Susceptibility to cold

Introduction

We all want to keep as warm as possible during the winter months. Some of us always seem to feel chilly, whilst others can brave the cold weather in a t-shirt! But why do some people feel the cold more than others?

If you’re always cold, come rain or sunshine, it might be the influenced by your genes. The genes you inherited from your biological parents can impact whether or not you are more susceptible to feeling cold.

Similarly, if you’re the type of person that can wear shorts in the middle of winter,  it could be your genes that are giving you this apparent “super-power”. In this report, we discuss some of the genes involved in cold weather susceptibility. 

Adapting to cold weather

Studies reveal that early humans evolved in Africa for millions of years. During this period they lived in a warm-weather environment. However, following the dispersal from Africa (50,000-70,000 years ago), humans have adapted to live in various world regions, including in high latitude climates and environments that are extremely cold [1] Jump to reference section: [1] .

If the inhabitants of these regions survived extremely cold temperatures, it must have been due to genetic changes that favourably adapted them to these conditions. 

The genetics of feeling cold

Genetic factors that determine susceptibility to cold weather, or lack of it, are related to body processes that;

• Generate and store heat energy

• Control cold temperature sensations. 

While research on this topic is in its infancy, studies have consistently identified variants of three genes to be abundant among populations living in extremely cold climates compared to those living in warmer areas.

These genes are the transient receptor potential melastatin 8 (TPRM8) gene, alpha-actinin 3 (ACTN3) gene, and fatty acid-binding protein 2 (FABP2) gene.

The role of TPRM8 in cold susceptibility

The transient receptor potential melastatin 8 (TRPM8) gene is located on the human chromosome 2. This gene is involved in the formation of molecular mechanisms that interpret cold weather sensations, and its functions are related to the effects of cold temperature.It controls nerve sensitivity to cold conditions, how the respiratory system responds to cold conditions, and the breakdown of blood fats to release heat [2] Jump to reference section: [2] .

The presence or absence of the rs10166942 form of the gene has been associated with cold weather resistance and adaptation and this variant is more common among populations in cold northern climates than in the warm regions of the world. For example, this variant is present in 88% of the Finnish population, and only 5% among the Nigerian population [3] Jump to reference section: [3] .

Having this variant increases the sensitisation (adaptation) of the skin to cold temperature, a condition known as allodynia. In turn, the nerves of the skin become more sensitised, making an individual more resistant to cold temperatures [4] Jump to reference section: [4] .

The role of ACTN3 in cold susceptibility

Alpha-actinin 3 (ACTN3) gene is one of the ACTN genes which regulate muscle contraction. Over 1.5 billion people in the world do not have a functional ACTN3 gene because of a genetic change that causes dysfunctional variants (or mutations) - known as 577X or rs1815739.

This dysfunctional variant has been traced among ancient populations that migrated into colder regions in Europe from Africa. Studies have confirmed that the variant is associated with an efficient mechanism of preserving heat energy in muscles in extreme cold, instead of shivering and losing heat [5] Jump to reference section: [5] .

In turn, these individuals are less susceptible to cold weather. Interestingly, this variant is common in cold climate inhabitants and scarcer among populations in warmer climates. However, the exact statistical impact of this variant is yet to be determined.

The role of ACTN3 in cold susceptibility

The fatty acid-binding protein 2 (FABP2) gene rs1799883 is located on human chromosome 2. The gene controls how the body stores and transports fat molecules.

Studies have shown that it’s more common for individuals living in higher latitudes, such as the Eurasian region, to have the ‘T’ version of the gene compared to those living in lower ones.

The ‘T’ version increases total body fat content, thereby increasing the availability of fuel the body can use for the production of heat. Body fat is also known to prevent heat loss, keeping the body core warm even in cold temperatures [6] Jump to reference section: [6] .

For this reason, individuals with the ‘T’ version of variant rs1799883 have developed cold-weather tolerance. Studies are still ongoing to establish the exact statistical impact of this variant on how we react to cold weather.

Are there non-genetic reasons why I feel the cold more than others?

Yes, there are other reasons why a person could feel colder than others - even in the winter. Naturally, women are more likely to feel cold compared to men, as women generate less energy at rest [7] Jump to reference section: [7] .

If you are experiencing a persistent cold feeling, it could also be due to an underlying health condition, such as anemia, hypothyroidism, atherosclerosis (narrowing of blood vessels), diabetes, low body weight, or poor circulation of blood to the limbs. Additionally, the deficiency of certain vitamins involved in converting nutrients into energy such as vitamin B-12 may make you more susceptible to cold.

What can you do about it?

If you are always feeling the cold more than others around you, the first thing you can do is warm up by putting on extra clothing layers, wrapping up in a blanket, and increasing heat sources.

Secondly, a healthy diet with plenty of fruits and vegetables could help reduce cold susceptibility due to vitamin deficiency. If you persistently feel cold, it’s a good idea to visit a doctor to check-in and help you treat any underlying condition that could be causing you to feel chilled.