Secular Decline in Mortality from Coronary Heart Disease in Adults with Diabetes Mellitus: Cohort Study

Objective: To examine trends in fatal coronary heart disease in adults with and without diabetes.

Design: Cohort study.

Setting: Two surveys of the Nord-Trøndelag health study (HUNT), a population based study in Norway.

Participants: 74 914 men and women from the first survey (1984-6) and 64 829 from the second survey (1995-7).

Main Outcome Measure: Age specific mortality from coronary heart disease among adults with and without diabetes during two consecutive nine year follow-up periods.

Results: A total of 2623 men and 1583 women died from coronary heart disease. Mortality rates were substantially lower during the most recent follow-up period: among men aged 70-79 without diabetes, deaths per 1000 person years declined from 16.38 to 8.79 (reduction 48%, 95% confidence interval 39% to 55%) and among women aged 70-79 from 6.84 to 2.68 (62%, 52% to 70%). Among the same age group with diabetes, deaths per 1000 person years in men declined from 38.97 to 17.89 (54%, 32% to 69%) and in women from 28.15 to 11.83 (59%, 37% to 73%). The reduction was more noticeable in age groups younger than 70 at baseline, and less pronounced among people aged 80 or more. Mortality from coronary heart disease was more than twofold higher in people with than without diabetes, with a slightly stronger association in women. The difference in mortality by diabetes status remained almost unchanged from the first to the second survey.

Conclusion: The strong general reduction in mortality rates from coronary heart disease from the first to the second follow-up period also benefited people with diabetes, but the more than twofold higher mortality from coronary heart disease associated with diabetes persisted over time.