Growing older is unquestionably the greatest risk factor for insulin resistance, prediabetes, and diabetes.1 However, does aging cause changes in blood glucose levels and, ultimately, type 2 diabetes? This is still being debated.2
While a small percentage of people are at a higher risk of having problems with glucose metabolism, the vast majority of people can avoid or at least delay the onset of type 2 diabetes.3 This is important because having diabetes speeds up the aging process. The relationship between aging, insulin sensitivity, and type 2 diabetes is complex, involving a number of factors such as body composition, family history, and comorbid diseases.1
How Is Diabetes Diagnosed?
According to the Centers for Disease Control and Prevention, diabetes affects 27.3 million Americans. This represents approximately 11.3% of the population. One in every five people with diabetes is unaware that they have the disease. An additional 96 million U.S. adults have prediabetes.4
Adult blood glucose targets are standardized and do not change with age. However, because age is a significant risk factor for diabetes, knowing your blood glucose is critical to understanding your risk for type 2 diabetes.
According to the American Diabetes Association and the World Health Organization, diabetes is diagnosed when you meet one of the following criteria:1
- Random plasma glucose ≥200 mg/dL (11.1 mmol/L)
- Fasting plasma glucose ≥126 mg/dL (7 mmol/L)
- 2-hour plasma glucose post-75 gram oral glucose tolerance test (OGTT) ≥200 mg/dL (11.1 mmol/L)
- Hemoglobin A1C ≥6.5%.
Prediabetes is diagnosed when your blood glucose is higher than it should be but does not meet the criteria for diabetes. It is an intermediate stage between having normal glucose tolerance and full-blown type 2 diabetes. Identifying prediabetes and making changes if you have any modifiable risk factors can prevent or at least delay the progression to type 2 diabetes.
The criteria for prediabetes include:5
- Fasting blood glucose between 100 mg/dL and 125 mg/dL
- 2-hour plasma glucose post-75 gram OGTT between 140 mg/dL and 199 mg/dL
- Hemoglobin A1C between 5.7% and 6.4%
The Centers for Disease Control and Prevention also offer a Prediabetes Risk Test you can take to get a better understanding of your risk factors.6
An isolated fasting blood glucose misses many older adults with type 2 diabetes. When 1,152 adults were tested using a hemoglobin A1C, fasting plasma glucose, and a 2-hour OGTT, 131 were diagnosed with type 2 diabetes:
- A fasting plasma glucose test only identified 40 (31%)
- A 2-hour OGTT identified 89 (68%)
- A hemoglobin A1C identified 66 (50%)
Each of these tests identifies a subset of the population, but no single test can identify everyone with type 2 diabetes.1 Knowing your level of risk for insulin resistance and type 2 diabetes can help you determine how often you should check your blood glucose.
Another study found that hemoglobin A1C levels rise with age, regardless of age-related increases in insulin resistance, diabetes and prediabetes prevalence, or glucose levels. The cause of the increase in hemoglobin A1C is unknown, but it could be related to glycation or red blood cell lifespan. This means that using age-independent reference values for hemoglobin A1C in older adults may significantly overdiagnose prediabetes and diabetes. Researchers emphasize the importance of monitoring glucose levels in addition to hemoglobin A1C. 7
Normal Blood Sugar Levels for Adults with and Without Diabetes
Normal blood sugar levels for people without diabetes differ slightly from those with diabetes. Older adults with diabetes are at an increased risk of hypoglycemia (low blood sugar).
Low blood sugar can increase the risk of:8
- Cardiovascular events such as heart attacks and chest pain
- Cognitive function declines
For this reason, older adults, especially people with medical problems, have slightly wider target ranges for blood glucose to reduce the risk of hypoglycemia.
Target Blood Sugar Ranges for Adults8,9
Adults without diabetes
- Fasting blood sugar: 70—99 mg/dL
- Before eating: 80—130 mg/dL
- 1-2 hours after eating: 80—140 mg/dL
- Bedtime target: 100—140 mg/dL
- Target hgA1C: Below 5.7%
Healthy adults with diabetes
- Fasting blood sugar: Less than 100 mg/dL
- Before eating: 80—130 mg/dL
- 1-2 hours after eating: 80—180 mg/dL
- Bedtime target: 100—140 mg/dL
- Target hgA1C: 7% or less
Older, healthy adults with diabetes
- Fasting blood sugar: 90—130 mg/dL
- Bedtime target: 90—150 mg/dL
- Target hgA1C: 7.5% or less
Adults with complex health problems
- Fasting blood sugar: 90—150 mg/dL
- Bedtime target: 100-180 mg/dL
- Target hgA1C: 7.5% or less
Adults with very poor health and complex medical problems
- Fasting blood sugar: 100—180 mg/dL
- Bedtime target: 110—200 mg/dL
- Target hgA1C: 8.5% or less
<p class="pro-tip">Read more about average blood sugar levels for people without diabetes.</p>
How Aging Affects Blood Sugar Levels
Insulin and glucagon are pancreatic hormones that regulate blood glucose levels.
