How to Prevent and Reduce Jet Lag By Determining and Adjusting Your Temperature Minimum
What is Jet Lag and When Does it Occur?
Time zone jet lag is the inability of local sunlight and local darkness to match our internal rhythm. Jet lag is very harmful for our health and will shorten our life. This is because our brain is not made to suddenly be shifted to a drastically different time zone. Some people can easily deal with jet lag while others suffer substantially. Typically, the negative symptoms of jet lag get worse as we age. This is because we become more vulnerable to variations in our circadian rhythm.
It is harder to acclimate to a new time zone when traveling eastward compared to westward. The reason for this is because it will require you to fall asleep earlier than you would normally. This is generally harder to do compared to staying up for longer. If you travel north or south, you will not experience jet lag as you stay within the same time zone. However, you will likely experience travel fatigue because of the process of travelling itself.
The Negative Consequences of Jet Lag On Health
Human beings are a diurnal species (as opposed to nocturnal species) as we are designed to be awake during the daytime and asleep at night. Deviating from this genetical predisposition of daytime wakefulness will cause serious negative mental and physical health consequences. These include depression, amnesia, dementia, mood swings, headaches, gastrointestinal problems, daytime fatigue, reduced alertness etc. This is why we feel miserable because of jet lag and/or shift work. Because our body is genetically not designed for it. Ideally you want to get as much exposure to sunlight while you are awake and as little during the time you are asleep.
What is Our Temperature Minimum and Why is it Important?
Temperature is the effector of the circadian rhythm. This is because our internal clock sends signals to all parts of our body through temperature. Our core body temperate starts rising when we wake up. It peaks after around 11 hours of wakefulness, after which it will start to decline. In order to reduce the negative consequences of jet lag it is highly recommended to find out when your temperature minimum occurs. The temperature minimum is the specific time in every twenty-four-hour cycle when our body temperature is the lowest. Generally, this occurs 90 to 120 minutes before our average waking time. The temperature minimum is the absolute reference point for shifting our circadian rhythm and for reducing jet lag.
The Difference Between a Phase Advance and a Phase Delay
If we expose our eyes to bright light in the four to five hours after our temperature minimum, our circadian clock will shift earlier. This is called a phase advance. In the subsequent days you will tend to get up earlier and go to sleep earlier. On the other hand, if you expose your eyes to bright light in the four to five hours before your temperature minimum, you will phase delay your clock. Consequently, you will wake up later and fall asleep later in the following days. More information on the impact of light exposure on our circadian rhythm and how it impacts sleep can be found on the page focused on Light Exposure.
An Effective Method to Shift Our Internal Clock and Prevent Jet Lag
By knowing the timing of your temperature minimum you can shift your circadian rhythm. This is done predominantly through light exposure within a 4–5-hour window of your temperature minimum. This is a powerful mechanism which you can utilize to prepare your internal clock for traveling to a new time zone. As such, you can prevent the negative effects of jet lag. Studies indicate that by using this technique you are able to shift your circadian rhythm by one to three hours a day.
How to Use This Technique Effectively
It is recommended to use this method in the days before you will be travelling to a drastically different time zone. If you have already arrived at your destination it will likely be too late. This is because you will be unable to adjust your internal clock through sunlight exposure because of two reasons:
- You will get sun exposure during the circadian dead zone when the sun sits high in the sky. This does not have any impact on your circadian rhythm.
- You will unknowingly expose your eyes to sunlight within the 4–5-hour window before your temperature minimum. This will cause your circadian rhythm to shift even further in the opposite direction aggravating the symptoms of jet lag.
It is therefore important to know and monitor your temperature minimum once arrived at your new destination. The best way to this is by keeping track of the time back home and calculating your average waking time during the past couple of days. Additionally, you can use temperature monitoring and tracking devices specifically designed for this purpose. Examples of these temperature tracking tools can be found on the Sleep Tech page.
Other Methods to Manage Our Temperature Minimum and Prevent Jet Lag
There are additional methods to help facilitate the adaptation to a new time zone and preventing jet lag. These include cold/water exposure and exercise.
Taking a Hot or Cold Shower
You can also shift your circadian rhythm by adjusting your internal temperature directly by taking cold/hot showers. For example, if you take a hot shower early in the morning this will reduce your core body temperature. Consequently, this will phase delay your circadian rhythm. On the other hand, taking a cold shower in the morning will increase your body temperature. This will phase advance your circadian rhythm. This is because a cold shower in the morning will cause your peak temperature to be earlier in the day. Consequently, this will make you fall asleep faster at night.
Timed Exercise
Exercise has a similar effect as taking a cold shower as it increases your core body temperature. That is why you should generally avoid exercising late at night as this will shift your circadian rhythm later. This is because your internal clock assumes it is still day or believes days are getting longer. As a result, you will wake up later the next day.
Combining Both Methods For Higher Effectiveness
If you have an upcoming trip planned to an earlier time zone (westward) you would want to shift your circadian rhythm later. In this situation you can combine both methods for maximum effectiveness. In that case it would be beneficial to exercise and/or take a cold shower late in the evening as well as taking a hot shower in the morning. Vice versa if you are travelling to a later time zone (eastward). In that case it would be beneficial to exercise in the morning, followed by a cold shower as well as taking a hot shower in the evening.
The Importance of Nutritional Timing to Help the Adaptation to a New Time Zone
Once you have arrived at a new time zone it is important to eat according to the meal schedule of the new time zone. The worst thing you can do is eating according to the meal schedule you had back home. This will cause your liver to send conflicting signals to your internal clock. This will disrupt the adaptation process to the new time zone.
Important Information When Taking a Short Trip to a Different Time Zone
A final recommendation relates to taking shorter trips to destinations with significantly different time zones. If the duration of your trip is only 72 hours or less, it is recommended to stay on your home schedule. This is important to prevent the negative effects of jet lag when coming back home.
In this situation it can be helpful to make use of different sleep related products. Examples include sleepmasks, blue light blocking glasses and artificial light producing tools. These will allow you to regulate your light and dark exposure according to your time zone at home. As a result, this will prevent your circadian rhythm from being significantly disrupted. Examples of such useful sleep related products readily available on the commercial market can be found on the Sleep Tech and Sleep Related Products pages.
An effective way to reduce the negative effects of blue light on your biorhythm is by wearing blue light blocking glasses. Choosing the right pair of glasses can be overwhelming as there are so many options available on the market. But don’t worry, we’ve made your life easier. Check out our full guide on the 7 Best Blue Light Blocking Glasses to Prevent Insomnia and Sleep Better At Night.