All-cause mortality trends in a large population-based cohort with long-standing childhood-onset type 1 diabetes: the Allegheny County type 1 diabetes registry

Abstract

Objective: Although management of type 1 diabetes improved dramatically in the 1980s, the effect on mortality is not clear.

Research design and methods: We report trends in 30-year mortality using the Allegheny County (Pennsylvania) childhood-onset (age <18 years) type 1 diabetes registry (n = 1,075) with diagnosis from 1965-1979, by dividing the cohort into three diagnosis year cohorts (1965-1969, 1970-1974, and 1975-1979). Local (Allegheny County) mortality data were used to calculate standardized mortality ratios (SMRs).

Results: As of 1 January 2008, vital status was ascertained for 97.0% of participants (n = 1,043) when mean age ± SD and duration of diabetes were 42.8 ± 8.0 and 32.0 ± 7.6 years, respectively. The 279 deaths (26.0%) observed were 7 times higher than expected (SMR 6.9 [95% CI 6.1-7.7]). An improving trend in SMR was seen by diagnosis cohort at 30 years of diabetes duration (9.3 [7.2-11.3], 7.5 [5.8-9.2], and 5.6 [4.0-7.2] for 1965-1969, 1970-1974, and 1975-1979, respectively). Although no sex difference in survival was observed (P = 0.27), female diabetic patients were 13 times more likely to die than age-matched women in the general population (SMR 13.2 [10.7-15.7]), much higher than the SMR for men (5.0 [4.0-6.0]). Conversely, whereas 30-year survival was significantly lower in African Americans than in Caucasians (57.2 vs. 82.7%, respectively; P < 0.001), no differences in SMR were seen by race.

Conclusions: Although survival has clearly improved, those with diabetes diagnosed most recently (1975-1979) still had a mortality rate 5.6 times higher than that seen in the general population, revealing a continuing need for improvements in treatment and care, particularly for women and African Americans with type 1 diabetes.

Figure 1

Life-table analyses by sex (A), race (B), diagnosis cohort (C), and age at onset (D) for individuals with type 1 diabetes between 1965 and 1979 in the Allegheny County type 1 diabetes registry cohort. P values calculated using the log-rank test. C: 1965–1969 vs. 1970–1974, P = 0.02, and 1965–1969 vs. 1975–1979, P = 0.02. D: <10 vs. 10–14 years, P = 0.002, and <10 vs. >14 years, P < 0.001.

Figure 2

SMRs and 95% CIs for the overall (A) Allegheny County Type 1 Diabetes Registry cohort and by sex (B), race (C), and diagnosis cohort (D) at 5-year intervals of follow-up. C and D are spaced around the 5-year intervals for visual clarity; however, all SMRs are calculated at the same 5-year follow-up points.