An investigation of the population impact of variation in HbA1c levels in older people in England and Wales: from a population based multi-centre longitudinal study

Abstract

Background: Diabetes is common in the older population and is increasing. Glycated hemoglobin (HbA1c) is an indicator of average blood glucose concentration over the past three months. The HbA1c test is currently one of clinical methods used to check diabetes control. Recent studies have suggested diabetes is a risk factor for dementia, cognitive dysfunction and physical disability. In addition, there have reported the relationship between HbA1c and mortality on all cause, cardiovascular disease and cognitive function, but few studies have investigated the relationship concentrating on the older population. The aim of this study is to investigate the association between the level of HbA1c and mortality from all causes, incident cardiovascular disease, cognitive decline and physical disability in people aged 65 and over in England and Wales.

Methods: 1139 men and women aged 69 years and over who were participants in a ten year population based ageing multi-centre, longitudinal study who had HbA1c measurements after 5-6 years of follow up. All participants were flagged for death notification including causes at the Office of National Statistics. Information on health including vascular conditions, cognitive status, physical function and dementia were available from the study both before and after the HbA1c measurement. Survival analyses and logistic regression were conducted.

Results: Mortality from all causes, cardiovascular and ischaemic heart disease increased with increasing HbA1c. Participants with diagnosed diabetes or who had HbA1c > or = 7% but no self-reported diabetes had increased mortality risk from all causes and cardiovascular diseases. The respondents in the group HbA1c > or = 7% who had not been diagnosed with diabetes had a significantly higher risk (odds ratio = 4.8 95% CI: 1.1 to 21.6) of developing dementia. Individuals who had self-reported diabetes but a HbA1c level < 7% had mortality and dementia incidence comparable to individuals without diabetes and HbA1c < 7%.

Conclusion: The findings support previous reports that bio-markers of glucose metabolism are associated with long term outcomes, such as mortality and dementia.

Figure 1

MRC CFAS, flow diagram of study.

Figure 2

All-cause mortality by five categories of respondents.