Constant noise isn't just annoying -- it might actually hurt our health beyond hearing loss, according to a new review published in The Lancet.
A team of researchers from the U.S. and Europe analyzed published literature on the effects of noise on health, and found associations between noise and heart disease, cognitive performance, sleep problems and hospital patient outcomes. This is all in addition to the more obvious deleterious effects of noise on our hearing abilities.
Take sleep, for instance. When we're sleeping, our auditory system is still awake and capable of recognizing outside events, study researcher Mathias Basner, M.D., Ph.D., M.Sc., an assistant professor of sleep and chronobiology in psychiatry at the University of Pennsylvania School of Medicine, explained to HuffPost. Noise negatively affects sleep quality similarly to a sleep condition like sleep apnea -- where brief pauses in breathing through the night lead to disturbed sleep -- because noise can wake people up several times throughout the night without them even realizing it.
"You're briefly waking up throughout the night, and it doesn't even have to be consciously," he said.
In addition, chronic noise exposure can lead to increases in blood pressure and excretion of stress hormones. "If that happens over years and years and years, that could actually contribute to cardiovascular health outcomes, stroke and so on," Basner said.
Researchers also mentioned in the review that noise could affect health by increasing stress levels and blood pressure levels, which can therefore take a toll on heart health. Noise exposure could also have an impact on mental functioning of children by prompting "communication difficulties, impaired attention, increased arousal, learned helplessness, frustration, noise annoyance, and consequences of sleep disturbance on performance," they wrote in the review.
Hospital noise from machines, conversations and pagers -- particularly in intensive care units -- has also been linked in research to worsened patient outcomes through increased cardiovascular stress and longer healing times, among other factors. The researchers noted in the review that health care providers could also be negatively affected by noise:
Evidence of negative effects of noise on hospital staff is increasing, particularly for nurses, with noise-induced stress linked to burnout, diminished well-being, and reduced work performance. Substantial proportions of staff report annoyance, irritation, fatigue, and tension headaches, which they assign to the noisy workplace environment. Noise also affects speech intelligibility and could therefore lead to misunderstandings that result in medical errors.
Basner pointed out that the studies included in the review were either cross-sectional -- which is not considered a strong type of study design -- or retrospective -- which are based on memory, and thus subject to human recall error. A robust, prospective study is needed to fully examine the associations between noise and health, he said, and because no such research exists yet, it's hard to say what maximum levels of noise exposure are considered safe.
Of course, noise is not singular -- it often happens in tandem with other potentially unhealthy factors. So what's the point where noise from traffic causes a health issue, versus the air pollution that comes from car emissions? And what about the possibility that people who live closer to highways might also be of a lower socioeconomic status than those who can afford to live in gated areas far away from major roads, and it's the socioeconomic factors that actually hurt health? "That is always a big problem in these studies," Basner noted. "Epidemiologists call them confounding factors -- a noisy area will have more pollutants, so noise is related to air pollutants: It's hard to tease them apart."
But still, he said, other studies have taken into account these other variables and adjusted for them in statistical models, so the review still identifies a clear association between noise in particular and health.
And while it's impossible to steer clear of noise altogether, Basner says that avoiding it and contributing less to noise levels are good strategies to take. For instance, if your house faces a noisy roadway, sleep in the back part of the home that's further away from the road, he suggested. He also recommended using noise-canceling headphones to limit noise exposure to your ears.