Street noise outside a child's bedroom - studies on how much it affects the quality of sleep?

Question

Our 3 year old's bedroom is facing a street that has some low degree of traffic at night. There is a bus stop right under the window (we live on the 2nd floor), with buses going every 10 minutes until midnight and starting again around 5.30 am. Occasionally on Saturday nights some motorcycles would cause higher noise.

She moved to her own room about a year ago, and sleeps alone. We have never noticed that any of the car noise outside would disturb her sleep. We are nevertheless wondering if it can have any impact on the quality of her sleep in some ways that are not directly apparent. Does anyone know of any studies (on either children or adults) on this topic?

(Note: our own bedroom is on the opposite side of the apartment facing an inner garden, totally quiet. We cannot easily swap them because of their different sizes).

Answer 1

Night noise is linked to insomnia and lower sleep duration. This link is mostly supported by multiple research studies. This association was considered substantial enough for the World Health Organisation (WHO) to issue the night noise guidelines in 2009 (see below). I show 2 relevant research studies below, but one can quickly find multiple other research studies and reviews. A good starting point is searching for pubmed street noise sleep in your favorite search engine.

Caveats:

• Most studies with large sample sizes tend to be epidemiological, and it is possible that confounding factors other than noise contribute to the associations found.

• Large confidence intervals found in epidemiological studies suggest that noise sensitivity varies widely across people, so YMMV when applying these results to real life.

• Intervention studies on this subject tend to have fewer subjects, which may reduce the reproducibility.

SELECTED REFERENCES:

World Health Organisation (WHO). Night noise guidelines for Europe. Copenhagen, Denmark: World Health Organisation (WHO); 2009. http://www.euro.who.int/__data/assets/pdf_file/0017/43316/E92845.pdf

Considering the scientific evidence on the thresholds of night noise exposure indicated by L_{night,outside} as defined in the Environmental Noise Directive (2002/49/EC), an L_{night,outside} of 40 dB should be the target of the night noise guideline (NNG) to protect the public, including the most vulnerable groups such as children, the chronically ill and the elderly. L_{night,outside} value of 55 dB is recommended as an interim target for the countries where the NNG cannot be achieved in the short term for various reasons, and where policy-makers choose to adopt a stepwise approach. These guidelines are applicable to the Member States of the European Region, and may be considered as an extension to, as well as an update of, the previous WHO Guidelines for community noise (1999).

Jaana I. Halonen, Jussi Vahtera, Stephen Stansfeld, Tarja Yli-Tuomi, Paula Salo, Jaana Pentti, Mika Kivimäki, and Timo Lanki. Associations between Nighttime Traffic Noise and Sleep: The Finnish Public Sector Study. Environ Health Perspect. 2012 Oct; 120(10): 1391–1396. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3491945/

Methods: Noise levels of nighttime–outdoor traffic were modeled based on the traffic intensities in the cities of Helsinki and Vantaa, Finland. In these cities, 7,019 public sector employees (81% women) responded to postal surveys on sleep and health. We linked modeled outdoor noise levels to the residences of the employees who responded to the postal survey. We used logistic regression models to estimate associations of noise levels with subjectively assessed duration of sleep and symptoms of insomnia (i.e., difficulties falling asleep, waking up frequently during the night, waking up too early in the morning, nonrestorative sleep). We also used stratified models to investigate the possibility of vulnerable subgroups.

Results: For the total study population, exposure to levels of nighttime–outside (L_{night,outside}) traffic noise > 55 dB was associated with any insomnia symptom >= 2 nights per week [odds ratio (OR) = 1.32; 95% confidence interval (CI): 1.05, 1.65]. Among participants with higher trait anxiety scores, which we hypothesized were a proxy for noise sensitivity, the ORs for any insomnia symptom at exposures to L_{night,outside} traffic noises 50.1–55 dB and > 55 dB versus <= 45 dB were 1.34 (95% CI: 1.00, 1.80) and 1.61 (95% CI: 1.07, 2.42), respectively.

Kjell Vegard Weyde, Norun Hjertager Krog, Bente Oftedal, Jorunn Evandt, Per Magnus, Simon Øverland, Charlotte Clark, Stephen Stansfeld, and Gunn Marit Aasvang. Nocturnal Road Traffic Noise Exposure and Children’s Sleep Duration and Sleep Problems. Int J Environ Res Public Health. 2017 May; 14(5): 491. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5451942/

The present cross-sectional study used data from The Norwegian Mother and Child Cohort Study. Parental report of children’s sleep duration and sleep problems at age 7 was linked to modelled levels of residential night-time road traffic noise. The study population included 2665 children from Oslo, Norway. No association was found between road traffic noise and sleep duration in the total study population (odds ratio (OR): 1.05, 95% confidence interval (CI): [0.94, 1.17]), but a statistically significant association was observed in girls (OR: 1.21, 95% CI: [1.04, 1.41]). For sleep problems, the associations were similar (OR: 1.36, 95% CI: [0.85, 2.16]) in girls. The ORs are presented for an increase of 10 dB. The findings suggest there is an association between road traffic noise and sleep for girls, underlining the importance of protecting children against excessive noise levels.