Mortality during 25 years of follow-up of a cohort with diabetes

Abstract

Background: Diabetes is one of the most common chronic diseases in Western populations. There have been few large published cohort studies of people with diabetes that have had more than 10 years of follow-up, and none other than the present one are in the UK. Such studies are important to understand the long-term fatal consequences of diabetes and their variation over time and between countries.

Methods: Cause-specific mortality was analysed in follow-up from 1966-1970 to December 1992 of 5783 members of the British Diabetic Association living in England and Wales during 1966-1970. Comparison was made with age-, sex- and calendar year-specific mortality by cause in the general population of England and Wales.

Results: During the follow-up 3399 (58.8%) subjects died. The relative risk of all-cause mortality in the cohort compared to the general population was 2.31 in women and 1.58 in men (both P < 0.001).Relative risks were greater for women than men at almost all ages and for each major diabetes-related cause of death. Absolute excess ('attributable') mortality rates were also greater in women than in men, except at ages < 50. Half the deaths in each sex were from circulatory diseases and only 3.4% were from renal disease. The relative risks of mortality for all-causes and circulatory diseases were particularly great at younger ages, but changed little with duration of follow-up. At ages < 40 the relative risks for all-causes were 3.75 in men and 5.51 in women and for ischaemic heart disease were 10.44 and 25.25 respectively (all P < 0.001). At these ages one-third of deaths were due to acute complications of diabetes, suicides and accidents, whereas at older ages these accounted for only 4% of deaths.

Conclusions: The mortality rates at young ages in the cohort were around twice those in Sweden, Norway and Israel, suggesting that many of the deaths in England and Wales are preventable. The results also indicate a particular need for investigation and amelioration of cardiovascular risk factors in English and Welsh patients, especially women.