Carbohydrates and other nutrients are broken down and absorbed into the bloodstream after eating. When blood glucose rises, a healthy pancreas produces more insulin.
Insulin activates transporters in the cell membrane, allowing glucose to enter our cells and be used for energy. Excess glucose is stored as glycogen in the muscle and liver. Insulin helps your body's cells use glucose effectively and regulates fatty acid release from adipose (fat) cells. This process becomes less efficient with age.
How Age-Related Muscle Changes Lead to Insulin Resistance
Skeletal muscle can absorb up to 85% of circulating blood glucose in a healthy person. But, muscle mass decreases with age, and this process also becomes less efficient. The result: glucose stays in the bloodstream for longer periods.1
A decrease in muscle mass is a major factor that contributes to insulin resistance with aging.
However, there are other age-related changes in muscles that also contribute to insulin resistance, including:
- An increase in mitochondrial dysfunction—makes it more difficult to convert macronutrients to energy.
- A decrease in mitochondrial number—there is a positive correlation between the number of skeletal muscle mitochondria and insulin sensitivity.
- Increased inflammation—increases insulin resistance.
- An increase in fat deposits—As lipids (fats) increase in muscle cells, they affect enzymes involved in the insulin signaling pathway and increase inflammation.
- Exposure to more oxidative stress—makes metabolism less efficient and increases insulin resistance.
- Decreased ability to get rid of nonfunctional or poorly functioning muscle cells.
- An overactive renin-angiotensin system—increases inflammation and oxidative stress.
These changes reduce skeletal muscle insulin sensitivity and increase the risk of type 2 diabetes.
Exercise can improve or at least reduce the impact of many of these changes in skeletal muscle associated with aging.
About 50% of insulin is secreted continuously at a baseline level in small pulses. The other 50% is released in larger spikes in response to stimulation stimulated. A pulsatile secretion, instead of continuous, is important to regulate glucose release from the liver and to keep muscle cells in a state of metabolic readiness to absorb excess glucose from the blood. If insulin secretion was continuous, feedback loops would not work effectively, and your body cells would adapt to increased insulin secretion.3
Fasting older adults without diabetes have disorderly insulin pulses with reduced amplitude and frequency. People with type 2 diabetes also have disorganized pulsatile insulin release.3
Rising blood glucose stimulates insulin release from the pancreas, but insulin does not act alone. Incretins released from the gut in response to a meal account for roughly half of the stimulation to release insulin. Incretins include gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Incretin levels do not appear to decrease with age. In fact, they may increase. GIP sensitivity declines with age and is completely lost in type 2 diabetes. GLP-1 sensitivity does not decline with age or in type 2 diabetes. This is why GLP-1 agonists are used to treat type 2 diabetes.3
Why Do Blood Sugar Levels Increase With Age?
Some people lose the ability to regulate their blood glucose as well as they did when they were younger. Increased body fat and decreased physical fitness are major contributors to a decline in glucose tolerance between young adulthood and middle age. 1
Even after accounting for changes in body composition and physical activity, researchers found that changes in glucose tolerance between the ages of 60 and 92 remain significant. In one study, researchers discovered that hemoglobin A1C increased by about 0.03 points per year in people who did not have diabetes. They also noticed a slight increase in fasting blood glucose levels and a larger increase in 2-hour OGTT results.10
Participants in the NHANES II study, a large clinical trial, had a 0.4 mm/decade increase in mean fasting blood glucose. 11 It is unclear whether increasing A1C and 2-hour OGTT results reflect an increase in insulin resistance or another process.
