A new Japanese study suggests that smoking increases the risk of hearing loss, in what the researchers believe is the largest to date, investigating the link between tobacco and a decline in hearing.

Carried out by Japan’s National Center for Global Health and Medicine, the large-scale study looked at 50,195 participants aged 20 to 64 years over an eight-year period.

All participants were free of hearing loss at the start of the study, with tests performed annually to identify any decline in hearing. The researchers also analyzed data from annual health checkups, and asked each participant to complete a health-related lifestyle questionnaire.

Participants were also asked about about their smoking status, and whether they were a current, former, or never smoker. Current smokers were also asked about the number of cigarettes smoked per day, while former smokers were asked how long ago they quit.

The results showed that, even after taking into account factors such as noise exposure at work, current smokers had a 1.2 increased risk of developing low-frequency hearing loss, and a 1.6 increased risk of high-frequency hearing loss, when compared with never smokers.

The risk of developing both high- and low-frequency hearing loss also increased with the number of cigarettes smoked per day.

Former smokers had a 1.2 increased risk of high-frequency hearing loss, although the risk of hearing loss appears to decrease within five years after quitting smoking.

“With a large sample size, long follow-up period, and objective assessment of hearing loss, our study provides strong evidence that smoking is an independent risk factor of hearing loss,” said the study’s lead author Dr. Huanhuan Hu of Japan’s National Center for Global Health and Medicine.

“These results provide strong evidence to support that smoking is a causal factor for hearing loss and emphasize the need for tobacco control to prevent or delay the development of hearing loss.”

The results can be found published online in the journal Nicotine & Tobacco Research. JB

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