. 

They were lively, for the most part civilized, and illustrated the complexity of the subject. As the physician in our "Nightly News" report said, “This has been one of the most gut-wrenching aspects of medicine.”

In response to what many people said I want to repeat that these are recommendations made for the entire population based on what the panel sees as the best evidence.  They are intended to serve as a starting point for a conversation between a man and his physician. They are not an absolute declaration about what any one person should do about his health care.

To answer some questions that were raised:

• Some people asked about how the guidelines apply to younger men.  There were no specific recommendations for younger men.  The two big studies of the efficacy of routine testing were done in men in their 50s, 60s and 70s.
• Some asked about guidelines on what to if prostate cancer is detected.  The task force did not discuss that issue.  The panel certainly made no recommendation against treatment.  But its mandate was to assess the utility of routine screening of healthy men.
• As for the question of whether prostate cancer is potentially life threatening, despite Gleason scores and other methods for staging prostate cancer, the issue remains difficult.  Much research is being directed at trying to find a molecular marker that would indicate which prostate cancer poses the greatest threat.
• Others asked why false positives are a bad thing.  False positives -- or in the case of the PSA test even some not-false positives -- can lead to unnecessary treatment, which can have serious side effects.

Click here to read Robert Bazell's earlier piece about the PSA test guidelines. 

Should high school kids get a genetic test for the risk for Alzheimer’s disease before they’re allowed to play football? Two prominent scientists who study both Alzheimer’s and the traumatic brain injury suffered by some football players raise that ethically charged question in an editorial out Wednesday in the journal Science Translational Medicine.

We all carry a gene called APOE which comes in three forms. If we carry one copy of the form called E4, it triples our lifetime risk for Alzheimer’s. About 10 percent of the U.S. population falls in that category. If we have two copies of E4, the lifetime Alzheimer’s risk is 15 times greater. About 2 percent of us have that genetic makeup.

Although the connection between APOE E4 and Alzheimer’s risk has been known for years, few have suggested it as a screening tool because there’s no known way to prevent the mind-robbing disease. But, now as scientists want to test drugs as early as possible as potential methods of preventing Alzheimer’s, APOE is getting more attention, as are brain scans and other techniques that might determine who is at risk.

At the same time, scientists have been finding that football players, boxers and soldiers suffering blast injuries are more likely to develop chronic traumatic encephalopathy (CTE), the form of dementia that can follow a brain injury -- if they have one or two copies of the E4 version of APOE.

Neurologist Dr. Sam Gandy of Mt. Sinai Medical Center in New York and Alzheimer’s researcher Dr. Steven DeKosky of the University of Virginia School of Medicine, Charlottesville, conducted a poll of 49 colleagues. By a 2 to 1 decision their fellow scientists said it is not yet appropriate to test high school students, and by a 3 to 1 ratio they opposed testing military recruits. But few of the scientists dismissed the ideas out of hand.

As the evidence of a connection mounts, testing may become more of an imperative.

There are obvious, enormous ethical difficulties. Telling a 14-year-old that he or she faces an increased lifetime risk of Alzheimer’s could lead to unknowable future strains on individuals and families, as well as a lifetime of difficulty in getting health and life insurance. But if scientists learn how to intervene to prevent the Alzheimer’s, or if the evidence of increased risk from sports or on the battlefield becomes overwhelming, the question may be asked more often.

Robert Bazell is NBC's chief science and medical correspondent. Follow him on Facebook and on Twitter: @RobertBazellNBC.

More from Robert Bazell:

• US assurances on mad cow case may be 'gross oversimplification' 
• Out-of-whack sleep habits can cause diabetes
• Dental X-rays linked to brain tumor risk

Related:

• First Alzheimer's prevention study launched

By Robert Bazell
Chief science and health correspondent
NBC News

Not long ago, statins were jokingly promoted by some doctors with a “put them in the drinking water” argument. Physicians and drug company experts suggested that the ubiquitous cholesterol-lowering drugs -- including Lipitor, Mevacor, Crestor and Zocor -- should be sold over the counter like cold medications, or offered to everyone above a certain age. The medications appeared so beneficial to health and seemed so free of side effects.

