Wondering when to stop drinking coffee and using screens to avoid messing with your sleep? How frequently you should wash your sheets?

Scientists have been looking for answers to these questions too.

You can use their answers to guide many of the decisions you make on a nightly basis, from what you drink at night to how often you do laundry.

1. Watch your mid-afternoon caffeine intake.

The Mayo Clinic advises adults to limit their caffeine intake to 400 mg per day, or the equivalent of about two to three coffees.

Caffeine content can differ dramatically based on the type of coffee, however. Just 1.5 cups of Starbucks contains 400 mg of caffeine, while you'd need four cups of McDonald's drip coffee to equal that amount.

Like too much of anything, excess caffeine comes with risks, including migraine headaches, irritability, upset stomach, and even muscle tremors – so it's important to know how much you're getting.

2. On your commute home, don't agonise over germs.

A team of geneticists made headlines in 2015 for a mission to document all the bacteria on the New York City subway. They turned up nearly 600 different species of microbes crawling around on all those greasy rails.

Before whipping out the hand sanitiser and tissues, keep this in mind: Almost all of the germs they found were completely harmless.

In fact, there's evidence to suggest that regular exposure to germs helps keep our immune systems healthy by priming it to more easily recognise dangerous microbes in the future.

The idea could partially explain why children who grow up around animals and in rural areas are less likely to develop conditions like asthma than children who don't.

3. Skip happy hour, or go simply for the food and company.

Alcohol is one of the world's most widely consumed drugs, but drinking even small amounts – as little as one glass of wine or beer a day – has been linked with a host of negative side effects, including cancer.

In November, the American Society of Clinical Oncology, a group of the nation's top cancer doctors, released an unprecedented warning in which it told Americans to drink less.

"ASCO believes that a proactive stance by the Society to minimise excessive exposure to alcohol has important implications for cancer prevention," the statement said.

So at your next happy-hour event, consider skipping the booze or doing something else.

4. Stay hydrated.

Staying hydrated is vital. Our bodies are 60 percent water, and not getting enough can lead to headaches, fatigue, and even overeating. Still, contrary to popular opinion, you don't necessarily need to drink eight glasses of water a day.

Instead, your daily hydration requirement can change based on several factors, from how much you worked out that day to the weather outside.

Certain foods are also a good water source, so eating more of them may mean you need to drink less. Cauliflower, eggplant, peppers, and spinach are all 92 percent water. Carrots, green peas, and even white potatoes are more than 79 percent.

5. Take breaks from screens to avoid eye strain.

Many of us go from starting at computers to staring at our phones, and as a result our eyes are often dry, itchy, blurry, or irritated. Ophthalmologists call this condition "digital eyestrain."

To avoid it, make sure you're drinking (and blinking) enough and avoid reading your phone under the glare of a lamp. You can also practice what's known as the 20-20-20 rule.

Every 20 minutes, look at something at least 20 feet away for 20 seconds. This will allow your eyes to rest, Rahul Khurana, the clinical spokesman for the American Academy of Ophthalmologists told my colleague Kevin Loria.

6. If you go out for dinner, plan on taking up to a third of it home.

The baseline portion sizes of our snacks and meals have ballooned over the past 40 years – even the plates and cups we serve them on have gotten noticeably bigger.

The average size of many of our foods – whether fast food, sit-down meals, or even items from the grocery store – has grown by as much as 138 percent since the 1970s, according to data from the American Journal of Public Health, the Journal of Nutrition, and the Journal of the American Medical Association.

So be mindful of portion sizes, and if you're eating out, consider taking anywhere from a third to half of it to go.

7. Put away screens for at least 30 minutes before bedtime.

The blue light that illuminates our screens also tamps down on the production of melatonin, a key hormone our brains use to tell our bodies to start preparing for sleep.

That's something you don't want to be doing at night, especially right when you're heading to bed. Experts recommend at least 30 minutes of no-screen time before bedtime.

8. Before you tuck in for the night, make sure your sheets are clean.

Our beds can blossom into a "botanical park" of bacteria and fungus in as little as a week, New York University microbiologist Philip Tierno told Business Insider.

The combination of sweat, animal dander, pollen, soil, lint, dust-mite debris, and plenty of other things is enough to make anyone sick, let alone someone with allergies. So clean your sheets at least once every seven days.

This article was originally published by Business Insider.