Thyroid eye disease in New Zealand: interaction between ethnicity and smoking status

This study was conducted to describe the epidemiology of thyroid eye disease (TED) in New Zealand.

One hundred and sixty-one subjects with TED seen over a 14-year period in Auckland, from a combined ophthalmology-endocrinology clinic, had data extracted from clinical notes.

Median age at onset was 47.0±15.1 years and 77.6% were female. Crude yearly incidence of TED (per 1,000,000) was 12.6 in non-smokers and 67.3 in smokers (p<0.001).  On univariate analysis, female gender, Māori ethnicity and smoking were associated with incidence of TED. On multivariate analysis, female gender and smoking status were associated with risk of TED, and the difference in ethnicity was explained by smoking status. Māori subjects with TED were more likely to be current smokers (72.7%) compared to European (39.2%), Pacific Peoples (33.3%), Asian (8.3%) and Other (12.5%). Māori ethnicity and current smokers were associated with a higher clinical activity score at presentation (p=0.049 and p=0.027).

A strong association was demonstrated with female gender and smoking status and rate of TED. Māori have increased rates of TED; however, this difference was explained by smoking. Eliminating smoking would result in at least a 28.1% reduction in TED incidence in New Zealand.