Purpose <p>The influence of lifestyle factors on the incidences of sudden sensorineural hearing loss (SSNHL) and Meniere’s disease (MD) is unclear. This study aimed to evaluate the association of modifiable lifestyle factors with the incidences of SSNHL and MD.</p> Methods <p>This nested case-control study used data from the National Database of Health Insurance Claims and Specific Health Checkups of Japan. The cases were those who developed SSNHL or MD within 12 months of a specific health checkup, whereas the controls were those who did not develop SSNHL or MD. The population was matched for sex, age, blood pressure, blood glucose level, and duration of follow-up at a case-to-control ratio of 1:10. To impute missing values, multiple imputations by chained equations were performed, and conditional logistic analysis was applied.</p> Results <p>Among the 14,768,613 who did not have SSNHL or MD in the previous 24 months, 28,753 and 45,072 developed SSNHL and MD, respectively. The odds ratio was 0.72 (95% confidence interval [CI]: 0.70, 0.75) for SSNHL and 0.70 (95% CI: 0.68, 0.73) for MD among current smokers, with non-smokers as reference. Poor sleep was associated with increased SSNHL and MD incidences. Meanwhile, having walking habits and higher alcohol consumption were associated with lower MD incidence.</p> Conclusion <p>This study found associations between modifiable lifestyle habits and the incidences of SSNHL and MD, but the results are inconclusive owing to study limitations. Further research is needed to validate the associations.</p>