Why do we feel sicker at night?

Our circadian rhythms plus a sharp increase in immune system activity are contributors

Feeling sicker, or more anxious, at night? You are not imagining it. Your body’s circadian rhythms, and a nocturnal spike in immune system activity, can contribute to an exacerbation of physical, and mental, symptoms.

So why do we often feel sicker at night?

"There are two main reasons," says Prof Andrew Coogan, a behavioural neuroscientist at Maynooth University, who specialises in the study of circadian rhythms and chronobiology. "The first is to do with our biological clocks. One of the things that the circadian clock controls is our immune system. Some of the molecules that cause inflammation are more active at night, and so inflammation and inflammatory pain is worse. The classic example is in rheumatoid arthritis. You will be stiff and sore in the morning.

“The other reason is even more simple. The longer we go into the day the tireder and sicker we are going to be feeling. Then there is when we are feeling ill because of the cold and flu season. All those things are underpinned by the immune system, and how it talks to the brain, and that is modulated by time of day.

“If we’re sick we suffer from this collection of symptoms that we call sickness behaviour. Our mood comes down, we get this sort of brain fog, our attention is lower, our temper is quicker. We sort of withdraw. We don’t want to do stuff. We want to sleep. The physiology – the under the hood stuff – that drives this sickness behaviour is all shaped by our biological rhythms. So we do have a tendency to feel worse later on in the day. And also when we’re feeling tired that will make us feel worse as well. For most people those things come together in the evening and the night. And then, of course, if we can’t sleep that just reinforces the whole cycle.


Sleep deprivation is also linked to pain perception and exacerbates pain, adds Coogan. “Around the time we wake up in the morning our stress hormone cortisol rises. It rises in anticipation of us waking. And that seems to be really important for getting us ready to get up, and how we feel when we wake up. Obviously if we’re up during the night the cortisol is low. We feel more lethargic. We don’t have energy.”

What type of symptoms can be aggravated at night?

People with respiratory conditions, lung disease, and colds and flus, are among the patients who may experience a worsening of symptoms.

"People who have established lung diseases – COPD (chronic obstructive pulmonary disease) and asthma are the two most common – would regularly notice increased cough, wheeze, or shortness of breath at night," says Dr Emer Kelly, respiratory physician at St Vincent's University Hospital. "Some of that is hard to understand, but there is a physical element to it with a lung condition, or bad cold. At night if there's dust, or colder air when the heating goes off, then that can cause the airwaves to be a little bit more reactive.

“Meanwhile, as we see obesity increase, hypoventilation – a lack of ability to breathe effectively at night due to increased weight – is becoming more common.”

Can lying down at bedtime exacerbate symptoms?

Our recumbent position in bed increases some digestive and respiratory symptoms. “When people lie down they can get a sensation of post nasal drip,” explains Kelly. “If they have allergic rhinitis, or sinus problems, or the common cold, they’ll notice secretions from their sinuses dripping down the back of their throat, which is a tough symptom to put up with on its own, but will trigger a cough as well.

“And if some things are coming down when you lie down, others are coming up from the stomach – acid and reflux from the oesophagus. This can be a trigger for things being worse at night for a lot of patients with asthma, or with a pre-existing condition such as COPD. It can be a cause of chronic cough as well. One of the top three causes of chronic cough is reflux.”

How can symptoms be eased at night?

If reflux is the issue Kelly sometimes suggests patients place a brick under their bed’s back legs “because it keeps the whole body at a slight tilt, and everything down in the stomach a bit more effectively. We also commonly recommend to people that they shouldn’t eat within three hours of going to bed, so the stomach is empty.”

Kelly also advises avoiding caffeine and alcohol late in the day “because they will relax the lower oesophageal sphincter. This means that stuff might splash up more easily from the stomach into the oesophagus. This can cause the airways to get a bit hyper-reactive as well. It can cause that wheeze, that kind of spasm in the airways.

“In addition, if somebody is asthmatic or they have COPD it is very important that they take their prescribed inhalers properly.” People with colds can also get a temporary type of asthma. “They may cough as soon as they put their head down on the pillow. If the infection is bad it can be worth checking with their GP if they need an inhaler.”

She also prescribes keeping bedrooms uncluttered “and clear of anything that could predispose to dust. A stability in air temperature – not letting the bedroom get too cold – can also help.”

Taking over-the-counter medications before bedtime may also help. “These remedies don’t shorten the duration of a cold or flu, but they improve symptoms. Some have a decongestant or antihistamine, which can help dry up secretions from the postnasal drip, and allow someone get off to sleep and relax the coughing.”