Insulin resistance occurs when your pancreas needs to produce more insulin to regulate your blood sugar because your body cells have become resistant to its effects. The insulin-producing beta cells in your pancreas will produce as much insulin as possible for as long as possible until they burn out. Among the possible causes of insulin insensitivity with aging are:2
- Increased belly fat: Abdominal fat is metabolically active.12 It accounts for 25% to 35% of the variability in insulin activity13 and 60% to 85% of insulin resistance overall.14 An increase in abdominal fat is associated with high blood pressure and a decrease in insulin sensitivity.15 Increased abdominal fat wedged between organs has decreased blood supply and, as a result, becomes inflamed. Fat cells secrete chemicals that increase insulin resistance, and insulin resistance increases fat deposition, setting up a vicious cycle.14
- Decreased muscle mass: A decline in physical activity, inadequate protein intake, changes in nervous system function, and declines in anabolic hormones such as testosterone result in a decrease in muscle mass. Muscle is essential in moderating blood sugar by absorbing excess glucose from the bloodstream.16 Reduced muscle mass can mean glucose stays in the bloodstream longer.
- Changes in mitochondrial efficiency: Mitochondria are organelles inside every cell that convert the energy stored in chemical bonds in food into adenosine triphosphate (ATP), which is the energy currency each cell in your body uses to power growth, repair, and movement. When comparing older to younger adults, researchers discovered that mitochondrial efficiency decreased by 40%. This can lead to increased muscle fatigue and increased fat deposits in muscle. Changes in mitochondrial function in the pancreas may also affect insulin release.17
- Hormonal changes: Decreases in anabolic hormones such as IGF-1, testosterone, and dehydroepiandrosterone (DHEA) that are important for building muscle and maintaining bone density result in increased body fat and decreased physical fitness.18
- Increased oxidative stress: Metabolizing food into energy results in unpaired electrons. These unpaired electrons bind to DNA and other cellular structures, causing damage and changes in cell structure. Oxidative stress is thought to contribute to the aging process.
- Inflammation: Muscle cells can become inflamed due to excess fatty acids. Inflamed muscle becomes resistant to insulin, and excess glucose is used to make fat. As a result, fat is deposited in the liver, muscle, and adipose tissue. Read more about how to reduce inflammation.
- Obesity: Obesity, particularly abdominal obesity, is the most important contributor to the aging process, frailty, and insulin resistance. According to one study, there is a link between decreased quadriceps muscle strength per kilogram of muscle mass and insulin resistance. Insulin stimulates the production of muscle proteins. These findings are consistent with those of the Diabetes Prevention Program. Adults who exercise are the least likely to develop type 2 diabetes from insulin resistance. 19
Why It Matters: The Importance of Blood Glucose Awareness and Control
With age, prediabetes and diabetes are more prevalent, and older adults are at increased risk for complications from diabetes.8
However, researchers at the Johns Hopkins Bloomberg School of Public Health found that older adults (over age 70) with prediabetes don’t usually develop type 2 diabetes. In their study, 12% of older adults with elevated blood glucose progressed to diabetes, but a higher percentage regressed to normal blood glucose. Prediabetes is still considered a predictor of type 2 diabetes for young and middle-aged adults.20
Nearly 38% of the U.S. adult population has prediabetes.4 While prediabetes is a common condition, that does not mean it should not be taken seriously. Prediabetes is associated with an increased risk of:21
- Cardiovascular disease
- Coronary heart disease
- All-cause mortality
Type 2 diabetes also increases the risk of:
- Chronic kidney disease
- Small vessel disease
- Immune dysfunction
Increased blood glucose damages the inner lining of blood vessels. Your heart must pump harder to overcome the increased resistance that narrowed and scarred blood vessels impose. Increased friction along blood vessel walls can also increase the risk of blood clots. Blood vessel damage secondary to high blood glucose levels affects people of all ages, but the risk of cardiovascular disease from high blood glucose is much higher in older adults.3
As insulin resistance progresses, it can lead to metabolic syndrome, nonalcoholic fatty liver disease, high blood pressure, abnormal blood lipids, and type 2 diabetes mellitus.22 Of these, the most common consequence of uncontrolled blood sugar and insulin resistance is type 2 diabetes. Insulin resistance is thought to precede type 2 diabetes by about 10 to 15 years.23 This lead time is the ideal opportunity to identify whether you are at increased risk for type 2 diabetes and make any lifestyle changes you can to decrease that risk. Read more about the many benefits of having stable blood sugar.
Does Gender Make a Difference?
