Even Mildly Insufficient Sleep Linked to Depression

BOSTON — Although past research has shown a link between severe sleep dysfunction and psychological symptoms, new research suggests that even mildly insufficient sleep duration can have an adverse effect.

Examining data from a nationwide telephone survey of more than 20,000 adult participants, the investigators found that each hour of additional sleep was significantly linked to a decreased risk for symptoms of depression, hopelessness, nervousness, and feeling restless or fidgety.

On the other hand, too little sleep was associated with a higher risk for each of these adverse outcomes compared with optimal sleep (defined as 7 to 9 hours per night).

In addition, "getting just 1 hour less than the optimum sleep duration was associated with 60% to 80% increased odds of each of these symptom," lead author, Kelly L. Sullivan, PhD, assistant professor at Georgia Southern University, Statesboro, said during her presentation here at the American Academy of Neurology 2017 Annual Meeting (AAN).

Dr Kelly L. Sullivan

Dr Sullivan later told Medscape Medical News that she was surprised at how robust that last finding was. "You have one sleepless night, you can rebound. But when you're chronically having challenges where you can't get sufficient sleep, we all feel those effects," she said.

"Having that confirmed in these data is, I think, eye-opening for providers to really understand how there could be this potential to make an impact and to not to discount even mild sleep complaints."

Unique Dataset

Although sleep disorders overall are common in patients with depression and/or anxiety, "the association of small sleep deficiencies while controlling for other risk factors in a general adult population has not been examined [before]," write the investigators.

"We have so much consistent literature looking at mood disturbances and sleep disorders, but so often they focus on extreme sleep deprivation, which is sometimes clinically induced," said Dr Sullivan.

In the current study, "looking at a real population was unique. But also, having that continuous data where we can look at more mild sleep disturbances was a great opportunity," she added.

The researchers examined data for 20,851 participants (50.4% women; mean age, 47.5 years) in the 2012 Behavioral Risk Factor Surveillance System. This telephone survey from the Centers for Disease Control and Prevention asked adults about a wide variety of health topics, including sleep habits, exercise, and demographic characteristics. "So it is based on self-report," noted Dr Sullivan.

The participants were asked how many hours of sleep they normally get in a 24-hour period, including napping. They were also asked whether they specifically felt nervous, hopeless, restless/fidgety, or depressed without being able to cheer up during the previous 30-day period — and how many days their mental health was "not good."

Optimum sleep (7 to 9 hours per night) was reported by 60.6% of the participants, "low but acceptable" duration (6 hours) was reported by 23.8%, and insufficient sleep (5 hours or less) was reported by 12.9%.

After adjustment for factors such as age, sex, race, and body mass index, "sleep duration was inversely associated with number of poor mental health days," report the investigators, with an estimate of –0.80 (95% confidence interval [CI], –0.94 to –0.66).

They found that each additional sleep hour over optimal sleep was associated with decreased odds for each adverse mood outcome asked about.

Table 1. Risk for Outcomes With Each Additional Hour of Sleep Over Optimal Sleep

Outcome	Adjusted Odds Ratio (95% CI)
Depression	0.77 (0.73 - 0.80)
Hopelessness	0.79 (0.76 - 0.82)
Restlessness	0.75 (0.72 - 0.77)
Nervousness	0.80 (0.77 - 0.82)

"I think it's important to point out that these are based on 1-hour changes in sleep. So it could really compound over several hours," Dr Sullivan noted.

In addition, both too little and "mildly insufficient" sleep were significantly associated with greater risks compared with optimum sleep.

Table 2. Risk for Outcomes in Too Little, Mildly Insufficient Sleep vs Optimum Sleep

Outcome	Adjusted Odds Ratio (95% CI)
≤5 vs 7 - 9 hours of sleep per night
Depression	3.91 (3.39 - 4.52)
Hopelessness	3.17 (2.75 - 3.67)
Restlessness	3.93 (3.44 - 4.49)
Nervousness	3.11 (2.72 - 3.56)
6 vs 7 - 9 hours of sleep per night
Depression	1.79 (1.5 - 2.1)
Hopelessness	1.68 (1.4 - 1.9)
Restlessness	1.76 (1.5 - 2.0)
Nervousness	1.61 (1.4 - 1.8)

Women who had 6 rather than 7 to 9 hours of sleep per night had greater risk for each adverse outcome than men, especially for feelings of being depressed. They also had a greater inverse association between good sleep duration and number of poor mental health days.

The overall findings show "unique insight into the association of psychological symptoms and mild sleep deficiency," said Dr Sullivan, who reiterated that low but acceptable sleep of 6 hours was reported by almost a quarter of their large patient population. "So it's quite common."

Study limitations cited, however, included that the influence of other comorbidities or medications was not examined. And Dr Sullivan stressed that sleep quantity doesn't necessarily equal quality. Also, she noted that their observations need to be further assessed in prospective studies.

"Opportunities to Open Doors"

"Dr Sullivan reminded us of some adverse effects from deficient sleep," official discussant and session co-moderator Michael S. Jaffee, MD, Department of Neurology at the University of Florida at Gainesville, said to attendees after the presentation.

"I was actually quite struck by the data she collected, and the robustness of just 1 hour of missing sleep. That seemed to be pretty dramatic, with the 60% to 80% increased risk," said Dr Jaffee.

His fellow co-moderator, Bradley Vaughn, MD, Department of Neurology at the University of North Carolina, Chapel Hill, told Medscape Medical News that it's important to remember that survey studies rely on an individual's perception. "So I hope we don't try to generalize one domain to multiple domains; that's the one caveat to this."

Dr Vaughn added that the factors are bidirectional.

"We know that when patients come in with mood issues or complaints, we need to ask about sleep; and in the same sense when they come in with sleep complaints we need to ask about mood. I think both are opportunities to open doors to explore underlying issues," he said.

Dr Sullivan, Dr Vaughn, and Dr Jaffee have disclosed no relevant financial relationships.

American Academy of Neurology 2017 Annual Meeting (AAN). Abstract S14.006. Presented April 24, 2017.

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