乳癌
加拿大一项医学研究发现，长期值夜班的女性，患乳腺癌的几率会增加。对此，加拿大皇后大学的研究人员对1134名女性乳腺癌患者，以及1179名健康女性的健康资料进行了比较，结果显示，与其他女性相比，夜班工作达30年以上的女性，患乳腺癌的几率增加了两倍，这说明了熬夜对于患乳腺癌有着直接的影响。
除此之外，中国江苏医院妇产科主任医师刘德佩认为，“如果身体长期连续熬夜，加上精神处于紧张状态，将会影响人体内荷尔蒙的分泌，从而抑制脑部松果体分泌褪黑激素，增加患癌概率。”
中医认为，夜晚阳气较弱，阴寒之气较强，如果长期熬夜又不注意夜间防寒，会增加体内的内寒之气，导致经虚血结，这也会间接诱发乳腺癌。
夜晚不睡觉的人
英国科学癌症研究中心研究了世界各地1000多名30至50岁的癌症患者，发现99.3%的人常年熬夜，凌晨之后才会休息。对此专家指出，熬夜一方面会造成生物钟紊乱之外，另一方面，夜间灯光会破坏人体褪黑素形成，而这是保护人体免疫功能的重要一环，缺少它容易让白血病、乳腺癌、前列腺癌等找上门
来。
因此熬夜最好不要超过12点，因为以中医的观点而言，晚上11点至凌晨2点是人体排毒的黄金时期。
Breast cancer
A Canadian medical study found that long-term shift work is associated with a higher risk of breast cancer for women. The researchers at Queen's University of Canada compared 1134 women with breast cancer and 1179 healthy women. The results showed that the increased risk among women who worked 30 or more years of night shift compared with other women who did not, the risk of breast cancer has increased two times. This shows that staying up late has a direct impact on breast cancer.
Liu De Pei, a Chinese physician from Jiangsu Hospital Obstetrics and Gynecology added that, “If a person who is under stress continually stays up late for a long time, the secretion of hormones in the body will be affected, thereby inhibiting the secretion of the pineal hormone melatonin in the brain and this will in turn increase the risk of cancer.”
Chinese medicine believes that the Yang Qi (阳气) is weak at night while the Ying Qi (阴气) is strong. If you stay up late for a long time and ignore the cold at night, the chill of the internal body will increase, resulting in blood clot. This will indirectly lead to breast cancer.
People who do not sleep at night
The British Science Cancer Research Centre has surveyed more than 1000 cancer patients around the world aged 30-50, and found that 99.3% of them stayed up late all year round. Staying up late will disrupt the biological clock. Apart from this, the lights will destroy the formation of melatonin which helps to protect the body's immune function. One is prone to suffer from leukemia, breast cancer and prostate cancer if there is a lack of melatonin.
Therefore, it is advisable not to stay up later than 12 a.m. for according to Chinese medicine, 11 p.m. to 2 a.m. is the golden time for human detoxification.