An ecological study from several countries suggested that theprevalence of obesity and type 2 diabetes mellitus (T2DM) has been associated with an increase in nonalcoholic fatty liver disease (NAFLD) over the past two decades.

a. To address this finding, the association between T2DM and NAFLD was measured in 1,000,000 men and women who had baseline data on prevalence of diabetes and were followed for 20 years to measured who developed NAFLD. The risk ratio in this study was 3.0 for NALFD among those with T2DM compared to those without T2DM. What study design did they use in this study?Explain how the study was designed to obtain these results. (2.5 points).

b. In a second study, another team of investigators conducted a study to measure the strength of the association. They identified 3 large hospitals to recruit 200 patients with NAFLD and recorded prevalence of T2DM in these patients. They also identified 200 patients in the hospital who did not have NAFLD and were in the hospital for treatment of bone fractures. Prevalence of T2DM was also recorded in these patients. They reported a 4-fold higher risk of NAFLD in patients with a history of T2DM compared to those without T2DM.

What study design did they use in this study? Explain how the study was designed to obtain these results. (2.5 points).