Lecture 22 - Diabetes Epidemiology

what is the definition of diabetes mellitus

a metabolic disorder characterized by abnormally high levels of glucose in the blood = hyperglycemia

why does hyperglycemia occur

the body cannot produce enough insulin - pancreatic beta cell dysfunction or destruction

the body cannot use insulin properly - cells are unable to take in glucose and use it for energy

what are symptoms of hyperglycemia 

polyuria and polydispia 

headache 

fatigue 

blurred vision 

difficulty concentrating 

weight loss (especially type 1) 

what is associated with chronic hyperglycemia 

complications affecting the eyes, kidneys, nerves, increased risk of cardiovascular disease 

what is prediabetes

glucose levels are elevated but not above the diagnostic threshold for diabetes

• impaired fasting glucose (IFG)

• impaired glucose tolerance (IGT)

what does the presence of impaired fasting glucose or impaired glucose tolerance indicate

higher risk of developing diabetes

higher risk of microvascular complications

what is type 1 diabetes mellitus

primarily the result of pancreatic beta cell destruction and prone to ketoacidosis 

includes cases due to an autoimmune process

affects up to 10% of people with diabetes 

what is type 2 diabetes mellitus

caused by insulin resistance and/or a deficit in insulin secretion

most common form, affecting about 90% of people with diabetes

usually happens in adults, balance between insulin production and insulin resistance - glucose is elevated either due to insulin resistance or impaired release

what is gestational diabetes

glucose intolerance with onset or first recognition during pregnancy

second trimester oral glucose tolerance test to screen

what is the diagnostic criteria for diabetes 

fasting plasma glucose ≥ 7 mmol/L, or

A1c ≥ 6.5% (in adults, not for suspected type 1 diabetes), or

2hPG in a 75g OGTT ≥ 11.1 mmol/L, or

random BG ≥ 11.1

what is the diagnostic criteria for diabetes in the absence of symptomatic hyperglycemia

confirmatory laboratory test must be done on another day

preferably the same test repeated for confirmation 

what is the diagnostic criteria for prediabetes

fasting plasma glucose 6.1-6.9 mmol/L (impaired fasting glucose) or

2hPG in a 75g OGTT 7.8-11.0 mmol/L (impaired glucose tolerance) or

A1c 6.0-6.4% (prediabetes)

what is impaired fasting glucose

FPG 6.1-6.9 mmol/L

what is impaired glucose tolerance

2hPG in a 75G OGTT 7.8-11.0

what are the recommendations for screening for type 1 diabetes 

no recommendations to screen 

no universally available test 

no evidence to support interventions to prevent T1DM

what are the screening recommendations for type 2 diabetes

screen based on known risk factors for type 2 diabetes or presence of diabetes associated conditions (retinopathy, decreased kidney function, CV disease, dyslipidemia)

1 in 3 people with diabetes do not know it, usually begins 4-7 years before clinical diagnosis

what is the screening criteria for gestational diabetes

50g glucose challenge test at 24-28 weeks gestation (earlier if high risk)

what are risk factors for type 2 diabetes 

age ≥ 40 years 

first-degree relative with type 2 diabetes 

member of high-risk population - African, Arab, Asian, Hispanic, Indigenous, South Asian, low socioeconomic status 

history of prediabetes (IFG, IGT, A1c 6.0-6.4%)

history of gestational diabetes or delivery of a macrosomic infant (large for gestational age)

presence of end organ damage associated with diabetes 

• macrovascular: CV disease, cerebrovascular disease (stroke), peripheral vascular disease (neuropathy)

• microvascular: nephropathy, neuropathy, retinopathy

presence of vascular risk factors (obesity, HTN, hyperlipidemia)

presence of associated diseases (pancreatitis, PCOS, psychiatric disorders)

use of drugs associated with diabetes

what does a hemoglobin A1c mean

glycated hemoglobin → glycation of a protein is permanent

the lifespan of a RBC is 120 days

average blood glucose level over the 3 months

• greater weight to past 30 days

what are the units for hemoglobin A1c

percentage in canda

(ratio for international federation of clinical chemistry)

when is A1c not accurate 

recent blood loss or transfusion, sickle cell disease, thalassemia, hemodialysis, or use of erythropoietin 

what factors contribute to an A1c

fasting blood glucose

post prandial blood glucose

when does post prandial blood glucose contribute more to an A1c

A1c < 7.3

when does fasting blood glucose contribute more to an A1c

A1c > 10.2

what factors should be considered when deciding on an A1c target

age

duration of diabetes

presence of complications

• microvascular (retinopathy, nephropathy)

• macrovascular (coronary, cerebrovascular, peripheral)

• neuropathy

risk of hypoglycemia

what is a target A1c for selected adults with type 2 diabetes with potential for normoglycemia

< 6.0%

what is a target A1c for adults with type 2 diabetes to reduce the risk of CKD and retinopathy if at low risk for hypoglycemia

≤ 6.6%

what is a target A1c for most adults with type 1 or type 2 diabetes

≤ 7.0%

what is a target A1c for a patient who is functionally dependent

7.1 - 8.0%

what is an A1c target for patients with recurrent severe hypoglycemia and/or hypoglycemia unawareness, frail individuals, people with cognitive impairment, limited life expectancy

7.1 - 8.5%

how is an A1c of ≤ 7% achieved

fasting blood glucose or pre-prandial glucose 4.0-7.0 mmol/L

2-hour post prandial blood glucose 5.0-10.0 mmol/L