But on Tuesday, the Food and Drug Administration issued a new health alert requiring the drugs carry labels warning about confusion and memory loss, elevated blood sugar leading to Type 2 diabetes, and muscle weakness.

“These warnings should put an end to the all the silliness about giving the drugs to everyone,” says Dr. Garret FitzGerald, chairman of pharmacology at the University of Pennsylvania.

Warnings for diabetes, memory loss added to statins

There is no question that statins -- the most profitable and among the most prescribed drugs ever -- have saved or prolonged millions of lives and will continue to do so. Most people at elevated risk for heart disease should be taking statins. The big issue now will center on determining whose risk is low to moderate and may not need medication.

The not-so-well-kept secret is that a daily dose of statin allows millions to eat whatever fatty food they like without worrying how it affects their cholesterol levels. That’s a tempting proposition. At the same time, drug companies find nothing more appealing than a pill that healthy people take daily for the rest of their lives. These two motivations combine to get million on statins who may not need them -- not much of a problem if there are no risks. But now we have evidence there is.

The FDA approved the first statin, Merck’s lovastatin, in 1987. Other companies produced their own versions over the last two decades as evidence of the drugs’ effectiveness continued to accumulate, adding to their popularity.  But, early on, plenty of side effects warnings popped up. 

Every time NBC News reported on statins I would receive many communications from viewers who had suffered the muscle-weakening condition, known as rhabdomyolysis, after taking the medication. When they stopped the drug, their muscles usually returned to normal. Doctors who frequently prescribe statins report that a certain percentage -- the best guess is about ½ to 1 percent -- suffer the muscle problems. That’s a rare occurrence as side effects go, but when many millions are taking the drugs, the numbers add up.

As for elevated blood sugar and memory problems, both conditions have been reported for years, but it is harder to guess how widespread the complications are. In fact, last month, a survey of 150,000 participants in the Women’s Health Initiative -- the government’s gigantic study that ended most hormone replacement -- found that older women taking statins were 48 percent more likely to develop diabetes. (The researchers tried to control for obesity and other risk factors.)

Because most people who take statins tend to be older, they’re already more likely to develop diabetes or memory problems. The only test to accurately measure the risk from statins would be a long, controlled trial of thousands of people at low risk for heart disease where half get the drug and half get a placebo. No drug company will pay for it.   

Astra Zeneca’s Crestor remains the only statin still under patent protection, and it would be foolish for that company to go looking for harmful side effects. The government’s resources for big expensive studies grow ever more scarce. We may never know the true danger, but at least now the drugs have labels telling patients and doctors to be aware of them

Why did the FDA chose to label the drugs now when the danger signs have been around for years? There is no official answer, but the officials in charge of the FDA now have shown far more willingness to be honest about public health risks than many of their recent predecessors.

As for whether you or a loved one should be taking a statin drug: This is certainly not an automatic decision, but definitely a subject for a discussion with your physician. Because of the FDA’s labeling actions that decision should now be far better informed.

By Jane Derenowski
NBC News producer

Part 3: LOOKING BACK TO THE LAND

The last part of the Back to Basics journey took me and NBC's Chief Science Correspondent Robert Bazell to the small town of Sells, Ariz. This is home to the Tohono O'odham Indian Nation. The Nation has recently struggled with alarmingly high rates of type 2 diabetes and obesity, but it is now looking to the past to create a healthier future. 

Years ago, they relied on farming and ate a diet rich in fruits, vegetables, and grains. But along the way, the practice was abandoned along with many traditions.

Now, with the help of Nation elders, young and old alike are returning to the farms and reviving customs such as storytelling, O'odham dance, and singing.

The result: slow but steady progress toward better health and a re-birth of the Tohono O'odham culture.

Learn more about the Back to Basics series.

Part 1: Give kids time to play

Part 2: Take a social media break