Insulin dependent diabetes mellitus : mortality and the association of dietary intake with early renal disease

Methods: Death certificate information from an 8 and a half year period was collected to determine mortality in an IDDM cohort relative to the Tasmanian population, and to determine the frequency of renal disease as a cause of death in IDDM. In 1991-93, a cross-sectional study of adults with IDDM who were resident in Tasmania on May 1st 1984 was carried out to determine the relationship of microalbuminuria with usual dietary protein intake and with usual saturated fat intake. Diet was assessed using a food frequency questionnaire (FFQ). Results: The all-cause standardised mortality ratio for people with IDDM was 7.7 for females and 3.0 for males. The major stated causes of death were cardiovascular disease (52% of females, 50% of males) and renal disease (17% of females, 12% of males). There was a positive relationship between energy adjusted saturated fat intake and previously unidentified microalbuminuria. The odds ratio for prevalence of microalbuminuria in the highest quintile of energy adjusted usual saturated fat intake compared to the others after adjustment for other factors was 4.9 (95% CI: 1.4-17.5). The positive relationship between energy-adjusted saturated fat intake and previously unidentified microalbuminuria was strengthened by adjusting for serum HDL cholesterol, age at diabetes diagnosis and energy-adjusted protein intake. Adjustment for gender, glycosylated haemoglobin, duration of diabetes and obesity had no substantial effect. There was a negative relationship between energy adjusted protein intake and previously unidentified microalbuminuria. The odds ratio for prevalence of microalbuminuria in the highest quintile of energy adjusted protein intake compared to the lower four after adjustment for other factors was 0.08 (95% CI: 0.004-0.6). The negative association between energy adjusted protein intake and previously unidentified microalbuminuria was strengthened by controlling for energy adjusted saturated fat intake, however gender, glycosylated haemoglobin, serum HDL cholesterol, obesity, duration of diabetes and age at diabetes diagnosis had no substantial effect. Conclusions: People with IDDM in Tasmania experience 4.6 times the mortality of the general population with renal disease being a significant contributor. The relative mortality rate is higher for females than for males. A high relative dietary intake of saturated fat may be a contributory cause of microalbuminuria and a high relative dietary intake of protein may be protective against the development of microalbuminuria. These preliminary findings should be confirmed using a prospective study design.