You donât have to live under a flight path or next to a nightclub to be bothered by noise. Surprisingly low levels of noise â above 55 decibels (the equivalent of light traffic or an air conditioner) â especially at night is not only annoying but detrimental to health. Noise pollution is, warns the World Health Organization, a growing hazard, second only to air pollution in its ill effects. It is obviously linked to sleep disturbance but also to heart attacks, tinnitus, strokes and even obesity.
Noise has also been associated with increases in premature births and miscarriages, and this week its ill effects were extended to reducing male fertility. A study, in the international journal Environmental Pollution, of 206,492 men in South Korea found that being exposed to noise levels of more than 55 decibels for four years, especially at night, was associated with an increase in fertility problems. When the authors of the study compared postcodes and the noise associated with them to fertility (as measured by the quality of semen samples) they found an increase in infertility for each 10 decibels of noise above 55 decibels. The researchers tried to factor in other things that affect fertility, such as age, exercise, smoking, drinking, blood sugar, weight and medical history. But the design of the study meant they couldnât collect information on genetic factors or exposure to other things, such as chemicals that could also reduce fertility.
The research reinforces previous studies showing that listening to constant noise, even at a low level, can activate the bodyâs stress response, disrupting the normal control of sex hormones. Cortisol, released when you are irritated by constant noise, produces hormones which work in a feedback loop to lower levels of testosterone. This can reduce both the number of sperm and their mobility. Another study of men working in noisy conditions (119 decibels, which is louder than a police siren) also found lower testosterone levels and fewer, less mobile sperm.
But fertility problems have many causes, and the studies so far have limitations â and can only hint at an association. Any effect is likely to be very small. A study four years ago, linking aircraft noise with strokes and heart problems, caused concern but, as with this latest study, it could not rule out other factors that increase risk. Yet there is a plausible mechanism for the effects of noise on our health: noise triggers our stress pathway, and the link between levels of more than 55 decibels and a rise in blood pressure is one of the more solid associations.
How can you have less noise? You can try earplugs, heavy curtains or triple glaze your bedroom windows.