Association between diabetes and cause-specific mortality in rural and urban China

Abstract

Importance

In China diabetes prevalence has increased substantially in recent decades, but there are no reliable estimates of the excess mortality currently associated with diabetes.

Objective

To assess the proportional excess mortality associated with diabetes, and to estimate the diabetes-related absolute excess mortality in rural and urban China.

Design, setting, and participants

A 7-year nationwide prospective study of 512,869 adults aged 30-79 years from 10 (5 rural, 5 urban) localities across China, recruited from 6/2004 to 7/2008 and followed until 1/2014.

Exposure

Diabetes (previously diagnosed or screen-detected) recorded at baseline.

Main outcome measures

All-cause and cause-specific mortality, collected through established death registries. Cox regression was used to estimate adjusted mortality rate ratios (RRs) comparing those with versus without diabetes at baseline.

Results

Overall, the mean (SD) age was 51.5 (10.7) years, 59% (n=302,618) were women, and 5.9% (n=30,280) had diabetes (rural 4.1%, urban 8.1%, men 5.8%, women 6.1%, previously diagnosed 3.1%, screen-detected 2.8%). During 3.64 million person-years of follow-up, there were 24,909 deaths, including 3,384 among individuals with diabetes. Compared to adults without diabetes, individuals with diabetes had a significantly increased risk of all-cause mortality (1373 vs 646 deaths per 100,000; adjusted RR, 2.00 [95%CI, 1.93 to 2.08]), which was higher in rural than urban areas (rural RR, 2.17 [95%CI 2.07 to 2.29]; urban RR, 1.83 [95%CI, 1.73 to 1.94]). Presence of diabetes was associated with increased mortality from ischaemic heart disease (3287 deaths; RR, 2.40 [95%CI, 2.19 to 2.63]), stroke (4444 deaths; RR, 1.98 [95%CI, 1.81 to 2.17]), chronic liver disease (481 deaths; RR, 2.32 [95%CI, 1.76 to 3.06]), infections (425 deaths; RR, 2.29 [95%CI, 1.76 to 2.99]), and cancer of the liver (1325 deaths; RR, 1.54 [95%CI 1.28 to1.86]), pancreas (357 deaths; RR, 1.84 [95%CI, 1.35 to 2.51]), female breast (217 deaths; RR, 1.84 [95%CI, 1.24 to 2.74]), and female reproductive system (210 deaths; RR, 1.81 [95%CI, 1.20 to 2.74]). For chronic kidney disease (365 deaths), the RR was higher in rural than urban areas (18.69 [95%CI, 14.22 to 24.57] versus 6.83 [95%CI, 4.73 to 9.88]). Among those with diabetes, 10% of all deaths (rural 16%, urban 4%) were due to definite or probable diabetic ketoacidosis or coma (408 deaths).

Conclusions and relevance

Among adults in China, diabetes was associated with increased mortality from a range of cardiovascular and non-cardiovascular diseases. Although diabetes was more common in urban areas, it was associated with a greater excess mortality in rural areas.