Chronic Cough and Obstructive Sleep Apnea

There is a review article in the Journal of Clinical Sleep Medicine about a relationship between chronic cough and obstructive sleep apnea (OSA). Chronic cough is a significant problem, and in non-smokers, is usually due to post-nasal drip (now called upper airway cough syndrome), gastroesophogeal reflux disease (GERD), or cough-variant asthma.

The authors discussed a couple of cases where patients with chronic cough were diagnosed with OSA, treated with CPAP, and their chronic cough improved dramatically. The authors speculate that OSA could be associated with chronic cough by being related to the reasons patients get post-nasal drip, GERD, or cough-variant asthma. GERD and OSA have already been associated by prior studies. OSA can result in inflammation of the upper airway, which could contribute to post-nasal drip. Finally, studies are showing a relationship with asthma and OSA. Also, OSA by itself has been associated with airway inflammation, be it from repetitive oxygen drops, direct trauma from vibrating tissue, or from the bloodstream. This inflammation could result in chronic cough. So if you have a chronic cough, talk to your doctor about being evaluated for obstructive sleep apnea.

Sleep Duration, Disinhibited Eating, and Weight Gain

Studies have been linking short sleep duration and weight gain in children and adults. Increased food consumption is thought to be responsible for this - short sleepers have more time awake to eat, especially at night. However, there is great variability in weight gain amongst short sleepers. A study was published in the Journal Sleep about short sleepers, disinhibited eating habits, and weight gain. Disinhibited eating examples include eating in response to a negative mood (emotional eating), overeating when others are eating, not being able to resist eating, and overeating because the food tastes good, rather than because of hunger.

The study participants consisted of 276 adults, aged 18 - 64 years old, who were followed for six years. They were nonsmokers, had stable body weight over the 6 months preceding testing, and have no metabolic disease (like diabetes or high blood pressure) or be on any medication that could confound the results. The participants were asked how many hours they slept per night, and divided into short sleeper (<6 hours per night), average sleeper (7-8 hours per night), and long sleeper (>9 hours per night). Disinhibited eating behavior was assessed via a validated eating questionnaire.

The results showed that those participants with high disinhibited eating patterns significantly increased their risk of overeating and gaining weight if they also had short sleep duration. As expected there was a relationship between increased total amount of food eaten and high disinhibited eating pattern. Interestingly, this relationship was only seen in short sleepers, and not seen in average and long sleepers.

Sleep Timing, Weight Status, and Activity Patterns in Children

Studies have indicated a relationship between short sleep duration and obesity in children and adults. The cause of the elevated weight in short sleepers is not known. There is relatively little research done on the relationship between the timing of sleep, weight, and activity patterns. In the Journal Sleep is a study about this topic. The researchers classified sleep timing as early to bed / early to rise, early to bed / late to rise, late to bed / early to rise, and late to bed / late to rise. They studied Australian children ages 9 - 16 years old, and surveyed their sleep habits, physical activity, and measured their weight, height, and waist circumference.

The results showed children who were late to bed / late to rise were 1.5 times more likely to be obese, 1.8 times to have too little physical activity, and 2.9 times more likely to have excessive use of computers and television (a.k.a. screen time) than the early to bed / early to rise group. Interestingly, the greatest differences in the above measurements were between the late to bed / late to rise and early to bed / early to rise groups, which slept the same amount per night. There was little difference in early to bed / late to rise and late to bed / early to rise, which had an average total sleep time difference of over 2 hours per night. This is contrary to the prior studies that suggest sleep duration is linked to obesity. The results from this study imply that it is the timing of the sleep, not the sleep duration, that is associated with obesity.

Some advocate that adolescents be allowed to stay up late and sleep in, including later school start times. However, this might make the obesity problem even worse, according to the study results. If anything, this study suggests that children should be put to bed earlier and gotten up earlier.

Exercise and Obstructive Sleep Apnea

A few, small studies have shown that regular exercise can reduce the severity of obstructive sleep apnea (OSA) as determined by the number of times the upper airway collapses per hour of sleep (AHI). There is an article in the Journal Sleep where researchers studied the effect of a 12 week moderate-intensity exercise program on the AHI in patients with OSA.

There were 43 study participants, ages 18-55 years old with at least moderate severity OSA and who were overweight with a body mass index of >25. The participants also were sedentary, on stable medication dosages, and not being treated for OSA. At baseline, participants had an overnight sleep study, evaluation of body fat composition, pulmonary function tests, and respiratory muscle strength testing. They also wore a home sleep study wrist watch, called an actigraph, for about a week. The participants were then randomized to 12 weeks of exercise training including resistance and aerobic components, or to a stretching only control group. The baseline measurements were than repeated after completion of the 12 weeks.

