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Recently some studies have found that a diminished sense of smell occurs in persons with mild cognitive impairment and Alzheimer's disease. Doctors have long observed that patients with Alzheimer's frequently complain that food doesn't taste good anymore (because they can't smell what they are eating). This is because odor signals from the nose are processed in areas of the brain that are among the first to be affected by Alzheimer's disease. It is thought that as dementia starts and progresses, the parts of the brain that distinguish odors start to deteriorate.

This is why various odor tests have been devised. One such odor test (used in the following study) is called "Sniffin Sticks", which tests for 16 odors such as orange, peppermint, leather, banana, garlic, rose, fish, and coffee. However, note that other degenerative brain diseases (including Parkinson's) can also affect odor detection, and the ability to smell can be diminished by smoking, certain head injuries, and even normal aging. From Medical Xpress:

Study confirms 'sniff test' may be useful in diagnosing early Alzheimer's disease

Tests that measure the sense of smell may soon become common in neurologists' offices. Scientists have been finding increasing evidence that the sense of smell declines sharply in the early stages of Alzheimer's, and now a new study from the Perelman School of Medicine at the University of Pennsylvania published today in the Journal of Alzheimer's Disease confirms that administering a simple "sniff test" can enhance the accuracy of diagnosing this dreaded disease. The sniff test also appears to be useful for diagnosing a pre-dementia condition called mild cognitive impairment (MCI), which often progresses to Alzheimer's dementia within a few years.

Roalf and his colleagues used a simple, commercially available test known as the Sniffin' Sticks Odor Identification Test, in which subjects must try to identify 16 different odors. They administered the sniff test, and a standard cognitive test (the Montreal Cognitive Assessment), to 728 elderly people. The subjects had already been evaluated by doctors at Penn with an array of neurological methods, and according to expert consensus had been placed in one of three categories: "healthy older adult," "mild cognitive impairment," or "Alzheimer's dementia." Roalf and his team used the results from the cognitive test alone, or combined with the sniff test, to see how well they identified subjects in each category.

As researchers report, the sniff test added significantly to diagnostic accuracy when combined with the cognitive test. For example, the cognitive test alone correctly classified only 75 percent of people with MCI, but that figure rose to 87 percent when the sniff test results were added. Combining the two tests also enabled more accurate identification of healthy older adults and those with Alzheimer's dementia. The combination even boosted accuracy in assigning people to milder or more advanced categories of MCI.

Prompted by prior studies that have linked a weakening sense of smell to Alzheimer's, doctors in a few larger dementia clinics already have begun to use smell tests in their assessments of elderly patients. Part of the reason the practice has not yet become common is that the tests that seem most useful take too long to administer. 

People are living longer these days, but the desire is to age with mental faculties intact. Thus it is great to find research that looks at how one can increase the odds of not having cognitive problems or dementia in old age. The research here suggests several things one can do, starting in middle-age, that may help in delaying thinking and memory problems: participating in arts, crafts, socializing, and computer activities. The lead researcher Dr. Roberts said: "The key point we want to get across is that you need to start these activities early"....if you start these activities earlier, perhaps in your 20s, "keep doing them throughout your life; don't stop as you get older." Note that: Mild cognitive impairment (MCI) is an intermediate stage between the expected cognitive decline of normal aging and the more serious decline of dementia. It can involve problems with memory, language, thinking and judgment that are greater than normal age-related changes. From Medical Xpress:

Can arts, crafts and computer use preserve your memory?

People who participate in arts and craft activities and who socialize in middle and old age may delay the development in very old age of the thinking and memory problems that often lead to dementia, according to a new study published in the April 8, 2015, online issue of Neurology.

People age 85 and older make up the fastest growing age group in the United States and worldwide."As millions of older US adults are reaching the age where they may experience these memory and thinking problem called Mild Cognitive Impairment (MCI), it is important we look to find lifestyle changes that may stave off the condition," said study author Rosebud Roberts, MB, ChB, MS, of Mayo Clinic in Rochester, Minn. and a member of the American Academy of Neurology. "Our study supports the idea that engaging the mind may protect neurons, or the building blocks of the brain, from dying, stimulate growth of new neurons, or may help recruit new neurons to maintain cognitive activities in old age."

The study involved 256 people with an average age of 87 who were free of memory and thinking problems at the start of the study. The participants reported their participation in arts, such as painting, drawing and sculpting; crafts, like woodworking, pottery, ceramics, quilting, quilting and sewing; social activities, such as going to the theater, movies, concerts, socializing with friends, book clubs, Bible study and travel; and computer activities such as using the Internet, computer games, conducting web searches and online purchases.

After an average of four years, 121 people developed mild cognitive impairment. Participants who engaged in arts in both middle and old age were 73 percent less likely to develop MCI than those who did not report engaging in artistic activities. Those who crafted in middle and old age were 45 percent less likely to develop MCI and people who socialized in middle and old age were 55 percent less likely to develop MCI compared to those who did not engage in like activities. Computer use in later life was associated with a 53 percent reduced risk of MCI.

On the other hand, risk factors such as having the APOE gene, having high blood pressure in middle age, depression and risk factors related to blood vessels increased the risk of developing MCI.