A new American study has raised a deeply unsettling question for millions of Indian families: when an elderly mother or grandmother says she cannot sleep at night, could her brain already be sending out an early distress signal?

Researchers from the University of California San Diego have found that older women with a stronger genetic risk for Alzheimer’s disease showed more memory problems and greater buildup of a harmful brain protein when they reported poor sleep. The findings, published from the ongoing Women Inflammation Tau Study, are now adding urgency to what many families dismiss as “normal old-age sleep trouble".

The study examined 69 women over 65. Scientists asked detailed questions about sleep quality, carried out memory tests, and used advanced brain scans to track tau— a sticky protein strongly linked with Alzheimer’s disease, the world’s most feared memory disorder.

What shocked researchers was not just the memory decline. It was the type of memory being affected.

Women with poor sleep and a higher genetic risk struggled more with visual memory—the brain’s ability to recognise faces, remember directions, and identify places. In simple terms, the danger may begin not with forgotten names but with confusion over familiar roads, neighbourhoods, or even the faces of loved ones.

Scientists say tau acts almost like “brain garbage". During healthy sleep, the brain performs a natural cleaning process. But when sleep keeps breaking night after night, that waste may start piling up. Over time, the toxic protein forms clumps inside the brain, damaging cells involved in memory and thinking.

The researchers observed that the relationship seems to be reciprocal. Poor sleep may increase tau buildup while further damaging sleep cycles. It becomes a vicious loop — a silent 3 AM attack happening inside the brain.

The warning carries particular importance for women. Nearly two-thirds of Alzheimer’s patients worldwide are women, according to the Alzheimer's Association. Scientists have long observed that women report more insomnia, lighter sleep and repeated nighttime wakeups than men, especially after menopause.

That combination may be more dangerous than previously understood.

Dr Kristine Yaffe, a leading Alzheimer’s researcher at the University of California, San Francisco, has previously described sleep as one of the most important “modifiable risk factors” for brain decline. Separate studies from Harvard Medical School and the National Institutes of Health have also linked chronic sleep disruption with abnormal brain protein accumulation and faster cognitive ageing.

Inside laboratories in California, researchers tracked tau deposits using specialised PET brain scans—expensive imaging tools usually only available in advanced centers. Yet the striking part of this new research is surprisingly simple: the first warning sign may come from nothing more than a sleep complaint.

That makes the findings especially relevant in countries like India, where dementia cases are rising rapidly but often go unnoticed until severe symptoms appear.

Experts say families frequently ignore sleep complaints in older women. A grandmother staying awake until 3 AM is often treated as a harmless part of ageing. But scientists now believe those restless nights could represent one of the earliest visible clues of future brain disease, especially in women already carrying higher genetic vulnerability.

Importantly, researchers stressed there is still hope.

Researchers believe that improving sleep habits, unlike genes, is possible. Better sleep hygiene, treatment of insomnia, stress management, reduced late-night screen exposure, and medical evaluation of persistent sleep problems may help protect long-term brain health. Scientists say inexpensive sleep questionnaires could even become early screening tools in future Alzheimer’s prevention programmes.

For families, the message is blunt and urgent: if an elderly woman repeatedly complains of broken sleep, it may be dangerous to dismiss it as “just age".

Tomorrow’s forgotten faces may begin with tonight’s sleepless pillow.