By Dr.Manvir Bhatia & Ananya-Team NSC

Sleep in itself is a multi-dimensional subject. Good sleep quality depends on a number of factors such as the duration, underlying health conditions, mental state, etc. Lack of sleep can trigger various health factors, cancer being one of them.

Cancer affects the body in various ways. During treatment, an individual might suffer from depression, anxiety, digestion problems, breathing issues, deep fatigue, etc. All of these accompanied with pain makes it very difficult for one to get good quality sleep.

Lack of Sleep and Cancer:

Along with good mental and physical health, sleep is also important to prevent various chronic diseases, cancer being a major one. Insufficient sleep is associated with development of colon polyps which have the potential to get cancerous. Reduced sleep is also tied to increased incidence of stomach cancer. It is to be noted that excessive sleep (>9 hours) can also increase the risk of cancer. While it’s well-established that insufficient sleep can have negative effects on overall health, including the immune system, the relationship between lack of sleep and cancer is complex and not fully understood. It’s important to note that saying lack of sleep directly causes cancer might be an oversimplification. Rather, inadequate sleep is associated with factors that could contribute to an increased risk of cancer.

The circadian rhythm, the body’s internal clock that regulates various physiological processes, including sleep-wake cycles, is closely tied to the release of hormones like melatonin. Disruptions of the circadian rhythm, such as those caused by irregular sleep patterns or night shift work, may impact the body’s ability to regulate cell division and repair DNA damage, potentially increasing the risk of cancer.

Sleep deprivation can disrupt the balance of hormones in the body, including those that regulate appetite (leptin and ghrelin) and stress (cortisol). These hormonal imbalances may contribute to factors associated with cancer development.

According to a study by the American Association of Cancer Research, night shift was associated with several forms of cancer in women. It demonstrated that women who were working night shifts were at 41% of increased risk of skin cancer and 33% increased risk of breast cancer. They also found that the risks of breast cancer increases by 3.3% with every 5 years of night shift. Also, frequent disturbance in sleep at night or difficulty in falling asleep especially due to screen light puts one at a higher risk of breast cancer. The possible reason behind this can be the decrease in the levels of melatonin due to light which increases the levels of circulating oestrogen in the system disrupting the oestrogen signalling pathways. Melatonin itself can suppress tumours. Thus, a decrease in its levels is an advantage for tumour growth.  

Sleep is also very crucial for a well-functioning immune system. Chronic sleep deprivation or poor-quality sleep may weaken the immune response, making the body less effective in identifying and destroying cancerous cells.

Factors that affect sleep quality in cancer patients:

Patient age:

The suprachiasmatic nucleus in the hypothalamus regulates the melatonin levels in our body. Melatonin is a hormone associated with sleep. Increase in age accompanied with cancer can significantly decrease the levels of this hormone thereby affecting the homeostatic sleep regulation and circadian rhythm. This ultimately results in poor sleep quality.    
Occurrence of cancer at an older age disrupts sleep more as compared to young cancer patients.

Pain intensity:
Pain is a very common symptom among cancer patients. This probably is due to the dysregulation of dopamine in the brain. Pain causes a disruption in the signalling of dopamine. This can lead to prolonged periods of sleep loss and disturb sleep continuity. There is a reciprocal association between sleep disturbance and pain as the lack of sleep has the capacity to intensify the pain levels.   

Depressive Symptoms :
According to a study by Endeshaw et al., the odds of disturbed sleep are more in individuals with symptoms of depression. Depression leads to deficiency in key neurotransmitters like serotonin, acetylcholine and noradrenaline. This causes a disruption in the homeostatic and circadian rhythm leading daytime sleepiness and consequently fragmented sleep at night. Lack of sleep also intensifies the development of depression. Thus, both sleep and depression have a bidirectional relationship.

Location of Cancer :

Patients who are suffering from metastatic cancer have a very high chance of multiple organ failure. Thus, the individual has to make major lifestyle modifications to cope up with the situation. They have to spend long hours in bed with reduced daily activities.This majorly disrupts their sleep wake cycle and makes it very difficult to fall asleep at night. Also, with distant metastasis, the treatment is more intensive as compared to a localised cancer. This comes along with a number of side effects, improper sleep being one of them.   

Anxiety :

Anxiety is an effect that comes along with cancer right from the start of diagnosis to the end of the treatment and even after that. Being screened for this, waiting for the results, confirmation of diagnosis, treatment cycles and worrying about its recurrence, all of it is accompanied with a lot of anxiety and distress. This leads to a mental state that has a very detrimental effect on sleep.

Cancer Treatment :

Chemotherapy and radiotherapy leads to the production of proinflammatory cytokines that act on the central nervous system which influences sleep negatively. It also leads to symptoms like fatigue, numbness, nausea, vomiting etc. that makes sleeping a very difficult task for an individual.

Hence, we conclude that cancer and sleep are deeply intertwined. This also highlights the importance of regular sleep. Also, it is very important to note that sleep, pain and mental health should find a special place in case of cancer treatment to alleviate this condition. Targeting one can positively impact the other. For example, treating depression might improve sleep quality, and addressing sleep problems may relieve this psychological morbidity.  In addition, it is very important to be mindful of your sleep patterns and their overall impact on your health. It is advisable to discuss these with a healthcare professional so that They can provide personalised guidance and strategies to improve sleep hygiene and overall well-being. In addition, the present day lifestyle patterns need to be thought through. Chronic exposure to light without a time cap at all, need for night shifts and an unhealthy routine causes a disruption in sleep heading ahead to cancer risk. Thus, there is a need for well thought policies and strategies to prioritise sleep to improve the health and quality of life of each and every individual. 

References:

https://www.cancer.gov/about-cancer/coping/feelings/anxiety-distress-pdq
https://together.stjude.org/en-us/diagnosis-treatment/side-effects/sleep-disorders.html

White, A. J., Weinberg, C. R., Park, Y. M., D’Aloisio, A. A., Vogtmann, E., Nichols, H. B., & Sandler, D. P. (2017). Sleep characteristics, light at night and breast cancer risk in a prospective cohort. International journal of cancer, 141(11), 2204-2214.

Endeshaw D, Biresaw H, Asefa T, Yesuf NN, Yohannes S. Sleep Quality and Associated Factors Among Adult Cancer Patients Under Treatment at Oncology Units in Amhara Region, Ethiopia. Nat Sci Sleep. 2022;14:1049-1062

https://doi.org/10.2147/NSS.S356597

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