First, the good news: over the last century, our lives have gotten significantly longer.

Thanks to medical intervention and scientific research, the average life expectancy in the US has leapt from age 47 in 1900, to nearly 79 over a century later. Now for the bad news, according to a recent CDC report, our lives are getting incrementally shorter—with the most recent data averaging our lifespan at around 78.6 years, down from 78.9 over the past two years.

Of course, that's not the case in Japan, the country with the highest life expectancy—84.2—and home to the world's oldest living person, Kane Tanaka. 115 years old and counting, Tanaka credits her longevity to her family and getting plenty of sleep.

Research backs up Tanaka's claims. Family has a direct link to longevity, with genetic factors playing a strong role in life expectancy—by predisposing individuals to certain diseases as well as the increased ability to fight certain diseases. But data from the Harvard Study of Adult Development also suggests that meaningful relationships with family or friends may boost overall physical health.

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In the study spanning 80 years, with 1,300 participants, researchers found that those with stable, supportive relationships lived both happier and longer lives.

"When we gathered together everything we knew about them about at age 50, it wasn't their middle-age cholesterol levels that predicted how they were going to grow old," noted the study's lead researcher, Robert Waldinger, a professor of psychiatry at Harvard, during a TED Talk he gave on his findings. "It was how satisfied they were in their relationships. The people who were the most satisfied in their relationships at age 50 were the healthiest at age 80."

Multiple studies have shown sleep is another key factor in living longer. According to one by the American Cancer Society, individuals who slept at least 7 hours a night were more likely to live longer. Lack of sleep has been linked to everything from heart disease to diabetes, as the body—specifically the brain—requires enough down time to replenish the healthy balance of everything from hormones, proteins, and enzymes to memory function.

"Sleep is not just a passive state but a fairly active state on the molecular level," Dr. Allan Pack, director of the Center for Sleep and Circadian Neurobiology at the University of Pennsylvania, told Time in 2017. "During the day, the brain is using energy resources to fire neurons. At night, a switch turns on so the sleeping brain can take advantage of the metabolic downtime to do some cleaning up."

If the idea of a 7-hour-a-night rest seems absurd given the realities of child-rearing, careers, and nonstop social media, there's still hope for you. A recent study by the Stress Research Institute at Stockholm University suggests that you can make up for lost sleep, and essentially bank the hours you've lost on weekends.

Still, a long life requires a lot more than just hitting the snooze button. The latest study by Harvard's T.H. Chan School of Public Health analyzed a pool of over 100,000 people for over three decades to determine what exactly impacts our overall health. According to their findings, it all comes down to five key factors—none of which are surprising.

1. Not smoking. The CDC states that smokers live on average 10 years less than non-smokers. Abstaining from cigarettes is crucial to a longer, healthier life.

2. A healthy BMI: Forget that number on your old-school scale. A better measure is your Body Mass Index, which may help to predict if your predisposed to conditions like diabetes or heart disease. (You can calculate your BMI and find your optimal numbers here.)

3. Daily exercise: Researchers suggest daily regimen of 30 minutes of moderate to intense physical activity. So if you're going for a walk, make it brisk or pick up the pace to a jog while you listen to whatever podcast is cued up on your phone.

4. Moderate alcohol consumption: While recent studies have touted the health benefits of red wine, Harvard's researchers found that moderation is key when it comes to drinking. That means no more than one drink a day for women and up to two drinks a day for men. (Hey, they didn't say NO drinking.)

5. A balanced diet. Researchers found that participants who consumed a diet of veggies, fruits, whole grains, polyunsaturated fatty acids, and long-chain omega-3 fatty acids (fish, legumes, nuts and seeds) had a lower risk of mortality than those who regularly ate red meat, sugar, and processed foods.

If checking off all these boxes seems like a bit of a challenge, here's another way to increase your lifespan: move to Sardinia. For years, longevity experts have been captivated by residents of a small Italian island off the Mediterranean that boasts the oldest living residents in the world. It's believed that their mostly plant-based diets, physically active lifestyles (shepherding, walking everywhere), tight-knit family ties, and respect for the vast elderly community—have all contributed to an abundance of centurions in the region. In particular, the social aspects of Sardinian life—which emphasizes human (non virtual) interaction and shared leisure time.

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"From a psychological perspective, the social context is fundamental to get old well," Maria Chiara Fastame, a psychologist based at the University of Cagliari, told CNN.

To wit, scientists have recently been zeroing in on happiness as key to a long life. Community, work-life balance, and financial stability all play a role in overall happiness—which is linked to lower stress levels and healthier physical functioning.

Another secret to happy living? Lowering the expectations we put on ourselves.

"The most important advice we offer people about longevity is, 'Throw away your lists,'" Howard Friedman, co-author of TheLongevityProject, toldTime in February. "We live in a self-help society full of lists: 'lose weight, hit the gym.' So why aren't we all healthy?"

Maybe it's because some of us are missing out on one surprising longevity secret: dog ownership.

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Researchers at the University of Sweden examined the link between longer life-spans and dog ownership and their findings were remarkable. The study of over 3 million people, published in Scientific Reports in 2017, found that dog owners had a lower risk of heart disease and other fatal health issues than non-dog-owners. This was particularly true in a comparison of people who lived alone. Single people with a dog to care for were 33% less likely to die prematurely than singles who were dog-free.

In terms of physical activity, walking the dog a few times a day adds up. Plus, dog owners are exposed to more allergens which can foster a more resistant immune system. And let's not discount the psychological benefits of pet ownership—which has been linked to a decrease in stress and loneliness, both of which can take a toll on your overall health.

"For those of us who have dogs, like me, the possibility that a dog might help psychological health seems very credible," Dr. Thomas Lee of Harvard Medical School, stated in the university's health publication. "With our dog at home, my wife and I don't feel as alone."

While so many factors play into longevity and there's no quick fix for a longer life, sometimes a cuddle from a four-legged friend is just what the doctor ordered.