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Many procedures require anesthesia, and which of the four types you have can affect your recovery.

If you've ever had a tooth filled without Novocaine, you know the difference anesthesia can make. Anesthesia鈥攚hether it numbs your mouth or puts you into a full sleep鈥攊s designed to keep you comfortable during a procedure that otherwise might be hard to tolerate physically, emotionally, or both. "We have four goals: to see that you have no pain, that you're drowsy or unconscious, that your body is still so that the surgeon can work on it, and that you aren't left with bad memories of the procedure," says Dr. Kristin Schreiber, an anesthesiologist at Harvard-affiliated Brigham and Women's Hospital.

There are four basic kinds of anesthesia鈥攍ocal, which is typically administered to numb a small area; regional, which numbs a larger area, like your hand, arm, or foot; neuraxial (spinal or epidural), which is injected near the spine and numbs the lower half of your body; and general, which works in the brain to render you completely unconscious and unable to sense pain. The type used depends upon the procedure you're having, your state of health, and, often, your preferences.

Researchers from the biotechnology company Biogen have reported that a new drug reduced the amount of amyloid plaques鈥攖he brain deposits associated with dementia鈥攁nd slowed cognitive decline in people with early Alzheimer's disease. They presented the report March 20, 2015, at the International Conference on Alzheimer's and Parkinson's Diseases in Nice, France.

The researchers studied 166 people ages 50 to 90 who had been diagnosed with mild Alzheimer's. The participants were randomly assigned to receive either a placebo or one of four different doses of the drug aducanumab鈥攁n antibody that attaches to amyloid deposits and turns the immune system on them.

Q. Why is my doctor checking me for tuberculosis? I thought that was eradicated long ago

A. It would be wonderful if tuberculosis (TB) had been eradicated long ago, but unfortunately that's not the case. It is true that the annual number of new cases in the United States has been dropping over the past 20 years; in 2013, there were about 9,500 new cases. However, around the world, particularly in developing nations, TB remains a huge problem. In 2013, there were nine million new cases of TB, and 1.5 million deaths from TB, in the world.

Excessive sun exposure can cause damage that shows up many years later.

It may boost the effect of your current medication.

If your weather forecaster warns about a heat wave this summer, take it seriously. A study by Harvard researchers found that people with certain conditions were at an increased risk of winding up in the hospital during periods of high heat. Their work was published Dec. 23, 2014, in The Journal of the American Medical Association.

Researchers analyzed hospitalization rates for specific diseases among 23 million Medicare beneficiaries between 1999 and 2010. What sent older adults to the hospital most often during a heat wave? Heatstroke, fluid and electrolyte disorders, kidney failure, urinary tract infections, and sepsis (a dangerous blood infection). For some diseases, the risk of hospitalization was elevated for up to five days after a heat wave day, suggesting that preventing and treating heat-related illnesses is crucial both during and after a heat wave.

Colonoscopy saves lives, and adequate prep is essential for a successful colonoscopy. New laxative preps are making the process easier to tolerate.

Q. I'm 82 and a landscape painter. Lately the sight in my right eye seems to be affecting my painting, although I can still see well enough to read small print and drive. I have a cataract in that eye. Should I have cataract surgery?

A. A cataract is a thickening and cloudiness of the lens of the eye that is more common as we age. If your eye doctor has recommended that you have the cataract removed, then yes, you should have the surgery, especially if your vision is impaired. The surgery involves taking your lens out and replacing it with an artificial one. Being able to see more clearly will not only help your painting, but it will also reduce your risk of falling. There is even some evidence that people who have cataracts removed live longer than those who don't, possibly because their improved vision allows them to participate more fully in life.

Harvard scientists are getting international attention for their work with breakthrough technology that can edit genes in living cells. Five Harvard experts鈥擠r. George Church of Harvard Medical School, and Drs. Keith Joung, David Liu, Kiran Musunuru, and Derrick Rossi, all of Harvard University鈥攚ere featured speakers in the first-ever CRISPR Congress, held in Boston in February 2015. CRISPR stands for clustered regularly interspaced short palindromic repeats. These are segments of genes that contain repeating sequences of DNA.

The Harvard experts spoke to other scientists about CRISPR, which holds the potential to repair gene mutations, fight disease, and improve food supplies. Harvard researchers have demonstrated that CRISPR may be able to lower cholesterol levels, correct gene mutations, and block HIV infection. "Suddenly anyone can edit any piece of any DNA a thousand times more easily and precisely than before, which is game-changing for gene therapies, organ transplantation, aging reversal, and malaria," says Dr. Church.

Hidden causes of shortness of breath can make the problem tricky to treat.