How Does Poor Sleep Affect Our Health? Genetics Provides New Clues

A genetic study offers new insights into how short sleep duration and insomnia are linked to the risk of developing health problems.

[This article was co-authored by Camille Lassale, researcher at ISGlobal, and Álvaro Hernáez, Associate Professor at the Blanquerna Faculty of Health Sciences - Ramon Llull University and researcher at the Hospital del Mar Research Institute.]

People who get too little or poor-quality sleep tend to have more health problems. Lack of sleep has been linked to cardiovascular diseases, mental health issues, and chronic pain, among many other conditions. But behind these associations lies a harder question to answer: does poor sleep actually help cause these problems, or is it merely a consequence of poorer health?

Our study, recently published in the Journal of Sleep Research, brings new evidence to this question. The results suggest that certain sleep disturbances—especially short sleep duration and insomnia—may directly contribute to the development of various health issues.

This distinction is crucial. Imagine, for example, that we observe people with insomnia suffering more heart attacks. That doesn't necessarily mean insomnia is a cause. People with insomnia might experience higher stress levels, engage in less physical activity, have poorer overall health, or have different social circumstances. All these factors can make two things appear linked without one necessarily causing the other.

Using genetics to better understand the sleep-health link

To try to overcome this issue, we used a genetics-based approach called Mendelian randomisation. Put simply, the idea is to leverage the fact that certain genetic variants predispose people to specific traits, such as sleeping less, being more prone to insomnia, or being a morning person.

Because these genetic variants are randomly assigned at conception, we can use them as a sort of "natural experiment" to examine whether a specific trait influences health.

In our case, we went one step further. Rather than studying a single disease, we systematically analyzed seven sleep- and circadian rhythm-related traits against 702 different health outcomes and conditions. Furthermore, the results from one population were validated in a second independent population, and multiple sensitivity controls were applied to minimize false positives.

The link between short sleep, insomnia, and health

The findings highlighted short sleep duration and insomnia in particular.

Genetic predisposition to short sleep was linked to a higher risk of various neurological and mental health issues, such as attention deficit hyperactivity disorder (ADHD) or neuroticism; musculoskeletal conditions like osteoarthritis and back pain; and other conditions such as asthma or gastroesophageal reflux disease (GERD).

Genetic predisposition to insomnia was also associated with a wide range of problems, notably myocardial infarction, depression, and various joint disorders. On the other hand, predisposition to snoring was linked to higher body mass index, increased low-grade inflammation, and a higher risk of falls.

What is most interesting, however, is that almost all of these associations had previously been observed in observational studies that followed people over many years (here are a few examples). Now, genetics points in the very same direction. When two completely different scientific approaches arrive at similar conclusions, we have stronger grounds to believe that short sleep or insomnia could be one of the underlying causes of some of these diseases. This is likely the most significant takeaway of our work.

Quality sleep to prevent disease

If poor sleep were merely a consequence of ill health, improving sleep might make us feel better, but wouldn't necessarily prevent disease. Conversely, if sleep is one of the drivers leading to these conditions, improving it becomes a potential preventive tool.

We cannot yet state definitively that sleeping better or treating insomnia will prevent a heart attack, depression, or joint disease. What we can do is highlight where sleep interventions are most likely to have a real impact on health. This now needs to be tested in well-designed clinical trials. Quality sleep is a reflection of a healthy lifestyle, but it is very likely also one of the key tools we have to achieve it.