Sleep apnea can have various causes, depending on the type of sleep apnea:

1. **Obstructive Sleep Apnea (OSA)**:

   - **Anatomical Factors**: Such as a narrow airway, enlarged tonsils or adenoids, or a large tongue.

   - **Excess Weight**: Obesity is a significant risk factor as it can lead to fat deposits around the upper airway, obstructing breathing.

   - **Age**: Older adults may have reduced muscle tone in the throat.

   - **Gender**: Men are more likely to develop OSA than women, though the risk for women increases after menopause.

   - **Family History**: There may be a genetic predisposition to having a smaller airway or other anatomical features that contribute to OSA.

2. **Central Sleep Apnea (CSA)**:

   - **Medical Conditions**: Such as heart disorders (like congestive heart failure), stroke, brain tumor, or neurological diseases that affect the brainstem's control of breathing.

   - **Medications**: Opioid medications, especially when taken in high doses, can suppress breathing and lead to CSA.

   - **High Altitude**: Some individuals may develop CSA at high altitudes due to the effects of reduced oxygen levels.

3. **Complex Sleep Apnea Syndrome**:

   - This condition typically develops in individuals with OSA who use continuous positive airway pressure (CPAP) therapy. It involves a combination of obstructive and central sleep apnea.

Other factors that can contribute to or exacerbate sleep apnea include:

- **Alcohol and Sedatives**: These substances can relax the muscles in the throat, making it more likely for the airway to collapse.

- **Smoking**: Smoking can increase inflammation and fluid retention in the upper airway.

- **Nasal Congestion**: Conditions that cause nasal congestion or obstruction, such as allergies or deviated septum, can contribute to sleep apnea.

- **Neck Circumference**: Individuals with a thicker neck circumference may have narrower airways.

- **Sleep Position**: Sleeping on your back can worsen OSA because gravity can cause the tongue and soft tissues to collapse into the airway.