How many candles

The Statistics Bureau of Japan will begin asking for chronological age

This year, citizens of the Japan census will be asked for two ages: the traditional chronological age that measures how many trips you have done across the sun – and your biological age – a measure of chemical changes to DNA.

The practice of estimating biological age has been common in doctors offices across Japan for over a decade now, with medical staff pointing to two benefits.

First, it is a better predictor of risk of disease, and thus a better method by which to suggest screening. Indeed, when simply using a biological calculation to vs chronological calculation to pick which candidates to screen, breast cancer detection has increased 15% with limited cost increases, pointing to more efficient screening.

Second, doctors use it as an easy way of describing how lifestyle, exercise and eating habits can improve well being.

“When you show that someone is 50, but their body is acting more like 55 or 60, that’s a wake up call,” says Dr. Sadie Marks, a physician based outside Tokyo.

How is biological age calculated? There is no globally aligned definition, but Japan uses a method known as DNA methylation. Various tests can look at changes in DNA methylation patterns over time, which are then used to estimate an individual's biological age. Scientists generally agree that this method is more accurate than better known biological age alternatives, typically a formula of changes to common biomarkers, such as blood pressure, cholesterol levels, body mass index (BMI), fasting glucose levels, and other markers of inflammation.

Policy makers hope that by collecting and standardizing biological age, policy makers can help better plan for the long term health of the nation, as well as provide better benchmarks to medical researchers.

The Office of the Director General of Policy Planning of Japan also points out on its website no changes have been made to other disclosures. It is still forbidden to discriminate by biological or chronological age in the job market or elsewhere, and no age limit (including retirement) have changed. “The data will help,” says Dr Marks. “I appreciate we have all celebrated the same way of measuring time for centuries. But sometimes new technologies come about and we should use them to live better lives” .