In a study that enrolled 12.8 million participants, researchers found that:24
- Men had a 3.0mg/dL higher fasting glucose than women had until age 73 years
- After age 73, women had higher fasting glucose levels than men
- Fasting glucose increased with age until age 62 to 63 years
- Women had an increase in fasting glucose starting at age 28 and continuing to 86 to 99 years
- The peak difference between the sexes was at 48-51 years, where men had a 6.1 mg/dL higher fasting glucose level than women
- Fasting glucose levels between 80 and 94 mg/dL were associated with the lowest mortality, regardless of age and sex
<p class="pro-tip"><strong>Learn about </strong> <a href="/blog/what-factors-affect-blood-sugar">more factors that can affect your blood sugar</a>.</p>
Things You Can Do to Manage/Reduce Blood Glucose Levels as You Get Older
There are many steps you can take to manage your blood glucose and improve your overall health. Every lifestyle change you make to reduce your risk of type 2 diabetes also reduces your risk of cardiovascular disease, cancer, kidney disease, obesity, and the many other diseases associated with uncontrolled blood glucose.
Manage Your Weight
Many factors contribute to increased weight gain with aging, including a gradual loss of muscle mass, decreased physical activity, declines in estrogen and testosterone, and a decrease in fat-burning response to catecholamines.1 Losing even 5% to 10% of excess weight can greatly affect your overall health.
Any type of physical activity can help improve your glucose sensitivity and help with weight management. The Centers for Disease Control and Prevention and the American Heart Association recommend adults engage in 150 minutes per week of moderate aerobic exercise, 75 minutes of vigorous exercise, or a combination of both, and resistance exercise to strengthen all major muscle groups two days per week.25
Exercise increases glucose uptake into skeletal muscle by 50-fold.26 In one study, exercise was more effective than metformin (a diabetes drug) in controlling blood sugar and reducing the risk of cardiovascular disease in adults with type 2 diabetes.27
Monitor Your Sugar Intake
Minimize consumption of simple and processed sugars. According to a U.S. Department of Agriculture report, the average American consumes 156 pounds of sugar yearly. Reduce sugar consumption by choosing whole foods whenever possible and watching for added sugar in processed foods.
Get Adequate Vitamin D
Vitamin D helps regulate insulin secretion, increase insulin sensitivity, and reduce inflammation.28 Just 20 minutes in the sunshine twice weekly can provide enough exposure to ultraviolet B radiation to meet your vitamin D requirements.
Consider supplements or choose foods enriched in vitamin D to meet the 600 IU of vitamin D recommended by the Institute of Medicine for adults 19 to 70 or the 800 IU recommended for adults over age 70, with an upper limit of 4,000 IU.29 The Endocrine Society recommends slightly higher doses: 1,500 to 2,000 IU for adults 19 and older.30
Get Plenty of Restful Sleep
Disrupted or inadequate sleep can increase your risk of metabolic syndrome, high blood pressure, abnormal blood lipids, type 2 diabetes, cardiovascular disease, and insulin resistance.31 Try to prioritize a bedtime routine and aim for 7 to 8 hours of restful, uninterrupted sleep each night. For more tips, read Improving Sleep Quality: How to Not Wake Up Tired.
Choose a Healthy Diet
High fiber, high protein, and foods that are healthy sources of fats are everyday foods that stabilize blood sugar levels. For more ideas on building a healthy diet full of nutritious foods that can stabilize your blood sugar, read the ultimate list of high-fiber, low-carb foods.
How a Continuous Glucose Monitor (CGM) and the Signos App Can Help
Metabolic changes typically begin 10 to 13 years before type 2 diabetes is diagnosed. Early detection of changes in glucose sensitivity provides more opportunities to make lifestyle changes that may delay or even prevent type 2 diabetes. Studies have shown that a single fasting blood glucose, hemoglobin A1C or 2-hr OGTT may miss many people later diagnosed with type 2 diabetes.1
Using a CGM and the Signos app, you can track your blood sugar and identify trends. Knowing which lifestyle factors influence your blood glucose levels, as well as how much, and how to mitigate your glucose spikes, can help you reduce your risk of type 2 diabetes and its associated diseases.
A CGM and the Signos app provide you with real-time data on how your body reacts to the foods you eat, as well as recommendations on how to make small tweaks to your diet that can have a big impact over time.
Optimizing your metabolic health is a lifelong endeavor that should be prioritized by anyone who wants to maximize their number of disease-free years.
Get more information about weight loss, glucose monitors, and living a healthier life
Topics discussed in this article:
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