Little Tiger's grandma has always been a sturdy woman, carrying that particular toughness unique to women of her generation.
When she was pushing me to get married and have kids, she never worried about it β she figured helping me raise a child would be easy.
But in the years after childbirth, my own health declined too β my immunity dropped, my muscle strength and mental state deteriorated one by one, and I felt this indescribable weakness.
And then I looked at my mom. She had aged so much. Not the gradual, slow aging β but the kind where one day you look at her and realize she's no longer the person you remember. She walked slower, her back was bent, she started complaining about not sleeping well, about sore legs, about this or that discomfort. She never used to mention these things.
It wasn't until recently, when I came across a study, that I seriously asked myself: beyond the physical labor, what had she quietly been losing over these years?
In 2024, the Proceedings of the National Academy of Sciences published a large study tracking nearly 90,000 middle-aged and older adults. They recorded 7 consecutive days of light exposure data and followed up over 8 years. The conclusion: the brighter the nighttime light exposure, the higher the all-cause mortality risk; the less daytime light exposure, the higher the mortality risk too.
The 10% of people with the brightest nighttime sleep environments had a 21% to 34% higher all-cause mortality risk than the half with the darkest environments, and a 33% to 46% higher risk of death from heart and metabolic diseases.
In 2025, the same team followed up, specifically focusing on cardiovascular health over nearly 10 years. Compared to people with the darkest sleep environments, the brightest nighttime group had: 45% to 56% higher risk of heart failure and myocardial infarction, 23% to 32% higher coronary heart disease risk, 28% to 32% higher atrial fibrillation risk, and 28% to 30% higher stroke risk.
During those years, the one who was awake most often at night wasn't me β it was her. She was the one who woke at the slightest whimper from the baby. Sleep, wake, sleep, wake. Three or four times a night, over three hundred nights a year.
Why does nighttime light harm the heart? There's a type of cell in the eyes that senses ambient light and sends signals to the brain's master circadian clock. When light comes in at night, the brain receives a false signal. Melatonin secretion is suppressed, blood pressure won't drop, heart rate won't slow. Day after day, these disruptions accumulate into cumulative cardiovascular damage.
The study noted that between 2:30 and 3:00 AM is the highest-risk window. That was precisely when my mom was getting up several times each night.
Keeping the curtains drawn during the day was also a problem. During that period, we often kept the curtains drawn. But with insufficient daytime light, the brain couldn't align with external time. The same study showed that people with the least daytime light exposure also had higher mortality risk.
Experts recommend a sleep environment brightness below 1 lux. Swap in blackout curtains, or wear a sleep mask. Cover indicator lights with opaque tape. For daytime, don't keep the curtains tightly drawn. Go outside if you can.
My mom gave more during those years than I'll ever know. My body broke down, and so did hers. The body always keeps score.