Update 5/26/16: In a potentially groundbreaking new study this week, researchers from Harvard University found evidence that the build-up of beta amyloid protein in the brains of Alzheimer’s patients may signal an infection, rather than a lack of sleep (as previously thought). The paper, published by the American Association for the Advancement of Science, can be found here.

The first mention of Alzheimer’s disease was by German doctor Aloysius Alzheimer in 1906. A patient, whom Alzheimer referred to as “Auguste,” was presenting with a “peculiar disease.” He knew little about it, recording symptoms such as loss of memory, unfounded suspicions, and loss of cognitive skills.

More than a century later, an estimated 5.1 million Americans are living with Alzheimer’s, which we now know is a degenerative neurological disease. While scientists have made strides in finding out what happens to the brains of people with the disease, why it happens remains a mystery.

In the absence of a known cause or cure, the disease is pervasive, killing more people than breast cancer and prostate cancer combined. Due to the around the clock care that late-stage patients require, it’s also one of the most expensive—costing the U.S. $226 billion in 2015 alone.

The sixth-leading cause of death, Alzheimer’s disease is the only one in the top 10 that cannot be slowed, stopped, or prevented. With this knowledge, scientists are performing many studies to locate the underlying cause and find a possible cure.

Dozens of studies were published on the disease this year, both on potential risk factors and ways to decrease risk. As is true with studies in any field, some are weaker than others, but together they present a compelling sign of progress.

Here are six of the most compelling studies.

Ageism May Increase Risk

In December, a study from researchers at the Baltimore Longitudinal Study of Aging (BLSA) found evidence that negative views about aging could increase your risk of Alzheimer’s. The study centered on the volume of the hippocampus in two groups of men and women—one with negative views of age, the other with positive views.

In the group with negative views of age, the researchers found a “rate of decline in hippocampal volume three times the rate of decline in the positive-age-stereotype group.” Brain shrinkage—specifically in the hippocampal region—is one of the main characteristics of Alzheimer’s.

Another identifier of Alzheimer’s is a buildup of abnormal proteins (“plaques”), which the ageist group presented a higher number of as well.

But the study was not without flaws. With only 52 participants, it doesn’t necessarily prove a causal relationship.

Olive Oil Could Help Reduce Risk

This year science presented further evidence to bolster a long-held theory that a diet heavy in olive oil may help protect the brain from Alzheimer’s disease. Performed by Rush University, the study specifically zeroed in on the effect of a diet called the Mediterranean-DASH Intervention for Neurodegenerative Delay or MIND.

Researchers studied over 900 middle-aged Americans over the course of five years who were on the MIND diet, which consists of foods like fish, grains, vegetables, and healthy fats. Among the participants who followed the MIND diet “rigorously,” the researchers found the reduced risk of Alzheimer’s to be 53 percent. Those who followed it “moderately well” presented a reduced risk of 35 percent.

Disturbed Sleep Could Increase Risk

During a study performed on mice at the University of California Berkeley’s Sleep and Neuroimaging Lab, researchers found signs that sleep disturbances my increase the risk of Alzheimer’s disease. Sleep, they found, allows the brain to rid itself of a “stringy toxic protein”—one that builds up in the brains of those with Alzheimer’s.

The lead researcher equated this process to the work of a dishwasher, cleaning out the “garbage protein.” In the mice with disturbed sleep, the brain had less time to get rid of the toxin, causing a buildup of trash.

Scientists say this buildup can impair mental functions like learning and forming new memories—leading them to conclude that chronic disturbed sleep may be an “environmental risk factor for Alzheimer’s.”

Coffee May Decrease Risk

Good news for caffeine-loving Americans: Researchers found evidence this year that coffee can help reduce the risk of Alzheimer’s. The study was a part of a larger analysis of mortality by the Harvard School of Public Health.

Analyzing more than 90,000 women and 40,000 men, the researchers found consumption of coffee to have a “significant inverse association” with deaths due to neurological diseases such as Alzheimer’s.

Coffee’s ability to potentially lower risk of death from Alzheimer’s wasn’t the only discovery—researchers found those who drank it regularly to be less likely to die from a handful of other conditions, ranging from suicide to heart disease. The scientists theorized that “bioactive compounds” in coffee may be responsible, but stressed the need for additional research to make a conclusion.

Stress Could Increase Risk

A study this December provided yet another reason to find a way to de-stress this holiday season: an increased level of it may be a risk factor for Alzheimer’s. Published in the Alzheimer Disease and Associated Disorders journal, the study followed 500 adults over the course of three years to measure their stress levels.

Stress level was determined through a series of test performed each year. In the group of individuals who “perceived” themselves to be under the highest level of stress, researchers found an increased risk of early cognitive decline. One potential cause, they suggested, is an increase of cortisol in stressed individuals, which weakens nerve cells in the brain.

Alcohol May Reduce Risk

The most recent study—and likely the most popular—comes from the University of Copenhagen where researchers linked moderate alcohol consumption with a lower risk of death in people with Alzheimer’s. Among the 320 Alzheimer’s patients that were studied, the group that consumed two to three drinks a day were found to have a 77 percent lowered risk of dying.

Scientists were unable to determine why exactly alcoholic beverages—ranging from whiskey to beer—may influence this. They said the research builds on earlier studies suggesting alcohol intake may have a “protective effect” on the brain. Since this runs in direct contradiction to other studies (which show alcohol’s negative effects on the brain), further research is needed.

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The studies, while undoubtedly intriguing, should all be taken with a grain of salt. While the concept that a cup of coffee and three beers a day could significantly reduce your risk of Alzheimer’s risk is appealing, science is far from making a final conclusion. If the amount of studies performed this year is any indication, however, it won’t be long before they do.