B-Mode Ultrasound Grading of Cryptogenic Steatotic Liver Disease and Association with the Level of Sun Exposure in Zaria, Nigeria: A Case-Control Study.

Background: Cryptogenic Steatotic Liver Disease (CSLD) is a novel subject where the liver has significant steatosis but without a known cause or abnormal cardiometabolic risk factors. Its aetiology and associations with sunlight exposure remain underexplored, particularly in Nigeria. CSLD is a growing public health concern in Nigeria, characterized by its potential progression to severe liver complications such as cirrhosis and liver cancer, posing significant health risks. This study aimed to determine the association between CSLD and the level of sun exposure.

Methodology: This case-control study involved 181 healthy subjects with CSLD and an equal number of normal subjects without CSLD as controls. This made for a total number of 362 subjects. They were recruited into the study consecutively as they emerged after clinical, laboratory, and imaging screenings. A liver ultrasound scan was done using a 3.5MHz frequency transducer to screen for the steatotic liver. The severity of liver steatosis was evaluated by ultrasound bright liver scores (BLS). A daily sun exposure score based on our local pattern was calculated using the information from the administered questionnaire. The data were analyzed with GraphPad Prism software version 6.

Results: the median (IQR) age of CSLD and control groups were 44.0 (28.5 - 54.0) and 44.0 (30.0 - 55.0) years. Wilcoxon matched pairs signed rank comparison test showed no significant difference in the ages of the two study groups (p = 0.5578), indicating age matching of the study participants. There was a significant association (χ² = 59.03, df = 18, p< 0.0001) between age and development of CSLD. One hundred and eighty-one study subjects with CSLD comprised 83 (45.8%) males and 98 (54.1%) females.The median (IQR) values of the control group's sun exposure score differed significantly from those of the CSLD groups (p = 0.0001) for all categories (mild, moderate, severe steatosis). A multivariate logistic regression analysis model, weighted by years of age and sex, revealed that low sunlight exposure is a significant independent risk factor.

Conclusion: The study shows that limited sun exposure is significantly associated with developing CSLD among Nigerians in Zaria. There is also a significant independent risk factor.