Scientists Found a New Reason You're Getting Old

Land emphasizes that light is the number one regulator of circadian rhythms. The morning light pulse increases cortisol, which is naturally high in the morning. Without this signal, the circadian rhythm drifts. He notes that older individuals have a diminished cortisol response, so they may need additional strategies like caffeine. He also mentions that the unique wavelengths from the sun (e.g., UV, infrared) are not fully replicated by artificial lamps, but lamps are an acceptable substitute when sunlight isn't available.

Land hypothesizes that the well-known health benefits of coffee (lower heart disease, Alzheimer's, cancer) may be partly due to its circadian-regulating effect via cortisol. He frames this as a targeted intervention for an aging population whose circadian amplitude has faded. He does not specify a dose, but implies typical coffee consumption.

Land explains that exercise timing is a powerful entrainment tool. He notes that the effect depends on chronotype: for late types, evening exercise can actually advance their rhythm (make them earlier), which is desirable, whereas for early types, evening exercise would delay them further. He recommends morning exercise as a general rule to align with the natural cortisol peak and reinforce a healthy circadian pattern.

Land stresses that artificial light at night is a major circadian disruptor. He recommends practical steps: dimming lights, wearing blue-blocking glasses, using screen filters. He notes that older individuals suffer more because their melatonin production is already low, so blocking blue light is necessary but may not be sufficient; they might need exogenous melatonin.

Land explains that as part of aging, melatonin production drops, contributing to poor sleep. He recommends considering melatonin supplementation as one ages to force higher melatonin levels and maintain oscillation. He also suggests using it for jet lag to quickly realign the circadian clock to a new time zone. He does not specify dosage, but implies it's a standard supplement.

Land states that maintaining a consistent sleep schedule is as important as total sleep duration. Irregular sleep causes circadian disruption and keeps the body guessing, leading to poorer health outcomes. He ties this to the concept of oscillation: regularity amplifies the hormonal swings.

Land explains that eating at consistent times helps the body develop a circadian rhythm around food, which strengthens oscillations. He warns against late-night eating because it misaligns the clocks and impairs sleep and metabolism. This is part of the broader entrainment strategy.

Land explains that the SCN shrinks with age and accumulates waste, reducing free-running circadian rhythms. NAD is the key metabolite that can reverse this degradation. He lists natural ways to boost NAD: calorie restriction, time-restricted eating, exercise, dietary polyphenols, and circadian alignment itself. He also mentions NAD booster supplements as a potential aid, especially for older people who have lower NAD. He emphasizes the bidirectional relationship: improving circadian rhythms also increases NAD, creating a positive feedback loop.

Land explains that circadian rhythms are 24-hour cycles regulating hormones, body temperature, energy, and blood pressure. In youth, there are robust peaks: cortisol high in the morning, melatonin high at night. With aging, these fluctuations flatten—older people have lower morning cortisol and lower nighttime melatonin, leading to a 'flatlined' rhythm. This loss of oscillation means the body doesn't receive clear time-of-day signals, causing chronic jet lag. He cites research showing circadian disruption increases risk of neurodegeneration, cancer, diabetes, obesity, hypertension, and heart disease. The three pillars of circadian health—oscillation amplitude, free-running persistence, and entrainment to environmental cues—all degrade with age, and this degradation accelerates other hallmarks like genomic instability and inflammation. Therefore, he predicts it will be formally recognized as a hallmark within a few years.

He describes that younger people produce a lot of cortisol in the morning to wake up and a lot of melatonin at night to sleep. Older individuals have much lower peaks, resulting in a nearly flat line. Without these hormonal fluctuations, the body's internal clock cannot distinguish morning from night, leading to poor sleep, shorter sleep, higher inflammation, worse metabolic health, and lower energy. He likens it to experiencing jet lag 24/7, which he imagines is what being 80 feels like. This chronic state accelerates DNA damage and inflammation, contributing to age-related diseases.

Land explains that the master circadian clock in the brain (SCN) shrinks and accumulates waste with age, reducing free-running ability. Research shows NAD is a key metabolite that maintains circadian clock robustness. Ways to increase NAD include calorie restriction, time-restricted eating, exercise, dietary polyphenols, and circadian alignment itself. However, the chronic jet lag of aging coincides with NAD reduction, creating a vicious cycle: circadian disruption causes low NAD, and low NAD causes further circadian disruption. Therefore, interventions that boost NAD (like NAD precursors) or improve circadian entrainment can break the cycle and potentially reverse clock degradation.

Land argues that because older people have lower natural cortisol production, bright light exposure alone might not restore a robust morning peak. Caffeine raises cortisol, so consuming it in the morning could provide the necessary 'kick' to anchor the circadian rhythm. He speculates that this mechanism might partly explain why coffee consumption is associated with lower rates of heart disease, Alzheimer's, and cancer. He emphasizes that caffeine should only be consumed in the morning to avoid disrupting sleep.