Results showed that when compared to the stretching only control group, exercise training did moderately improve the AHI. More specifically, 25% were considered a treatment success (based on AHI reduction of at least 50%) and 63% reduced their AHI by at least 20%. And these reductions in OSA severity occurred despite no change in body weight. However, the exercisers did reduce their fat composition by over 1%. Since overweight individuals with OSA can have extra fat in their neck that contributes to upper airway collapse, a reduction in neck fat could explain how the exercisers reduced their OSA severity despite not losing any weight.

Relationship Between Food Intake and Sleep Pattern

Studies have shown a link between short sleep duration and obesity, but few studies have researched food intake and sleep patterns. There is a research study in the Journal of Clinical Sleep Medicine that analyzed the correlation between food intake and sleep patterns in healthy individuals. They studied 52 healthy, non-obese individuals ages 19 - 45 years old who were sedentary, not taking medications, non-smokers, and who spent regular times in bed at night.

Their food intake was determined by a self-report food diary for 3 consecutive days preceding a sleep study. The results showed that none of the 52 participants had any sleep disorders. Analysis of the data showed that food intake, mainly in the evening period, was correlated with several variables related to sleep patterns. More specifically, higher food intake close to bedtime was associated with decrease sleep quality, especially in women. Women took longer to fall asleep if they ate high fat and carbohydrate meals before sleeping. Also, eating a high fat meal close to bedtime decreased dream sleep. The authors speculated that a full stomach could make it more difficult to sleep.

New Treatment for REM Sleep Behavior Disorder

REM Sleep Behavior Disorder (RBD) is a form of sleepwalking where patients will enact their dream while asleep. This dream enactment behavior is not normal, as usually we are completely paralyzed while dreaming. If RBD occurs, patients can accidentally hurt themselves or their bedpartner while sleeping. RBD can occur during certain neurological disorders like Parkinson's Disease. RBD usually responds to a medication called Klonopin, but not every patient finds it beneficial.

A study was published in the Journal of Clinical Sleep Medicine about a non-medicine treatment of RBD. The study authors note that some patients with RBD wake up easily to bedpartners voice when they start moving while dreaming. This stops the potentially injurious behavior and results from the fact that dream (or REM) sleep is a very light stage of sleep, and all of us are easily awoken from that stage of sleep.

In this study, researchers attached a bed alarm to the torso's of four patients with RBD. When the patient tried to sit up while dreaming, the alarm was triggered and a taped recording of the bed partner's voice would calmly tell them to wake up. The results showed that all four patients had a dramatic reduction in dream related behaviors and injury. None of the patients felt it was a burden to use the alarm and they felt it reduced their anxiety about going to bed because they knew they would not likely hurt themselves or their bedpartner while asleep.

This form of therapy would not work in traditional sleepwalking, which occurs out of slow wave (or deep) sleep. In fact, such an alarm is likely to worsen traditional sleepwalking. Therefore, it would be best to use it only for RBD.

Loneliness and Sleep

There is an interesting article in the November edition of the Sleep Journal about the relationship between loneliness and sleep. The study authors describe a previous study that showed that loneliness was associated with more frequent awakenings, but not with the total duration of sleep. The authors feel this makes sense from an evolutionary perspective, as humans may wake up more frequently to ensure safety if sleeping alone.

The study participants were Hutterites, a communal group from South Dakota that sound similar to the Amish. They chose this group because they may be among the most socially connected group in the United States. Eligible participants were at least 19 years old. The study authors recorded the participants' subjective reports of loneliness, depression, anxiety, stress, sleep quality, and daytime sleepiness. Actual sleep duration and number of awakenings was measured for 7 continuous days via a home sleep study device called an actigraph. Actigraphy does not actually measure sleep, but it is a good correlate to an actual sleep study done in a sleep lab. Also, actigraphy can not rule out sleep-fragmenting disorders like sleep apnea or periodic leg movements.

The results showed that perceived loneliness was associated with more awakenings at night as measured by the actigraph. Interestingly, loneliness was not correlated with subjective increase in awakenings or sleep duration, and it was not significantly associated with actigraph-derived sleep duration. The effect of loneliness persisted even when controlling for negative affect (depression). Also, loneliness was not associated with increase report of subjective daytime sleepiness.

The authors point out that the results do not determine if loneliness causes worse sleep or if worse sleep contributes to loneliness. It could be that multiple awakenings lead to more loneliness, rather than the other direction. This is because depressive feelings were not associated with sleep fragmentation. Also, it is the perception of loneliness that is associated with sleep fragmentation, rather than marital status and number of family members the participants reported. This means that even if someone was married and had plenty of social relationships, they would still have more fragmented sleep if they felt lonely.