How a mother’s sleep disorder can cause obesity in her children
People normally see their weight as an energy balance teeter-totter with eating at one end of the seesaw and exercise at the other. Energy intake is a fancy word for “eating”, whereas energy expenditure is just a complicated way of saying “exercise”. Obesity arises when, over a long period of time, your energy intake is greater than your energy expenditure — in other words, when you eat more and more and exercise less and less. Seems straightforward, right? Unfortunately, it is not so simple.
Sleep apnea is a disorder in which a person’s breathing repeatedly stops for a short amount of time (30–40 seconds in severe cases) during rest, resulting in oxygen deprivation and potentially a condition called chronic intermittent hypoxia (CIH). A 2013 study at the University of Western Ontario, led by Dr. John Ciriello, found that offspring of pregnant rats exposed to rounds of no oxygen were prone to developing and maintaining obesity from an early age. Basically, mothers with sleep apnea can have children that are more likely to be overweight and stay overweight than mothers without the disorder.
At first glance, these data may seem far-fetched and counterintuitive — how does a lack of oxygen relate to excessive fat buildup? But it’s important to remember that oxygen is an incredibly important ingredient in the make up and maintenance of life, and that the mother is the life source for the unborn child.
When pregnant rats are deprived of oxygen, there is less available oxygen and nutrients for the unborn child to use for growth. If the oxygen deprivation in the mother rat is chronic, similar to sleep apnea, it can lead to restricted growth for the fetus throughout the pregnancy and even in the first few weeks after birth. Examples of restricted growth, for instance, include a smaller number of heart cells.
But restricted growth in early infancy can eventually cause obesity. Ciriello and his team found that after just six weeks the oxygen-starved offspring had more fat mass than rats reared without oxygen starvation, and by week twelve they were heavier than the “normal” offspring. In addition to a larger fat mass and body weight, oxygen deprivation also resulted in the offspring having higher blood sugar and insulin levels as well as impaired glucose tolerance. All of this suggests that children born to mothers with sleep apnea have a predisposition to obesity and of developing metabolic diseases, including Type 2 diabetes, later in life. Ciriello’s study notes that excessive weight gain after birth may be the body’s way of making up for restricted growth in the womb.
Treatments for sleep apnea depend on the severity of the disorder. In mild cases, the condition can be alleviated by sleeping on your side or by using a mouth guard to bring out the jaw line in an attempt to maintain the airway. In severe cases, a continuous positive airway pressure (CPAP) device is recommended, which provides constant airflow.
Ciriello’s findings are bringing attention to the complexities of obesity, and to the fact that the condition results from more than just excess food intake. Already the data have had a large impact on the obesity research community and have been widely cited and covered by major news media. Ciriello’s work also demonstrated the impact that research at Western University has had on the local and global community. Ranked as one of Canada’s top research-intensive universities, Western is at the forefront of neuroscience, imaging technologies, and musculoskeletal health research with $230 million in total research funding in the 2014–2015 year. This is just one of dozens and dozens of studies that have come out over the past few years that emphasize the importance of having a good night’s sleep. The renowned workaholic Arianna Huffington has even come out in favour of sleep in her recent book The Sleep Revolution: Transforming Your life, One Night at a Time. Maybe it is time for all of us to work less and sleep more. What are you waiting for? Stop reading and start snoozing.
This article was written by Grace Jin, an undergraduate science student at Western University. This essay is the product of a science-writing internship in David Smith’s Lab at Western.
