Association of fatty liver index with risk of incident type 2 diabetes by metabolic syndrome status in an Eastern Finland male cohort: a prospective study

OBJECTIVE: Fatty liver disease (FLD) is increasingly recognised as a predictor of cardiometabolic risk. Our objective was to examine if metabolic syndrome (MS) status affects the association of FLD with incident type 2 diabetes (T2D) in middle-aged men. DESIGN: Prospective epidemiological study. SETTING: University affiliated research centre in Kuopio, Eastern Finland. PARTICIPANTS: Our subjects were 1792 Finnish men without diabetes at baseline in the KuopioIschaemicHeart Disease Risk Factor Study cohort. OUTCOME MEASURE: Using fatty liver index (FLI), the association of baseline FLD with incident T2D was analysed in multivariable-adjusted Cox regression models, considering their MS statuses. The main models were adjusted for constitutional factors, lifestyle factors, biomarkers of inflammation and for high (FLI ≥60) versus low (FLI <30) FLI categories. RESULTS: During a mean follow-up of 19 years, 375 incident cases of T2D were recorded. In the full model, the HR (HR (95% CI)) for T2D was 3.68 (2.80 to 4.82). The association was attenuated, but maintained, with further adjustment for metabolic factors. When MS status was adjusted for in place of metabolic factors, the HRs (95% CIs) were 2.63 (1.92 to 3.59) for FLI ≥60 and 1.77 (1.35 to 2.31) for MS. In MS-stratified analysis, FLI predicted T2D only among persons without MS. In unstratified analysis with subjects categorised by FLI-MS, persons with FLI ≥60 without MS had increased risk for T2D (HR=3.19 (2.26 to 4.52)) compared with persons with FLI <30 without MS. Persons with FLI <30 and MS had greater risk (HR=4.31 (2.15 to 8.61)) and persons with both FLI ≥60 and MS had the greatest risk (HR=4.66 (3.42 to 6.35)). CONCLUSION: Generally, FLD (FLI ≥60) predicts T2D. It specifically predicted T2D among men without MS but not among men with MS, for whom MS alone already increases the risk. Both FLI and MS can complement each other in screening and surveillance for persons with increased T2D risk.