Longevity Briefs: Can Cold Exposure Slow Ageing?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

The problem:

Environmental and lifestyle factors appear to influence how rapidly we age. While diet and exercise are likely to have the largest impact, there might exist the potential to improve health and lifespan by leveraging other aspects of our environment, one of which is temperature. Limited exposure to both extremes of temperature appear to trigger various biological mechanisms that would be expected to provide health benefits, and there is also a decent amount of research suggesting that regular sauna use can have health benefits, particularly for the cardiovascular system. The effects of cold exposure, on the other hand, are less well understood. This study gives an overview of what we know so far about the benefits of cold exposure, and the challenges that remain.

The findings:

The researchers reviewed existing literature on cold exposure’s impact on health and ageing. They examined studies using various cold exposure methods, including cryotherapy (exposure to extremely cold air for short periods), cold water immersion and cold plunges.

• Inflammation: Studies showed that short-term cold exposure reduces chronic inflammation by modulating the production of cytokines (molecules that regulate inflammation). Cold exposure is associated with a decrease in pro-inflammatory cytokines and an increase in anti-inflammatory cytokines. Whole-body cryotherapy (WBCT) demonstrated significant anti-inflammatory effects in both healthy individuals and in those with conditions like obesity (in which chronic inflammation is increased).
• Oxidative stress: Cold exposure, particularly WBCT, reduced oxidative stress by enhancing antioxidant enzyme activity and reducing reactive oxygen species (ROS) production. Reactive oxygen species are highly reactive molecules produced within our cells that are capable of damaging other molecules like DNA. Regular cold exposure, like winter swimming, was also correlated with increased antioxidant levels.
• Metabolism: Cold exposure activates brown adipose tissue (BAT), a type of tissue that consumes fat in order to generate heat, thereby increasing energy expenditure. It enhances thermogenic capacity (the ability to generate body heat) and improves sensitivity to the blood sugar-lowering hormone insulin. A more recent discovery is the “browning” of fat tissue – white fat can turn into brown fat in response to cold exposure.
• Cardiovascular health: Short-term cold exposure increases venous return and cardiac output in healthy individuals, which might lead to an improvement in cardiovascular health. However, studies comparing different climates suggest that long-term cold exposure may increase cardiovascular disease mortality especially among the elderly. The most likely reason for this is the constriction of small blood vessels to reduce blood supply to the skin and conserve heat, which leads to a rise in blood pressure. The researchers noted a lack of large-scale clinical studies on the long-term cardiovascular effects of cold exposure in humans.

The implications:

The existing research suggests that controlled, short-term cold exposure may offer several anti-ageing benefits including reduced inflammation, decreased oxidative stress, improved metabolic regulation, and potentially improved cardiovascular health. However, we still lack research concerning the effects of different types of cold exposure, particularly prolonged exposure to cold environments. At the very least, prolonged cold exposure may be dangerous for older people and for those with hypertension, while short term cold exposure should not be attempted without supervision.

An exposure that is beneficial at low doses or durations, but harmful at high doses or durations, is known as a hormetic stressor. The general principle behind hormetic exposure is that a stressor that is harmful in high doses may, in small doses, produce adaptive responses that make the body more resilient to stressors in the long term. In the case of cold exposure, for example, short term exposure challenges the body’s ability to maintain its temperature, encouraging adaptations in brown fat tissue that improve the regulation of body temperature long-term. There are quite a few examples of hormetic exposures that are of interest to medicine, including exercise and even radiation.