Introduction In Taiwan, outpatients’ average travel distance (TD) is 17.68 km, and workers’ TD and travel time (TT) for outpatient services are only 8.2 km and 27.6 mins. Poor medical accessibility of occupational outpatient service can also lead to under-reporting of occupational diseases (ODs).

Methods In Taiwan, Network of Occupational Diseases and Injuries Service (NODIS), composed of 9 major reporting hospitals, is an important surveillance system of ODs. Using NODIS’s reporting data and manpower survey from 2008 to 2018, we calculate each town’s incidence rate of occupation diseases (IROD) and expected IROD according to workers’ occupations and job titles, and each town’s shortest TD and TT to 9 major reporting hospitals is estimated by Google Maps’ Distance Matrix API. Quasi-Poisson regression model is employed to investigate effect of TD and TT on IROD.

Results There are 8017 cases of suspected ODs in NODIS from 2008 to 2018, and 3306 cases are confirmed as definite ODs. Adjusted by workers’ occupations and job titles, as TD/TT increases by 10 km/10 mins, IROD significantly decreases by 10.90%/10.74%, and less-disabled workers who have never stopped working or lost their jobs are more impeded by long TD and TT.Compared with towns with TD 45 km and offshore towns decreases by 38.93%, 39.58%, 50.03%, 55.01%, 65.71%, and 84.10%, and IRODs of towns with TT 10–15, 15–25, 25–35, 35–45, >45 mins and offshore towns decreases by 30.94%, 43.57%, 47.41%, 47.70%, 67.81%, and 85.29%. Around 40% ODs are under-reported due to poor medical accessibility.

Conclusion Our study shows how poor medical accessibility leads to serious under-reporting, and up to 40% ODs could be under-reported. Using this method, we can identify areas with poor medical accessibility and evaluate cost-effectiveness of adding reporting hospital.