A population-based cohort study published in The Journal of the American Geriatrics Society (2016) tried to investigate whether low glycosylated hemoglobin (HbA1c), blood pressure (BP), and total cholesterol (TC) result into a lower mortality risk in older people with type 2 diabetes.
Cardiovascular disease (CVD) is a major cause of mortality in people with diabetes, a disease highly prevalent in older people. Although diabetes patients are encouraged to lower their blood glucose, blood pressure (BP), and total cholesterol (TC) to reduce the risk of CVD, the relationship between mortality and CVD risk factors has not been investigated for very old adults yet. The purpose of a new study was to determine whether lowering the CVD risk factors HbA1c, BP and TC can lower the mortality risk in very old adults with type 2 diabetes.
A baseline period of 12 months was selected for assessing participants’ records for smoking, body mass index (BMI), HbA1c, BP, and TC and baseline characteristics of the study cohort were described. Mortality was calculated by performing time-to-event analyses from the end of the baseline period of 12 months to either participants’ death or date of transfer out of the practice, or December 31, 2013. Associations between HbA1c, BP, and TC and mortality were evaluated with Cox proportional hazards models while adjusting the analyses for sex, age, duration of diabetes, smoking status, BMI, comorbidities, prescription of antidiabetic and cardiovascular drugs.
The participants who died in the ﬁrst 6 months of follow-up were excluded from the analysis and the main analysis was repeated to identify high-risk categories of HbA1c, BP, and TC for all-cause mortality. The total number of study participants was 25,966, with 53% women and there were 4,490 deaths in the follow-up period.
Overall, a U-shaped relationship was found between HbA1c and mortality and a reverse J-shaped relationship was observed between BP and mortality, while the trend of mortality decreased with the baseline TC increase. The same relationships between HbA1c, BP, and TC and mortality were observed when the analysis was repeated with excluding participants who died in the ﬁrst 6 months of follow-up. The mortality rate was 111.5, 80.5 and 87.7 per 1,000 person-years in participants with the reference HbA1c, BP and TC categories, respectively. By performing the analysis with the lowest risk categories as reference, high-risk categories for mortality were found to be: HbA1c less than 6.0%, BP less than 135/75 mmHg, and TC <3.0 mmol/L for men and <4.5 mmol/L for women.
The study results – consistent with the previous observational studies – showed that low HbA1c, BP, and TC might actually lead to higher mortality in very old adults with type 2 diabetes. Hence, additional work needs to be done to identify optimal values of HbA1c, BP, and TC to lower the mortality risk in very old type 2 diabetes patients.
The strength of this study was the inclusion of a large sample since it is difficult to include very old people in clinical trials because of safety reasons. The limitations of this study were the possible fluctuation of HbA1c, BP, and TC variables over time, lack of information on cause of death, and dependency on completeness and accuracy of CPRD records.
Written By: Hummara Aslam, MSc