What can my blinking tell me about my health?

Dr. Trisha Pasricha. PHOTO: health.harvard.edu

Q: I feel like I’m blinking more often than usual. What can blinking tell me about my health? And why do we blink?

A: We blink about once every three to five seconds and usually don’t even realize it’s happening, despite losing an incredible amount of our daily visual input to blinking – up to 10 percent.

Blinking serves several practical purposes: It wets and cleans the surface of the cornea and can reflexively protect the eye from rapidly approaching objects. But that’s not quite the end of the story.

In some cases, a change in blinking might herald a health problem. Here are some reasons blinking may change that can tell you something about your health:

Slow or infrequent blinking: Decreased blinking can be one of the early signs of Parkinson’s disease. One important neurotransmitter influencing our ability to pay attention and show flexibility is dopamine. Several studies have found that the rate at which we spontaneously blink mirrors the neurotransmitter’s activity in our brains – the lower the dopamine, the more we fixate on one subject, and the less frequently we blink. And the hallmark of Parkinson’s is the loss of dopamine-producing nerve cells.

Patients with the autoimmune condition Graves’ disease also experience changes to their blinking pattern, which may be related to cornea damage. And other neurological conditions besides Parkinson’s, such as stroke, can slow the normal blinking rate. Slower blinking has also been associated with head injury among athletes.

Excessive blinking: Increased blinking can be a sign of sleepiness while trying to perform a demanding task such as driving while drowsy (if you notice this happening, keep everyone on the road safe and get some rest before continuing your journey). People who are suffering from pain or experiencing very bright lights also blink more frequently.

Excessive blinking can occur when your body tries to compensate for dry eye disease, which occurs for a number of reasons, including Sjogren’s syndrome or side effects from certain medications like antihistamines.

Dry eye disease is also incredibly common among frequent screen-users. We blink less frequently when we stare at our screens.

If you plan on spending hours in front of your computer, set 20-minute timers to step away for a minute or two from your screen. I also like the concept of “blind working” – closing your eyes for brief, deliberate breaks in your workday when you actually don’t need to have them open, such as during a telephone call or while waiting for a program to load. Heightened screen time may also be associated with damage to the glands that keep our eyes healthy as well as myopia.

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Why do we blink?

In many situations, people blink in unexpected patterns that don’t seem to have anything to do with maintaining their eyes’ moisture.

In the 1920s, scientists studying this phenomenon wondered: If blinking was not simply there to dust off the corneas, what did it really mean?

Some of their observations made intuitive sense – they noted that people blink more frequently while smoking; smoke is a known corneal irritant. But they also found people blinked less frequently while reading than they did while talking, when the environment was otherwise the same – and oddly, that people reading almost always blinked at punctuation marks instead of text.

Other findings were just as puzzling. Unexpected sounds, even if not loud, caused children to blink. And people blinked more frequently when they became angry or anxious.

Decades of research has revealed that blinking is much more than the windshield wiper of the body but rather a window into the state of our minds – how carefully our attention is focused and whether we’re ready for new stimuli.

Studies have shown that increased spontaneous blinking can be a sign of gathering new information – especially when it challenges the “rules” of a known environment. For instance, babies in bilingual households blink more rapidly as they switch between hearing different languages spoken, which correlates to signaling in areas of the brain governed by dopamine. And people blink in synchrony when watching the same movie – researchers have found that we tend to stare continuously while the action of the main character unfolds, but we all start to blink unconsciously during the same implicit narrative breaks – such as when there’s a shot with no humans in the scene.

In a similar way, blinking plays a role in our social communication. Scientists have measured that when two people are communicating smoothly with each other and holding the other’s interest, their blinking patterns start to align.

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How did humans evolve to blink?

Scientists believe blinking developed several times across evolutionary history – and in some cases, like with snakes, became lost again. A study of mudskippers published last year in the Proceedings of the National Academy of Sciences hypothesized that it was the transition from aquatic life to land that made blinking beneficial to survival – even for our own ancestors, who also emerged from the sea several hundred million years ago.

One reason blinking on land is critical is because the corneas of our eyes don’t have blood vessels and so they derive oxygen by diffusion from the environment surrounding them. Oxygen diffuses more easily across wet surfaces, and spontaneous blinking helps maintain a thin, fluid film layer on our eyes. Another reason is that dangerous objects travel much more quickly through thin air than they would through water – so blinking reflexively to shield the eyes from injury is significantly more important on land.

