- A British study found evidence that a preference for mornings was linked to a small protective effect on breast cancer risk.
- Although the size of the effect is slight, results indicate need for further research into reducing stress on people’s biological clock.
- There may be more advantages to being a morning person than waking up early.
Medically reviewed by Jennifer A. Ligibel, MD
There may be more advantages to being a morning person than waking up bright-eyed and eager to take on the day.
In a recent study involving nearly 400,000 women, British researchers found evidence that a preference for mornings was associated with a slight reduction in breast cancer risk. Although the effect was very small, investigators say the findings should spur more research into how stresses on people’s biological clock can be reduced.
The study represents a departure from previous research into sleep and breast cancer risk, which has focused on the potentially adverse effects of night shift work and exposure to light at night. The new paper, by contrast, is concerned with factors that people may find harder to change — a personal preference for morning or evening.
The investigators drew on data from the UK Biobank, a research project that has tracked the health of a half million people since the early 2000s. Participants completed questionnaires about their socioeconomic status, lifestyle and environment, early life and family history, and health and medical history. They were asked whether they preferred the morning or evening, and their answers were used to determine their “chronotype.” (Chronotypes, like personality types, are a way of categorizing people. A person’s chronotype reflects the times of day that he or she is most alert and energetic.) Investigators then correlated the chronotype data with data on participants who developed invasive breast cancer.
The analysis showed that women with a morning preference had a less than 1% lower risk of breast cancer than women with an evening preference. That translates into fewer than 10 women in 1,000.
In an editorial on the study, Eva Schernhammer, a professor in the department of Epidemiology at the University of Vienna, wrote that the findings point to “a need for future research exploring how the stresses on our biological clock can be reduced. This offers a tremendous opportunity for preserving good health, achieving healthy aging, and, more specifically, for developing new personalized strategies for reducing the risk of chronic diseases associated with the circadian [biological clock] system…This line of research could also help to align working hours with chronotype — to more closely match externally imposed timing with individual [daytime] preference, especially in the working population.”
There are many factors that can influence breast cancer risk, some of which are under an individual’s control and some of which are not. In the first category are:
- Physical activity
- Hormone use
- Reproductive history
- Alcohol use
In the second are:
- Breast density
- Family history of breast cancer
- Inherited genetic mutations
- Previous treatment with radiation therapy
The Centers for Disease Control and Prevention offers an extensive list of such factors and how they can be managed.