Co-morbidities are underlying medical or health conditions that may slow wound healing. This article will take a closer look at typical comorbidities in patients, e.g., diabetes, immune system deficiency, peripheral vascular disease, wound infection, peripheral neuropathy, aging, stress, and malnutrition. 

Diabetes

Diabetes is one of the most frequent causes of chronic foot ulcers, with a prevalence of 15%. According to the CDC, over 34 million Americans, or 1 in every 10 Americans, are diabetic. People living with diabetes often have low circulation to the limbs. Low circulation results from the stiffening and constriction of the artery walls (aka atherosclerosis), depriving the wound of blood and oxygen needed for cell migration and revascularization. High blood sugar (hyperglycemia) also lowers the efficiency of leukocytes that fight infection. 

Immune System Deficiency

The immune system protects the body against harmful microorganisms and is responsible for causing inflammation to facilitate wound healing. However, age, malnutrition, or chronic disease can lower immune function, resulting in slow-to-heal wounds. Immunodeficiency also compromises the body's ability to fight off infections. Infected wounds remain in the inflammatory phase for longer than necessary and show impaired cellular migration and revascularization. Immune system deficiency may be caused by genetics, chemotherapy, radiation, malnutrition, etc. 

Peripheral Vascular Disease (PVD)

Peripheral vascular disease occurs due to a constriction or malfunctioning of arteries (arterial insufficiency) or veins (venous insufficiency) supplying blood to the lower extremities. The resulting poor circulation deprives the wound of oxygen and nutrient-rich blood, causing delayed healing. Some risk factors for PVD include high blood cholesterol, diabetes, old age, and smoking. For arterial insufficiency, if left untreated, clot formation occurs, which can entirely block the peripheral arteries. 

PVD is a leading cause of lower-limb amputations annually. Some symptoms of arterial insufficiency include pain in the legs during ambulation that eases when a patient is at rest, a loss of sensation and pulses in the affected limbs, and open sores that are slow to heal. For venous insufficiency, symptoms include edema (swelling in the feet due to fluid retention in the tissues), pain in the legs during ambulation that eases when a patient is at rest, skin discoloration, erythema and scaling, and shallow, wide wounds that are slow to heal. 

Wound Infection

Wounds become infected when bacteria living on the surface of the skin gain access into the body through broken or excavated skin, proliferate and activate an immune response. Infection is a leading cause of slow-healing wounds, causing damage to tissues and inflammation. Infection may be localized (confined to the wound site) or systemic (affecting the entire body). Symptoms of infected wounds include increased pain, chills or fever, edema, erythema, and purulent exudate, commonly called "pus."

Peripheral Neuropathy

Peripheral neuropathy occurs when there is damage to the blood vessels supplying blood to the lower extremities, which results in impaired wound healing. This condition is common in people living with diabetes, and the nerve damage results in a loss of sensation in the feet. Not being able to feel developing or infected wounds on the feet can prevent patients from receiving wound care promptly. 

Aging

As we age, our skin tends to become less elastic and more fragile. Wound healing is delayed with age and seniors (aged 60 and older) tend to have more scarring as wounds heal. Collagen production is also lower in elderly patients, which may result in slower wound healing. Chronic wounds, such as venous ulcers, arterial insufficiency ulcers, and pressure ulcers tend to have a significantly higher prevalence in patients aged 65 and above due to a higher incidence of diabetes and cardiovascular disease which lowers circulation to the lower extremities. 

Stress

Another comorbidity affecting the rate of healing in wounded patients is psychological stress. According to research by Jean-Philippe Gouin et. al, psychological stress can have a direct impact on the healing process and also indirectly impacts healing by promoting health-damaging behaviors. Using the punch-biopsy model to create full-thickness dermal wounds and mucosal wounds, researchers found that it took caregivers 24% longer to heal the wounds due to heightened levels of anxiety and depression. The other factors outlined in the study include stress-induced glucocorticoid and catecholamine production, oxytocin and vasopressin levels in women and men, and diminished expression of proinflammatory cytokines at the wound site. 

Malnutrition

Due to the higher energy and nutrient demands placed on the body to support wound healing processes, adequate intake of nutrients is vital. According to research, nutritional deficiencies have been linked to lower wound tensile strength and a heightened risk of infection. Macronutrients (such as fats, proteins, and carbohydrates) and micronutrients (including amino acids and vitamins) in adequate quantities lowers the risk of wound infection and facilitates angiogenesis, fibroblast production, and collagen synthesis, all known to promote faster wound closure and repair.