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What I want my patients to knowPeople often buy laptop raisers or elevate their screens to eye level. Instead, try placing the screen at a 10-degree downward gaze angle (and ideally two to three feet away from you). Doing so may relax the muscles around your eye to help you blink more completely, and it can reduce tear evaporation. What can my blinking tell me about my health?
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Why does a leap year have 366 days?


You may be used to hearing that it takes the Earth 365 days to make a full lap, but that journey actually lasts about 365 and a quarter days. Leap years help to keep the 12-month calendar matched up with Earth’s movement around the Sun.

After four years, those leftover hours add up to a whole day. In a leap year, we add this extra day to the month of February, making it 29 days long instead of the usual 28.

The idea of an annual catch-up dates back to ancient Rome, where people had a calendar with 355 days instead of 365 because it was based on cycles and phases of the Moon. They noticed that their calendar was getting out of sync with the seasons, so they began adding an extra month, which they called Mercedonius, every two years to catch up with the missing days.

In the year 45 B.C.E., Roman emperor Julius Caesar introduced a solar calendar, based on one developed in Egypt. Every four years, February received an extra day to keep the calendar in line with the Earth’s journey around the Sun. In honor of Caesar, this system is still known as the Julian calendar.

But that wasn’t the last tweak. As time went on, people realized that the Earth’s journey wasn’t exactly 365.25 days – it actually took 365.24219 days, which is about 11 minutes less. So adding a whole day every four years was actually a little more correction than was needed.

In 1582, Pope Gregory XIII signed an order that made a small adjustment. There would still be a leap year every four years, except in “century” years – years divisible by 100, like 1700 or 2100 – unless they were also divisible by 400. It might sound a bit like a puzzle, but this adjustment made the calendar even more accurate – and from that point on, it was known as the Gregorian calendar.

What if we didn’t have leap years?

If the calendar didn’t make that small correction every four years, it would gradually fall out of alignment with the seasons. Over centuries, this could lead to the solstices and equinoxes occurring at different times than expected. Winter weather might develop in what the calendar showed as summer, and farmers could become confused about when to plant their seeds.

Without leap years, our calendar would gradually become disconnected from the seasons.

Other calendars around the world have their own ways of keeping time. The Jewish calendar, which is regulated by both the Moon and the Sun, is like a big puzzle with a 19-year cycle. Every now and then, it adds a leap month to make sure that special celebrations happen at just the right time.

The Islamic calendar is even more unusual. It follows the phases of the Moon and doesn’t add extra days. Since a lunar year is only about 355 days long, key dates on the Islamic calendar move 10 to 11 days earlier each year on the solar calendar.

For example, Ramadan, the Islamic month of fasting, falls in the ninth month of the Islamic calendar. In 2024, it will run from March 11 to April 9; in 2025, it will occur from March 1-29; and in 2026, it will be celebrated from Feb. 18 to March 19.

Learning from the planets

Astronomy originated as a way to make sense of our daily lives, linking the events around us to celestial phenomena. The concept of leap years exemplifies how, from early ages, humans found order in conditions that seemed chaotic.

Simple, unsophisticated but effective tools, born from creative ideas of ancient astronomers and visionaries, provided the first glimpses into understanding the nature that envelops us. Some ancient methods, such as astrometry and lists of astronomical objects, persist even today, revealing the timeless essence of our quest to understand nature.

Ancient Egyptians were dedicated astronomers. This section from the ceiling of the tomb of Senenmut, a high court official in Egypt, was drawn sometime circa 1479–1458 B.C.E. It shows constellations, protective gods and 24 segmented wheels for the hours of the day and the months of the year. NebMaatRa/Wikimedia, CC BY

People who do research in physics and astronomy, the field that I study, are inherently curious about the workings of the universe and our origins. This work is exciting, and also extremely humbling; it constantly shows that in the grand scheme, our lives occupy a mere second in the vast expanse of space and time – even in leap years when we add that extra day.


Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.The Conversation

Bhagya Subrayan, PhD Student in Physics and Astronomy, Purdue University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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