Dear Doctor: I know that colonoscopies are more thorough than the at-home DNA stool test for colon cancer. But how much better? I have such a terrible time with anesthesia and gas. Both make me nauseated for several days. No one in my family has ever had any colon problems or polyps. I'd really like to pass, if possible.

Dear Reader: As we discussed in a previous article, although colonoscopy remains the gold standard in colon cancer screening, it does indeed pose the risk of complications, leading some people to skip the procedure. If you have problems with anesthesia -- which isn't required but makes the procedure more tolerable -- I can understand your additional worry. As for the DNA stool test, known as Cologuard, it's relatively new (approved by the FDA in 2014), but can provide an option in some cases.

Let's take a look at how the test works. It helps to understand that colon cancer arises from a series of genetic changes and alterations in how genes transmit their information. An effective way to detect these genetic markers in stool tests had been unsuccessful until the advent of Cologuard. The test looks at four molecular DNA markers in addition to a highly specific test for hemoglobin in the stool.

A 2014 study published in the New England Journal of Medicine compared the Cologuard test with FIT screening (a test that simply looks for hemoglobin in the stool); 9,989 people had both of the tests and then had a colonoscopy 90 days later. Of the 9,989, 65 people were found to have colon cancer. FIT detected about 73.8 percent of these cancers, while Cologuard detected 92.3 percent. That sounds good, doesn't it? But when it comes to advanced precancerous polyps, Cologuard detected 42.4 percent, while FIT detected only 23.8 percent. For non-cancerous polyps, Cologuard detected only 17.2 percent, while FIT detected 7.6 percent.

The problem in not being able to accurately detect non-cancerous polyps is that such polyps can develop into cancer that goes undetected until the next time you screen for colon cancer, by which point it may be advanced. Currently, the recommendation for Cologuard is to test every three years. Although you could conceivably test more frequently to detect precancerous lesions as they become cancerous, Cologuard has a high false-positive rate of 16.1 percent.

Here's why that matters in practical terms: Each positive result with Cologuard means a patient then must undergo a colonoscopy. So high rates of false positives ultimately lead to more colonoscopies.

Cologuard is a good test for colon cancer, but its inability to find non-cancerous colon polyps, its high false-positive rate and its cost ($599) prevent it from being a great test. It would be a good choice for people who simply cannot undergo a colonoscopy. That includes people with illnesses that increase the complication rate of colonoscopy, such as severe diverticulitis, diabetes, heart failure and cancer, and people over the age of 75.

Remember, you don't have to use anesthesia to undergo a colonoscopy. If you can tolerate the procedure, I would still recommend colonoscopy. It's the best colon cancer screening test for a healthy person.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I always thought Type 1 diabetes developed when you were a child, or not at all. But now they're saying it can happen as an adult, which is very alarming. How do I know if I develop it?

Dear Reader: While there are several different types of diabetes and different pathways through which the disease develops, they all have one basic thing in common -- the body has lost the ability to adequately regulate the levels of glucose in the blood.

When things are working properly, this glucose control is achieved by insulin, a hormone produced by the pancreas. Insulin makes it possible for the body to either use the glucose that enters the blood after digestion, or to store it for future use. Over time, people with chronic high blood glucose levels will face serious health problems like heart disease, kidney disease, nerve damage, eye problems, poor wound healing, foot problems and even stroke.

In Type 2 diabetes, which can develop at any age, the body has either stopped responding to insulin, or no longer produces enough to properly regulate blood sugar and keep it within optimal levels. In Type 1 diabetes, often referred to as "juvenile diabetes," the body's immune system goes haywire and attacks the insulin-producing cells of the pancreas. Genetics is believed to play a role in Type 1 diabetes, and recent research has shown that viruses may also be involved.

Because Type 1 diabetes is an autoimmune disease, the attack on the insulin-producing cells, known as the islets of Langerhans, is a sustained one. Unlike in Type 2 diabetes, which can sometimes be managed through diet and lifestyle changes, there is no middle ground in Type 1 diabetes. The insulin-producing cells of the pancreas are destroyed and in order to keep blood glucose within a safe range, insulin must be introduced to the body at regular intervals.

Type 1 diabetes is most commonly identified in childhood, but according to the National Institutes of Health, up to 25 percent of cases get diagnosed in adults, some as old as 80 or 90. When certain characteristics are present, this type of diabetes is referred to as latent autoimmune diabetes of adults, or LADA.

Symptoms of Type 1 diabetes, which can occur quite suddenly, may include:

-- Extreme thirst that cannot be quenched

-- Frequent urination

-- Lethargy or exhaustion

-- High sugar content in urine

-- Sudden changes to vision

-- An increased appetite

-- Unexpected weight loss

-- A sweet or fruity scent on the breath

-- Loss of consciousness

If you experience any of these symptoms, get in touch with your health care provider right away.

At this time, there is no cure for Type 1 diabetes. However, in the vast majority of cases the disease can be successfully managed with insulin, diet and exercise. And in the meantime, research continues. Of particular interest is the field of immunotherapy, in which gene splicing and gene editing are used to reprogram the immune system's T cells, which attack the pancreas. What would have sounded like science fiction just a decade ago could someday lead to a long-term cure.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I recently read that marriage reduces the risk of mental decline in old age. I'm not sure I buy it. But, assuming it's true, why would that be?

Dear Reader: You're likely referring to a recent study in the journal Neurology, Neurosurgery and Psychiatry that combined data from 15 studies with a total of 812,047 people. In each of the studies, the authors looked at the marital status of participants over age 65 and the overall rate of dementia. Most of the studies were performed in Europe, with the largest -- 750,129 participants -- conducted in Sweden. The average age of all participants was 73 years.

The data did suggest a protective effect from marriage, with lifelong single people having a 42 percent higher risk of dementia than married people, and widowed people having a 20 percent higher risk. The researchers found no differences based on gender.

Interestingly enough, in the primary analysis, divorced individuals had the same rates of dementia as their married counterparts. But, notably, when researchers looked at data from the large Swedish study, they found twice the risk of dementia among divorced people who began the study between the ages 50 and 64 and 1.4 times the risk among divorced people ages 64 to 75.

There's no one good explanation why marriage would benefit brain function. It may be that marriage challenges a person. In the needed conversation between the partners in marriage, there are differences of opinion, a necessity for mental flexibility, and a level of stress that requires people to go outside of their comfort zones and challenge their brains. It also may be that married life leads to social interactions with other couples or with in-laws, which lead to greater human interaction -- even if all of them aren't pleasant.

Obviously, marriage tends to provide greater social support. To know that somebody cares about you can reduce depression and anxiety, which also may lead to a greater desire to take care of yourself both physically and mentally. This self-care, in turn, may help ward off dementia. That could be why being widowed is associated with a greater risk of dementia, compared to being married.

Then there are the health aspects of marriage. Other studies have found that marriage is linked to increased longevity, which suggests that dementia risk may be reduced through a decreased rate of illnesses and habits that can increase the likelihood of dementia.

Ultimately, although marriage may provide a modest benefit in warding off dementia, I would look at this data with a grain of salt. Many people who have never been married, who have been divorced or who are widowed obviously lead long lives without any trace of dementia. Certainly, no one would recommend an unhappy marriage as a possible protective factor against dementia risk.

Further, the recently published data are from older individuals. The study's ultimate conclusion may be applicable to a different world than the one in which we currently live. In this day and age, society is more accepting of a single life; our current world may be stimulating and protective enough on its own.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)