What Is Blue Light? How Does It Impact Sleep?

Updated Dec 14, 2024 | 10:45 PM IST

SummaryScreens of electronic devices such as smartphones, computers, tablets, and televisions emit blue light. But does it impact your natural sleep cycle and circadian rhythm?
Blue Light

Blue Light (Credit: Canva)

Blue light emitted by devices like smartphones, computers, and televisions is becoming a major factor disrupting our sleep cycles. Research reveals that a significant number of Americans use electronic devices close to bedtime, contributing to poor sleep quality. Reducing exposure to blue light, particularly in the evening, is a simple yet effective way to help your body prepare for restful sleep.

What Is Blue Light?

Blue light is part of the visible light spectrum and is emitted by natural and artificial sources like the sun, fluorescent lights, LED lights, and digital screens. This wavelength is known for influencing our alertness, mood, and sleep patterns. During the day, blue light plays a role in regulating circadian rhythms, helping us stay alert and focused. However, exposure to it in the evening can have a detrimental effect on sleep quality.

How Does Blue Light Impact Circadian Rhythms?

Circadian rhythms are 24-hour cycles that control essential bodily functions, including sleep. Light is the primary factor that aligns these rhythms with day and night. Historically, exposure to sunlight during the day helped set our body clocks, signaling when to be awake and when to sleep. However, the widespread use of artificial lighting and electronic devices has introduced more light exposure after dark, disrupting these natural cycles.

Blue light, in particular, has the strongest impact on circadian rhythms. During daylight hours, blue light helps us feel alert by stimulating the brain, raising body temperature, and increasing heart rate. But in the evening, exposure to blue light can confuse the body’s internal clock, suppressing melatonin—the hormone responsible for making us feel sleepy. As a result, our brains may remain in “daytime mode,” preventing us from winding down for the night.

Health Consequences Of Disrupted Sleep

Persistent disruption of circadian rhythms can lead to a range of health issues, including metabolic disorders, poor mental health, and increased risk for conditions like depression and anxiety. Furthermore, the inability to sleep well at night affects cognitive performance, mood, and overall well-being. Chronic exposure to blue light in the evening may significantly contribute to these negative health outcomes.

Devices That Emit Blue Light

Many common devices in our daily lives emit blue light, including:

- Smartphones and tablets

- Computer monitors and laptops

- Televisions and e-readers

- LED and fluorescent lighting

- Video game consoles

How To Minimize Blue Light Exposure

To reduce the effects of blue light on your sleep, here are some practical strategies:

1. Turn off screens before bed: Try to avoid using electronic devices at least two to three hours before bedtime. Reducing screen time helps prevent blue light from interfering with melatonin production.

2. Adjust your lighting: Dim your home’s lights or switch to warmer-toned lighting in the evening. You can also use lamps with red or orange light, which are less likely to impact your circadian rhythms.

3. Night mode settings: Many smartphones and computers have a "night mode" feature that reduces blue light emission. Make use of these features to limit exposure in the hours leading up to bedtime.

4. Blue light-blocking glasses: Special glasses designed to filter out blue light may be helpful for some individuals. These glasses can block or reduce the melatonin-suppressing effects of blue light.

5. Apps for blue light reduction: There are several smartphone and computer apps available that reduce blue light emission, allowing you to use your devices before bed without disturbing your sleep.

6. Create a sleep-friendly environment: If you can’t control light sources in your bedroom, consider using an eye mask to block out ambient light and promote better sleep.

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Healthy BMI But Belly Fat? Why Your Waist May Predict Heart Risk Better

Updated Aug 17, 2026 | 08:13 PM IST

SummaryDespite evidence linking central adiposity to adverse cardiovascular outcomes, BMI remains the most commonly used measure to determine overweight and obesity and assess future cardiovascular risk.
Healthy BMI But Belly Fat? Why Your Waist May Predict Heart Risk Better

Credit: iStock

If you believe having a healthy body mass index (BMI) means you have a low risk of heart disease, you may be wrong. A new study suggests that abdominal fat may predict cardiovascular disease risk better than BMI alone.

The study, published in the Journal of the American College of Cardiology (JACC), found that failing to account for waist circumference (WC) or waist-to-hip ratio (WHR) may lead to misclassification of cardiovascular disease risk.

“Indeed, it appears that WC and WHR reclassify risk defined by traditional BMI thresholds,” said Michael J. Blaha, director of clinical research at the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease.

“We saw individuals with clinically determined normal weight who had elevated central adiposity and high WHR, associating them with higher risk across most outcomes,” Blaha added.

Why BMI Alone May Not Predict Heart Risk

BMI is calculated by dividing weight in kilograms by height in meters squared and is commonly used to diagnose overweight and obesity. However, BMI does not show where body fat is distributed.

