PT  - JOURNAL ARTICLE
AU  - Rim, Tyler Hyungtaek
AU  - Kim, Dong Wook
AU  - Cheng, Ching-Yu
AU  - Kim, Sung Soo
TI  - Protective effect of smoking against pterygium development in men: a nationwide longitudinal cohort study in South Korea
AID  - 10.1136/bmjopen-2017-017014
DP  - 2017 Nov 01
TA  - BMJ Open
PG  - e017014
VI  - 7
IP  - 11
4099  - http://bmjopen.bmj.com/content/7/11/e017014.short
4100  - http://bmjopen.bmj.com/content/7/11/e017014.full
SO  - BMJ Open2017 Nov 01; 7
AB  - Objective The present study aimed to evaluate the association between smoking and incident pterygium in adult Korean men.Design A retrospective nationwide longitudinal cohort.Setting National Health Insurance database of South Korea.Participants This study included Korean men (age range: 40–79 years) registered in the Korea National Health Insurance Service database from 2002 through 2013. We compared HRs for pterygium between 90 547 current/past and 90 547 never-smokers via 1:1 propensity-matched analysis.Primary outcome measure Incident cases of pterygium were identified from the database.Results Pterygium developed in 5389 (6.0%) never-smokers and 3898 (4.3%) past/current smokers (P<0.001). The incidence of pterygium per 1000 person-years in never-smokers and in past/current smokers was 6.5 and 4.7, respectively (age-adjusted HR, 0.73; 95% CI, 0.70 to 0.76). This protective effect was more pronounced among current smokers than among past smokers (for current smokers: HR, 0.68; 95% CI, 0.65 to 0.71 and for past smokers: HR, 0.85; 95% CI, 0.80 to 0.90). A longer duration of smoking and higher amounts of cigarette consumption were associated with a lower incidence of pterygium.Conclusions Longitudinally, cigarette smoking was associated with a reduced risk of pterygium, and this protective effect was more pronounced among current smokers than among past smokers.