The risk factors for developing sepsis span a wide range, from age and chronic illness to hospital procedures and lifestyle. Sepsis occurs when the body’s response to an infection spirals out of control and begins damaging its own organs. Understanding what puts someone at higher risk can help you recognize vulnerability in yourself or someone you care for.
Age: The Strongest Demographic Factor
Age sits at the top of nearly every sepsis risk list. More than half of all sepsis cases are diagnosed in people aged 65 or older, and roughly 60% of severe sepsis cases in the United States occur in that age group. The rate of sepsis in older adults has been rising about 20% faster than in younger adults, partly because aging weakens immune defenses and partly because older people tend to carry more chronic health conditions.
Infants under one year old are also at elevated risk. Their immune systems are still developing, which makes it harder for their bodies to contain infections before they spread.
Chronic Health Conditions
Several long-term illnesses make infections more likely to progress to sepsis. Diabetes is one of the most significant. People with diabetes tend to have impaired immune function, slower wound healing, and higher rates of infection overall, especially when blood sugar is poorly controlled. Diabetes during pregnancy carries particular risk: one study found it increased the odds of postpartum sepsis more than sixfold.
Chronic kidney disease, chronic lung disease, coronary artery disease, and hypertension all appear as independent risk factors in large population studies. These conditions don’t just make you more susceptible to infection. They also reduce your body’s ability to tolerate the stress of fighting one, which is the mechanism that tips infection into organ failure.
Weakened Immune Systems
Anything that suppresses your immune system raises your sepsis risk substantially. Cancer patients face a compounded threat: the cancer itself can impair immune function, and treatments like chemotherapy damage rapidly dividing cells throughout the body, including the bone marrow cells that produce infection-fighting white blood cells and the mucous membranes that act as physical barriers to bacteria. When those barriers break down, bacteria that normally live harmlessly in the gut can enter the bloodstream.
Organ transplant recipients take medications that deliberately dampen the immune response to prevent rejection, which simultaneously opens the door to infections. Long-term use of corticosteroids (commonly prescribed for autoimmune conditions, asthma, and inflammatory diseases) reduces the body’s ability to kill bacterial and fungal pathogens. These effects are dose-dependent and worsen when multiple immune-suppressing drugs are combined.
HIV/AIDS, autoimmune disorders, and conditions requiring biologic therapies all fall into this category. The specific type of immune defect matters: some increase vulnerability to common bacteria, while others raise the risk of unusual opportunistic infections that healthy immune systems would easily handle.
The Infections Most Likely to Cause Sepsis
Not all infections carry equal sepsis risk. CDC data from a review of adult sepsis cases found that pneumonia was the leading trigger, responsible for about 35% of cases. Urinary tract infections accounted for 25%, gastrointestinal and abdominal infections for 11%, and skin or soft tissue infections for another 11%. Knowing which infections most commonly progress to sepsis matters because early, aggressive treatment of these conditions is the most effective way to prevent it.
Hospital Stays and Invasive Devices
Being in a hospital, particularly an intensive care unit, is itself a major risk factor. Invasive medical devices create direct pathways for bacteria to enter the body, bypassing its natural defenses. Breathing tubes carry the highest risk, increasing the daily chance of developing a healthcare-associated infection more than fourfold and raising the daily risk of sepsis specifically by about 2.3 times. Central venous catheters (IV lines placed in large veins) tripled the daily risk of infection. Urinary catheters increased the daily infection risk more than eightfold, though their direct link to sepsis was somewhat lower.
Ventilator-associated infections occurred at a rate of 42 per 1,000 patient days, dramatically higher than the 6 per 1,000 days for central line infections or 8 per 1,000 days for catheter-associated urinary infections. Having multiple devices simultaneously compounds the risk further.
Surgery and Trauma
Surgical patients face sepsis risk through several pathways. Emergency surgeries carry higher risk than planned procedures because there’s less time to optimize the patient’s condition beforehand and the surgical field is more likely to be contaminated. Operations involving internal organs, where the surgical wound contacts body fluids or intestinal contents, are riskier than clean procedures on the skin surface.
Surgical site infections can develop within 30 days of an operation, or within a year if an implant was placed. Surgeries lasting more than three hours and those delayed more than 72 hours after an injury both carry elevated risk. Trauma patients, especially those with open fractures, face infection rates that can reach as high as 53% in the most severe wound classifications.
Antibiotic-Resistant Infections
When an infection involves bacteria that don’t respond to standard antibiotics, the risk of progressing to sepsis and septic shock rises sharply. Multidrug-resistant organisms like MRSA and carbapenem-resistant bacteria limit treatment options, meaning infections persist longer and have more time to trigger the cascading organ damage that defines sepsis. One study tracking bloodstream infections found mortality climbed from 3.5% in sepsis to 9.9% in severe sepsis to 28.6% in septic shock, and resistant organisms make that progression more likely.
Factors that increase the chance of encountering resistant bacteria include recent hospital stays (within the past 90 days), prior antibiotic use, and older age. Overuse and misuse of antibiotics remain the primary drivers of resistance at the population level.
Obesity and Lifestyle Factors
Morbid obesity, defined as a BMI of 40 or higher, independently increases sepsis risk by about 57% compared to people at a normal weight. Interestingly, being moderately overweight or even moderately obese did not show a statistically significant increase after researchers accounted for other health conditions. The effect appears concentrated at the extreme end of the weight spectrum.
Smoking and heavy alcohol use are typically included as covariates in sepsis research because they impair immune function and increase vulnerability to infections, particularly pneumonia and liver-related infections. While their independent contribution to sepsis risk is harder to isolate from the chronic diseases they cause, they consistently appear in risk models.
Pregnancy and Postpartum Risk
Pregnancy creates a unique set of sepsis risk factors. Women who received no prenatal care were significantly more likely to develop postpartum sepsis. Home delivery increased the odds roughly ninefold compared to facility-based births in one large study, likely reflecting differences in sterile technique and access to emergency care. Having more than three vaginal examinations during labor doubled the risk, and preterm delivery tripled it.
Puerperal sepsis remains one of the top three causes of maternal death in low- and middle-income countries, contributing to an estimated 14% of maternal deaths in some regions. Signs like vaginal discharge and lower abdominal pain after delivery were both strongly associated with sepsis onset.