Inequalities in cancer mortality trends in people with type 2 diabetes: 20 year population-based study in England

Abstract

Aims/hypothesis: The aim of this study was to describe the long-term trends in cancer mortality rates in people with type 2 diabetes based on subgroups defined by sociodemographic characteristics and risk factors.

Methods: We defined a cohort of individuals aged ≥35 years who had newly diagnosed type 2 diabetes in the Clinical Practice Research Datalink between 1 January 1998 and 30 November 2018. We assessed trends in all-cause, all-cancer and cancer-specific mortality rates by age, gender, ethnicity, socioeconomic status, obesity and smoking status. We used Poisson regression to calculate age- and calendar year-specific mortality rates and Joinpoint regression to assess trends for each outcome. We estimated standardised mortality ratios comparing mortality rates in people with type 2 diabetes with those in the general population.

Results: Among 137,804 individuals, during a median follow-up of 8.4 years, all-cause mortality rates decreased at all ages between 1998 and 2018; cancer mortality rates also decreased for 55- and 65-year-olds but increased for 75- and 85-year-olds, with average annual percentage changes (AAPCs) of -1.4% (95% CI -1.5, -1.3), -0.2% (-0.3, -0.1), 1.2% (0.8, 1.6) and 1.6% (1.5, 1.7), respectively. Higher AAPCs were observed in women than men (1.5% vs 0.5%), in the least deprived than the most deprived (1.5% vs 1.0%) and in people with morbid obesity than those with normal body weight (5.8% vs 0.7%), although all these stratified subgroups showed upward trends in cancer mortality rates. Increasing cancer mortality rates were also observed in people of White ethnicity and former/current smokers, but downward trends were observed in other ethnic groups and non-smokers. These results have led to persistent inequalities by gender and deprivation but widening disparities by smoking status. Constant upward trends in mortality rates were also observed for pancreatic, liver and lung cancer at all ages, colorectal cancer at most ages, breast cancer at younger ages, and prostate and endometrial cancer at older ages. Compared with the general population, people with type 2 diabetes had a more than 1.5-fold increased risk of colorectal, pancreatic, liver and endometrial cancer mortality during the whole study period.

Conclusions/interpretation: In contrast to the declines in all-cause mortality rates at all ages, the cancer burden has increased in older people with type 2 diabetes, especially for colorectal, pancreatic, liver and endometrial cancer. Tailored cancer prevention and early detection strategies are needed to address persistent inequalities in the older population, the most deprived and smokers.

Keywords: Cancer; Electronic health records; Inequalities; Mortality trends; Type 2 diabetes.

Fig. 1

Trends in all-cause mortality rates (a–f) and all-cancer mortality rates (g–l) (per 1000 person-years). Age-specific mortality rates for all-cause mortality (a) and all-cancer mortality (g). All rates were estimated for the median diabetes duration at the end of follow-up (8.4 years). Rates stratified by gender (b, h), ethnicity (c, i), socioeconomic status (d, j), BMI (e, k) and smoking status (f, l) were also age-adjusted and are presented for the median age at the end of follow-up (72 years). Error bars indicate 95% CIs. The number of all-cancer deaths in people of ethnicities other than White was small in some years, leading to predicted rates with large uncertainties. All estimates are also reported in ESM Tables 1–6

Fig. 2

Proportions of cancer deaths out of all-cause deaths by age (a–d), gender (e, f), ethnicity (g), deprivation (h, i), BMI (j–m) and smoking status (n–p). Proportions were calculated as the all-cancer mortality rate divided by the all-cause mortality rate in each stratum and calendar year. Error bars indicate 95% CIs, which were estimated using the non-parametric bootstrap method with 500 replicates. The number of all-cancer deaths in people of ethnicities other than White was small in some years, leading to predicted rates with large uncertainties and unstable proportion estimates; only the proportions for White ethnicity are shown (g). All estimates are also reported in ESM Tables 1–6

Fig. 3

Trends in cancer-specific mortality rates (per 100,000 person-years) for four common cancers: (a–e) breast cancer, (f–j) prostate cancer, (k–p) lung cancer and (q–v) colorectal cancer. Age-specific mortality rates for breast (a), prostate (f), lung (k) and colorectal (q) cancer. All rates were estimated for the median diabetes duration at the end of follow-up (8.4 years). Rates stratified by gender (l, r), ethnicity (b, g, m, s), socioeconomic status (c, h, n, t), BMI (d, i, o, u) and smoking status (e, j, p, v) were also age-adjusted and are presented for the median age at the end of follow-up (72 years). Error bars indicate 95% CIs. Stratified analysis by gender is not applicable for breast and prostate cancer. The number of breast and prostate cancer deaths in people of ethnicities other than White was small in some years, leading to predicted rates with large uncertainties

Fig. 4

Trends in cancer-specific mortality rates for type 2 diabetes-related cancers (per 100,000 person-years). Age-specific mortality rates for pancreatic (a) and liver (g) cancer. All rates were estimated for the median diabetes duration at the end of follow-up (8.4 years). Rates stratified by gender (b, h), ethnicity (c, i), socioeconomic status (d, j), BMI (e, k) and smoking status (f, l) were also age-adjusted and are presented for the median age at the end of follow-up (72 years). Error bars indicate 95% CIs. The numbers of liver cancer deaths in people of ethnicities other than White and in the most deprived group were small in some years, leading to predicted rates with large uncertainties. Because of a small number of events, trends for gallbladder and endometrial cancer mortality rates are not shown but estimates are reported in ESM Table 8