  • Visceral fat surrounds the internal organs in the abdominal area and is associated with chronic conditions such as heart disease and diabetes.
  • Subcutaneous fat is located directly under the skin and is not as strongly associated with these conditions.
Central adiposity refers to the accumulation of both visceral and subcutaneous fat around the abdomen. Despite evidence linking central adiposity to adverse cardiovascular outcomes, BMI remains the most commonly used measure to determine overweight and obesity and assess future cardiovascular risk.

What Did the Study Find?

The study examined whether adding WC and WHR to BMI could better predict future cardiovascular risk. Researchers looked at more than 260,000 people over an average of 20 years. They found that central adiposity could identify cardiovascular risk that BMI alone may miss.

Among people classified as having normal weight by BMI:

  • 5% had high waist circumference
  • 18% had high waist-to-hip ratio
Among people with overweight:

  • 39% had high waist circumference
  • 40% had high waist-to-hip ratio
Among people with obesity:

  • 9% had low waist circumference
  • 45% had low waist-to-hip ratio

People with normal weight or overweight who had clinically defined high WC or WHR had a 15%–50% greater risk for most heart problems.

People with obesity and low WC did not have a significantly different risk of outcomes compared with those who had normal weight and low WC, except for all-cause mortality, for which their risk was significantly lower.

“Our findings emphasize the critical role of identifying elevated central adiposity, even in individuals with a normal BMI or with a BMI in the overweight range. Relying solely on BMI may result in misclassification of cardiovascular risk across a wide range of cardiovascular outcomes,” said Zeina A. Dardari, lead author of the study.

“We encourage clinicians to consider central adiposity distribution across the entire BMI spectrum when evaluating cardiovascular risk in primary prevention settings,” she added.

What Were the Study's Limitations?

The researchers did not have information on several factors that can influence cardiovascular disease risk, including:

  • Physical activity
  • Diet
  • Genetic risk for obesity

The study also included only one assessment of waist circumference and waist-to-hip ratio. This limited the researchers' ability to understand how changes in abdominal fat accumulation over time may influence cardiovascular disease risk.

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Organ Donation: The Gift Of Life

Updated Aug 17, 2026 | 05:35 PM IST

SummaryOrgan donation can save or significantly improve multiple lives by providing vital organs to people with end-stage organ failure, making awareness, registration, and informed consent essential.

Credit: AI

Organ donation is one of the most profound ways in which we can give the gift of life to another person. To raise awareness about organ donation, it is important address common myths and encourage more people to consider pledging their organs.

India has a large number of patients waiting for organ transplants, including transplants of the liver, kidney, heart, pancreas, intestine and other organs and tissues.

Despite the significant need, organ donation rates remain low, with lack of awareness and several misconceptions continuing to be major barriers. One organ donor can potentially save multiple lives. However, for this to happen, it is important that people understand the process and make an informed decision about organ donation during their lifetime.

Busting Common Myths About Organ Donation

1. “My religion does not permit me to donate my organs.”

2. “Organs can only be donated after the heart stops beating.”

For most organs, donation after brain death is possible when the brain has permanently stopped functioning, but the heart is still beating, which generally occurs in an intensive care setting. Corneas can also be donated after death within a limited time period. This is why pledging your organs during your lifetime and discussing your decision with your family is important.

3. “Organ donation will disfigure or mutilate the body.”

Organ retrieval is performed by trained medical specialists in an operating theatre. The surgical incision is carefully closed after the procedure, and the body is not mutilated.

Also read: Post-Organ Donation And Transplant Care: How Can Donors And Recipients Stay Healthy?

4. “I can buy a kidney or liver for my family member.”

5. “If I donate a kidney, I will become weak or handicapped.”

A healthy person who is found suitable for living kidney donation through the required medical evaluation can generally continue their normal life after donation. The remaining kidney is capable of maintaining normal kidney function.

6. “A kidney donor has to take lifelong medicines.”

Kidney donation does not mean that a healthy donor has to take lifelong medication simply because they have donated a kidney. Some pain medication may be required during the initial recovery period, while the remaining healthy kidney continues to perform its function.

7. “I will have severe dietary restrictions after donating a kidney.”

According to the source material, kidney donors do not generally need specific dietary restrictions solely because they have donated a kidney, as the remaining kidney continues to maintain normal kidney function.

8. “I will not be able to have children after donating a kidney.”

Both men and women who donate a kidney can have children. For women, the source recommends waiting one year after donation before becoming pregnant to allow the body to recover completely.

9. “I am over 60, so I am too old to donate.”

Age alone does not determine whether someone can donate. The health of the donor and the condition of the organs are important considerations, and suitability is determined through medical evaluation.

Also read: World Organ Donation Day 2026: Too Old Or Too Sick To Donate Organs? Doctors Bust Key Myths

What Can We Do To Encourage Organ Donation?