Meanwhile, Coogan references a study in Berlin of patients with rheumatoid arthritis, which changed their steroid medicine to a long-release formulation taken at night. "When you do that, because it's much more effective at blocking the inflammation during the night, the patients had a lot less stiffness and pain in the morning. It's a really nice example of taking a standard medicine and just changing the time of dosing to match the symptoms, or the mechanisms that produce the symptoms better."

So could taking all medication at night be more effective?

Other research has found that many drugs, including a popular blood pressure drug and some statins, are also more effective when taken in the evening.

Tailoring the timing of treatments to the body clock of patients is known as chronotherapy, explains Coogan. “The focus is not about what medicine you take, but when you take it. Either the therapeutic effect of the medicine, or the side effects, may change depending on when you take the medicine. Some medications are going to be more effective in the evening, some are more effective in the morning.

“This is something that people in oncology, for instance, have been looking at for a while; chemotherapy at different times does seem to reduce the side effects for some people.

"However, there has been very little study of when you take medicine. We should know a lot more about this than we do know. A colleague in Cincinnati just did a big study at a major hospital there. They looked at the peak times of day when patients were given medicine. Those peak times were most likely due to the nursing schedule, rather than when it actually might be best."

Is our mental health also influenced by night?

At Maynooth University research is also being carried out into how chronotherapy may improve outcomes in psychiatric conditions, such as depression and ADHD.

“People are looking at how our mood varies according to the time of day,” adds Coogan. “We wake up in good mood – we get what psychologists call positive affect – and then our mood sort of declines across the day, and people are interested in looking at that, and understand how that looks different in someone who might suffer from depression; where their mood is already low when they wake up.

“Measuring mood is quite difficult because it’s a subjective thing, but then people have looked at Twitter and looked for words that indicate positive affect and words that indicate negative affect, and you can see that there’s more positive affect in the morning, and the tone gets snarkier and more negative later in the day.”

"It can definitely be influenced," says Dr Tom McMonagle, general adult psychiatrist at Tallaght Hospital. "The most obvious example is that people who are depressed feel worse in the morning. People who are depressed classically get what is called early morning wakening, which is where they wake up two hours, or more, before their normal time of wakening. That has to do with circadian rhythms."

How do anxiety and stress affect us at night?

“Anxiety stops you getting to sleep,” explains McMonagle. “Psychiatrists tend to divide sleeplessness into initial, middle and late insomnia. Initial insomnia is classically there from anxiety. You can’t get to sleep. You lie down in bed and all your troubles come to you.

“People who are stressed out for any reason – if they are in pain, if they are in danger, if they’re depressed – they will be in what is called a hyperaroused state, so their sympathetic nervous system, which is their ‘fight or flight or freeze’ system, will be overactive, and that stops you getting to sleep.

“We also have an antagonistic nervous system, called the parasympathetic nervous system, and that one does the opposite; it is about ‘rest, digest, restore, and reproduce’. So when you’re in a nice mellow, warm state you feel relaxed, you digest your meals, and you think amorously. The parasympathetic nervous system is the one that you want to have switched on when you are going to bed.

“Middle insomnia is also usually due to anxiety. Your sleep is shallower when you get it, so you’re more easily woken. And when you do wake, you start to think about all your worries again, and you find it hard to get back to sleep.”

Kelly also notes: “For our poor patients with lung cancer, especially those with advanced disease, and for our patients with COPD, the nights are long. Anxiety and depression are common with people at that stage of disease. Sometimes there is even an anxiety and fear of not waking up that makes them find the nights very difficult.”

Why do problems and worries seem greater at night?

There are a number of reasons problems will loom larger at night, according to McMonagle. “We tend to exist in types of problem-solving networks. We don’t solve all our problems on our own. We usually ask our loved ones, or our friends, or our colleagues. At night you are cut off from your problem solving networks.

“Our problem-solving networks also help to soothe our distress. These are separate things. One is a cognitive thing; other people know stuff that you don’t know. The other is emotional, like when you parent says, ‘don’t worry, everything is going to be alright’, or if you get a hug.

“In mental health we tend to divide coping into problem-focused coping and symptom-focused coping. At its crudest, if somebody is having difficulty at work, problem-focused coping would be changing their job, and symptom focused coping would be going to the pub every night after work.

“So, at night time you are cut off from sources of information that might help with problem-focused coping, and you’re on your own, so you don’t have access to symptom-focused coping; you can’t get a hug or somebody to reassure you.

Any problems that you have are harder to solve at night, either to find the actual solution or to stop feeling so badly about them.

“The final reason is really very prosaic. When you’re in bed at night you’re not distracted. And distraction is a wonderful way of keeping problems out of our heads. We often complain about being too distracted in this day and age but none of us would really want to live in full consciousness of all our problems at all times.

“So night-time, the unavailability of somebody to comfort you, and the lack of distraction, make feelings and problems more intense.”