Declining Incidence of Systemic Lupus Erythematosus in Norway 1999-2017: Data From a Population Cohort Identified by International Classification of Diseases, 10th Revision Code and Verified by Classification

OBJECTIVE

The goal of this study was to provide complete, robust data on annual systemic lupus erythematosus (SLE) incidence rates over nearly two decades from the Southeast Norway area (2.9 million inhabitants) and assess accuracy of SLE-specific International Classification of Diseases (ICD) codes for SLE diagnosis.

METHODS

From administrative databases, we identified all cases International Statistical Classification of Diseases and Related Health Problems, Tenth Revision (ICD-10) coded as SLE during 1999 through 2017 in Southeast Norway. We manually reviewed the chart of every case ICD-10 coded as SLE to either confirm or reject SLE diagnosis. Using SLE classification criteria, we classified all cases with confirmed SLE. We estimated annual incidence rates of classified SLE, and subsets, defined by age at diagnosis, sex, and parental country of birth. The chi-square test was applied for linear time-trend analyses of incidence.

RESULTS

Among the 3,488 cases ICD-10 coded as SLE, chart reviews confirmed SLE diagnosis in 1,558 (45%), of which 797 had new-onset disease during 1999 through 2017. Annual SLE incidence rates fell during 1999 to 2017. The fall was most pronounced in female persons 50 to 59 years old at diagnosis, in whom incidence fell from 3.4 to 1.1 per 100,000 persons (P trend < 0.001). Concurrent ecological data from the study area showed a 74% reduction in prescriptions of menopausal hormone treatment. Accuracy of ICD-10 codes for incident SLE diagnosis was acceptable in juveniles and young adults (up to 20 years) but otherwise low.

CONCLUSION

In a presumably complete population-based cohort, we identified decreasing incidence of SLE, especially among female persons 50 to 59 years old. Although reasons for declining incidence are not clear, ecological data indicate a possible role of environmental factors, for example, menopausal hormone treatments.

The role of alcohol use and cigarette smoking in sickness absence: Are there social inequalities?

BACKGROUND

While studies have found a social gradient in negative consequences of drinking and smoking, evidence is less clear for a gradient also in alcohol use and smoking's association with sickness absence. We investigate the association between alcohol use and cigarette smoking and general sickness absence, and examine the moderating role of socio-economic status for these associations when controlling for general health status.

METHOD

Questions on alcohol use, measured by the Alcohol Use Disorders Identification Test (AUDIT-C), smoking, general health and sickness absence were included in annual national cross-sectional telephone surveys on alcohol, tobacco and drug use (2015-18) amongst Norwegian adults aged 16-79-years (average response rate=59%). The analytic sample comprised 4719 full- and part-time employees aged 25-79 years (46.7% were female, mean age=44.3 years). Individual-level data on education were obtained from national registries.

RESULTS

In adjusted negative binomial regression analyses, current and former daily smoking were associated with a higher occurrence of sickness absence in groups with low educational attainment, but not in groups with high educational attainment. Alcohol use was negatively associated with sickness absence. While a significantly higher number of sickness days was reported by smokers in the low compared with the high education group, educational attainment did not moderate the alcohol use - sickness absence association.

CONCLUSION

Daily smoking is associated with sickness absence. A negative social gradient was found in the smoking - absence association. Reduced daily smoking might give a reduction in sickness absence.