Epigenetic Aging and Associated Factors in Japanese People with HIV: A Protocol for a Single-Center Cross-Sectional Study

For decades, the story of HIV was defined by a race against time. Once a fatal diagnosis, the virus has been transformed by modern medicine into a manageable chronic condition. With daily medication, people living with HIV can now expect to live long, healthy lives, often reaching ages similar to the general population. Yet, as this population ages, a new question has emerged: does the virus, or the long-term treatment required to control it, change how the body ages? Scientists are increasingly looking beyond the number of years a person has lived to measure something called biological age. This is a way of gauging how worn out the body's systems actually are, which can differ from a person's birth date. To measure this, researchers examine tiny chemical tags on our DNA, known as methylation. These tags act like a biological clock, ticking away and changing as we get older. When a person's biological clock runs faster than their actual calendar age, it is called epigenetic age acceleration, a sign that the body is aging prematurely and may be at higher risk for age-related diseases like heart trouble or cancer.

A team of researchers in Japan has launched a specific study to understand how this biological aging process plays out in Japanese people living with HIV. While similar studies have been conducted in Western countries, there is very little data on how this phenomenon affects the Japanese population, where genetic backgrounds and lifestyles can differ. The researchers are not waiting for the future to see what happens; they are taking a snapshot of the present to understand the current state of these patients. They have designed a study to look at 100 adult men who have been taking HIV medication for at least a year. By focusing on men who are already stable on their treatment, the team hopes to see if the length of time they have been on medication, the specific types of drugs they take, and their daily habits are linked to how fast their biological clocks are ticking.

The study is taking place at a single medical center in Tokyo, where doctors are carefully selecting participants who fit strict criteria to ensure the results are clear. The researchers are looking for men who have been diagnosed with HIV, are currently receiving outpatient care, and have been on antiretroviral therapy for at least 12 months. To keep the data clean and avoid confusion from other health issues, they are excluding anyone with active cancer, severe autoimmune diseases, or recent major surgeries. They also exclude those with active hepatitis B or C, as these liver infections could independently speed up aging. The goal is to create a group where the only major variable is the history of HIV and its treatment. Once a participant agrees to join, the process involves two visits. During the first visit, the patient signs consent forms and fills out detailed questionnaires about their sleep, diet, exercise, and alcohol consumption. A week later, they return for a second visit where doctors measure their height and weight, check their physical frailty, and draw blood.

From these blood samples, the researchers extract DNA to look at the methylation patterns that serve as the biological clock. They use a high-tech chip that can read nearly one million specific spots on the DNA strand to calculate an epigenetic age. This calculated age is then compared to the person's actual chronological age. If the biological age is higher, it indicates acceleration. The team is using several different methods to calculate this age, including some that were specifically developed using data from Japanese people, ensuring the results are relevant to the local population. They are also measuring a wide range of other factors in the blood, such as immune cell counts, inflammation markers, and metabolic indicators, to see if these physical signs of health or stress correlate with the speed of the biological clock.

The primary question driving this work is whether the duration of HIV treatment is linked to the speed of aging. Previous research in other parts of the world has suggested that while the virus itself can accelerate aging, starting treatment might slow this process down, or even reverse it over time. However, it is not yet clear if this holds true for Japanese men, or if certain types of HIV medications have a stronger effect than others. The researchers are also investigating whether lifestyle factors, such as smoking, diet, and physical activity, play a role. They want to know if a person who exercises regularly and eats a balanced diet shows signs of slower biological aging compared to someone with less healthy habits, even if both are living with HIV.

This study is a cross-sectional look, meaning it captures a single moment in time rather than following the same people over many years. Because of this design, the researchers cannot prove that one thing causes another; they can only identify strong associations. For example, if they find that people who have been on medication longer have slower biological clocks, they cannot say for certain that the medication caused the slowdown, though it is a strong possibility. The study also lacks a control group of people without HIV for direct comparison, so the focus is entirely on understanding the patterns within the HIV-positive population itself. The researchers acknowledge these limits, noting that the findings will serve as a foundation for future studies that can track changes over time and include women and other groups.

The team has set a target of 100 participants to ensure they have enough data to detect meaningful patterns. They are using advanced statistical tools to analyze the connections between the biological clock and the various factors they have measured, from the specific drugs a patient takes to their history of other infections like tuberculosis. If the study finds that certain lifestyle choices or medication regimens are linked to slower biological aging, it could offer new insights into how to manage HIV not just as a viral infection, but as a condition that requires holistic care to protect long-term health. The results will be shared in scientific journals, providing a clearer picture of how HIV and its treatment interact with the aging process in Japan, a crucial step toward ensuring that the long lives of people with HIV are also healthy and vibrant ones.