• Consider pledging your organs during your lifetime and communicate your decision clearly to your family.

• Talk to your family, friends and colleagues about organ donation and help dispel common myths.

• Encourage community organisations to participate in creating awareness around organ donation.

• Do not assume that you are medically unfit to donate. A team of medical experts evaluates the donor and determines suitability.

• Organ donation is a completely voluntary decision. No individual should be pressured into donating an organ.

• Patients waiting for an organ transplant should approach a licensed transplant hospital and complete the necessary registration formalities, including through the NOTTO system.

Organ donation is ultimately about giving someone another chance at life. We should not take our organs with us; they can be used to save lives and give hope to those waiting for a transplant.

By Dr Sanjeev Gulati, Chairman, Nephrology, Fortis, Vasant Kunj

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Maternal Anemia: Why It’s A Major Pregnancy Risk For Indian Women And How to Prevent It

Updated Aug 16, 2026 | 09:37 AM IST

SummaryMaternal anemia is a major pregnancy concern in India, potentially affecting mothers and babies. Early screening, iron-rich nutrition, supplements, and timely treatment can reduce complications.
Maternal Anemia: Why It’s A Major Pregnancy Risk For Indian Women And How to Prevent It

Credit: iStock

Anemia remains one of the least talked about threats to a safe pregnancy in India. The National Family Health Survey-5 data shows that 52.2% of pregnant women in India were anemic. This translates to at least one in two expectant mothers entering pregnancy with insufficient hemoglobin to meet her own and her baby’s needs.

Pregnant women with iron-deficiency anemia may feel unusually tired, weak or short of breath. Some women may suffer from dizziness, headaches, palpitations or reduced ability to concentrate. However, symptoms can be subtle and this is why routine antenatal screening is important even if the woman feels well.

Left unaddressed, it raises the risk of preterm birth, low birth weight, postpartum haemorrhage, and maternal fatigue severe enough to affect daily functioning and recovery after delivery.

Severe anaemia can also reduce a woman's ability to tolerate blood loss during delivery, making even an otherwise uncomplicated birth potentially more challenging.

Why pregnancy makes it worse? Well, blood volume expands by nearly 50% during pregnancy, and the growing fetus draws heavily on maternal iron stores, especially in the second and third trimesters. Most Indian women begin pregnancy with iron stores already depleted by poor dietary intake, frequent pregnancies, or heavy menstrual blood loss. So, the added demand tips many into overt anaemia.

Do's:

1. Start Antenatal Care early. You should get a baseline haemoglobin test at your first antenatal visit, and repeat this each trimester or more if needed.

2. Iron and folic acid tablets must be taken in accordance with the prescription given. It is best to start with them before conceiving or as soon as possible in the pregnancy process, preferably in discussion. The dietary consumption may not always be sufficient to cater to the increased demands during pregnancy.

3. Pair iron-rich foods with vitamin C. A squeeze of lemon with dal or leafy greens meaningfully improves absorption. Indian gooseberry (amla), guava, oranges and tomatoes improve absorption of non-heme iron from plant based foods.

4. Include iron-dense foods regularly like leafy greens, jaggery, dates, legumes, eggs. If non-vegetarian, eat lean meat or fish, meat or poultry.

5. Treat underlying causes. Get heavy periods, worm infestations or unexplained fatigue evaluated before conception if possible.

6. Ask about your ferritin level, not just haemoglobin, since ferritin reveals depleted iron stores earlier.

Anaemia is not always caused by iron deficiency. B12 or folic acid deficiency, problems with haemoglobin production, infections, and many other medical conditions can also be contributing factors.

Also read: 'My Periods Are Painful' Is Not Always Normal: When Could It Be A Sign of Endometriosis?

Don'ts:

1. Do not stop iron supplements simply because you feel better. Treatment usually needs to continue for the recommended period to replenish iron stores.

2. Don't take iron tablets with tea, coffee or milk. These block absorption. Space them at least an hour apart.

3. Do not skip supplements because of nausea or constipation. Ask your doctor for alternate formulations instead of foregoing the supplements.

4. Don't assume fatigue is ‘normal pregnancy tiredness’ without a haemoglobin check. Persistent breathlessness, dizziness or a racing heart need evaluation.

5. Don't self-medicate with over-the-counter iron doses. Both too little and too much iron can cause harm.

6. Don't ignore mild anaemia on the assumption that it will ‘sort itself out’. It typically worsens as pregnancy progresses and has to be actively treated.

Anemia in women is mostly preventable and treatable early. Regular antenatal check ups, proper supplementation, balanced diet and timely treatment can go a long way in reducing its impact on the mother and baby. The key message is simple, really. Screen early, do not wait for symptoms, treat appropriately and maintain adequate iron stores throughout pregnancy.

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