You've heard it plenty of times before: Adults should spend at least seven to nine hours sleeping each night, per the recommendation of the National Sleep Foundation. But does it matter when you finally call it a day and decide to head to bed? As long as you're getting a full night's sleep, who cares what time you choose to hit the hay, right? Not necessarily, according to research. NBC News and ABC News analyzed two different studies that showed a correlation between bedtime, heart health and mood swings.
How a Late Bedtime May Affect Your Heart
The study, presented at the American College of Cardiology's 58th annual Scientific Session in Orlando, analyzed men who went to sleep before midnight, in comparison to those who laid down to rest after 12 a.m. These men were younger than 61 and shared information on blood pressure, cholesterol, weight, BMI and waist circumference. They also had their arteries examined and completed a questionnaire that went over sleep patterns, such as duration and bedtime.
The men who went to bed after midnight showed more signs of arterial stiffening, which is an early symptom of heart disease – even if they slept the recommended seven to nine hours.
Dr. Daniel Jones, former president of the American Heart Association, told ABC News that while these individuals were prioritizing duration of sleep, their average bedtime was the poor sleeping habit that could be to blame.
"There are a lot of potential reasons for this causal link, [such as] some of the chemicals or hormones in our body that are tied to sleep," Jones said. "People with less deep sleep and less duration of sleep have more adrenaline release, and it's likely that some of those hormones or chemicals could be related to the poor health of those with less healthy sleep habits."
This holds especially true if you consider the distractions one may have from sleeping through the early morning hours. While heading to sleep at midnight and waking up at 8 a.m. means you got a full night's sleep, your rest may have been disturbed by other family members waking up earlier, bustling traffic and other distracting noises one tends to hear in the morning when most people are getting ready for work and school.
Going to Sleep to Late May Impact Your Mood
Another study shows a significant correlation between bedtime and mood. Lead researcher Dr. Maria Paz Loayza Hidalgo of the Universidade Federal do Rio Grande do Sul in Porto Alegre selected 200 people in good health with no signs of mental illness and asked them to talk about their sleep habits and express any feelings of depression. After the assessment, the researchers found that those who went to sleep later in the evening – commonly referred to as "night owls" – were three times more likely to experience depressive symptoms than those who had earlier bedtimes. What's alarming is that those who experienced less depressive symptoms were only heading to bed about an hour earlier than night owls.
The takeaway from this study, according to Dr. Ian Cook, associate professor of psychiatry at the University of California, Los Angeles and the director of Depression Research & Clinic Program at the university, is that even the smallest changes to your sleeping habits can alleviate mood swings and depressive symptoms.
"The study shows that even relatively subtle shifts in patterns of sleep seem to make a big difference in how people rate their mood," he told NBC News. "That's very intriguing stuff. Like any good study, it raises many more questions than it answers."
The Early Bird Gets the Worm
At the end of the day, one thing still remains true: A good night's sleep of seven to nine hours each night is critical. If you're experiencing heart issues or mood swings, shifting your bedtime, even subtly, may help alleviate such problems. Consider this advice to lead an overall healthier lifestyle.