Our aim was to recruit two groups of people (one group living with psoriasis, and one group free from psoriasis) and measure their sleep quality over a period of 8 weeks, to enable us to look for patterns.
This post takes a closer look at what the research involved, and what we learned.
Why Study Psoriasis And Sleep?
Psoriasis is a long-term inflammatory skin disease, affecting around 2-5% of the population worldwide1. It’s caused by an overactive immune response, resulting in an overgrowth of skin cells, which appear as thickened, scaly red patches of skin, typically on elbows, knees and scalp. In severe cases, it can affect large parts of the body.
We know that psoriasis impacts daily activities in a number of ways, including sleep. Studies have shown that people with psoriasis have a poorer quality of sleep than people without psoriasis2 3, although the reasons aren’t completely clear.
Some research suggests symptoms like pain and itching (sometimes called pruritus) disturb sleep 4 5, but there’s also evidence that medical conditions linked with psoriasis (like diabetes and depression) can play a role6.
CitizenResearch is interested in how people living with psoriasis sleep, because sleep plays a big role in physical and mental wellbeing. There’s also research made in animals which suggest that poor sleep may make psoriasis worse7, so by better understanding the relationship, we may be able to work on tackling the causes.
To help us draw comparisons we looked at sleep quality in both people living with and without psoriasis in what we named “The Sleep Study”.
What were the aims of the “The Sleep Study”?
The aim of the study was to recruit two groups of people (one with psoriasis and one without psoriasis) and monitor their sleep over an 8-week period. Using this information we then planned to look at…
- How many people experienced poor sleep quality
- How many people suffered with insomnia (difficulty falling asleep or staying asleep)
- Possible links between psoriasis severity and sleep quality
- Possible links between itch and sleep quality
When did the study take place?
The study took place between September 2016 and January 2017.
Who took part in “The Sleep Study”?
A total of 525 people (228 with psoriasis and 297 without psoriasis) completed the study in full, answering all questionnaires.
The majority of participants lived in Canada and the UK, with a small number from the USA and other countries. Around 70 per cent of both study groups were female.
The average age of the control group (without psoriasis) was 39.6 years. The average age of the psoriasis group was 47.9 years.
Of the people living with psoriasis (PLWP), almost half (43%) rated their psoriasis as severe. The majority of the group had plaque psoriasis, and on average had been living with psoriasis for 20 years.
About 30 per cent of people in both groups said they had been diagnosed with depression.
What did the study involve?
During sign up, all participants were asked to complete a series of questions to capture their age, gender and bodyweight. People with psoriasis were also asked about the type of psoriasis they have, it’s severity, degree of itching, medications and any other conditions.
Once they had completed the baseline questionnaires, the participants were asked to complete 4 questions about their sleep on a weekly basis, describing how long and how well they had slept.
Once a month, participants were asked to complete a larger questionnaire, about the participants sleep quality, insomnia severity and their itch.
At the same time as the longer questionnaires, people with psoriasis were asked about their psoriasis severity and how much it had affected their quality of life over the past month.
What were the results?
We analysed results from the 525 participants who completed all of the questionnaires over the study period.
In the control group, 79.8%, 79.5% and 77.1% of people had a poor sleep quality at the start, and after month one, and month two of the study respectively.
In the psoriasis group 82.8%, 82.8% and 80.2% had poor sleep quality at the start, and after month one, and month two of the study respectively.
Although average scores were higher in the psoriasis group than the control group at all time points (which suggests poorer quality sleep), they were not significantly different. This means we can’t be sure whether this pattern (people with psoriasis having worse sleep quality) is a real relationship, or just down to chance.
Overall, 6-7 % of participants in both groups were classed as having severe insomnia. In total, 35-40% of participants had some degree of insomnia.
However, there was no significant difference in the levels of insomnia between people with or without psoriasis.
Itching and sleep quality
We measured itch by asking participants how much they have been itching, how bad the itch is, and how it has affected their daily life.
Results showed average ‘itch’ scores were significantly higher in the psoriasis group than the control group at all time points, which is something we would expect.
We also found that psoriasis severity was linked with degree of itching. People with the worst psoriasis reported the highest itch scores.
In people with psoriasis, there was also a link between itching and insomnia. The people reporting the worst itching were also the ones reporting the worst levels of insomnia.
Overall, we found that itching had a much more pronounced effect on sleep quality in people living with psoriasis than in people in the control group.
Psoriasis severity and sleep quality
Results showed self-reported psoriasis severity was positively correlated with both sleep quality and insomnia. This means that as psoriasis severity increased, so did poor sleep quality and levels of insomnia.
What can we learn from the results?
In our study, the overall sleep quality of people living with psoriasis was not significantly worse than people without psoriasis. This might seem surprising given that research shows psoriasis negatively affects sleep, but there are a number of possible explanations.
Firstly, our study advertisements asked for people who were interested in measuring their sleep, or who had problems sleeping, so it’s possible that we attracted a group with a poorer quality of sleep than the general population.
Around one third of the people in both groups reported to have been diagnosed with depression. We know that depression can have a negative impact on sleep, so this may also have impacted the results.
It’s also possible that we didn’t have enough people for us to see a significant difference – average sleep quality scores were worse in people with psoriasis, but not enough for us to be sure if this is a true relationship, or just chance.
However, it may simply be that the link between psoriasis and poor sleep is not always observed8, or that it’s dependent on the severity of psoriasis.
In our study we found that levels of insomnia were the same between people living with psoriasis and the control group. This is consistent with other studies that have not found that insomnia is widespread in both people with and without psoriasis9.
However, the lack of difference might be down to the wide variety of tools generally used in studies to measure insomnia, which makes comparisons between studies difficult10.
We found that itching was much more common in people with psoriasis than the control group.
This is consistent with existing data– in one study of people living with extensive psoriasis, itching was reported by around 85% of the group13. Other reviews have found itching is a symptom in 60-90% of psoriasis patients11.
Our results also showed that in people with psoriasis, the worse the itching, the worse the insomnia. This seems to fit together with existing research which shows that itching mainly occurs in the evening and at night13. It also supports data which shows that itching seems to be a key cause of poor sleep quality in people with psoriasis12 13
In this study we found that in people living with psoriasis, poor sleep quality seems to be driven by itching. The people reporting the worst levels of itching were the most likely to experience the worst levels of insomnia.
This supports existing research which shows treatments which help to reduce itch can be helpful in improving insomnia, where itching is the primary cause of poor sleep14.
However, given that poor sleep quality in psoriasis can be multifactorial (sleep apnea occurring in 36%-81.8% of people with psoriasis15) addressing sleep problems will likely need a variety of approaches according to the different causes.