Night sweats with a sour or vinegary odor can be concerning, but it’s not necessarily related to aging or something like "old people smell." Instead, it could point to a number of potential causes, which are worth investigating. Since you’ve never experienced this before, it’s good to take it seriously. Here are some things to consider:

1. Hormonal Changes:
At 41, you may be starting to experience hormonal changes leading up to perimenopause (the phase before menopause). Hormonal fluctuations, particularly changes in estrogen levels, can lead to night sweats. These sweats can sometimes have a distinct odor, as the body works harder to regulate temperature.
2. Diet and Dehydration:
Certain foods (like spicy foods, alcohol, or high-fat meals) or dehydration can sometimes cause body odor, particularly at night. This might be amplified if you sweat during sleep, and sweat can mix with bacteria on your skin, producing a sour smell.
3. Infections or Medical Conditions:
Fungal infections (such as yeast infections) or bacterial infections can cause a sour smell. These might be more noticeable when you're sweating.
Liver or kidney problems can sometimes manifest through changes in body odor, but these conditions typically come with other symptoms like fatigue, swelling, or changes in urine output.
Thyroid issues (such as hyperthyroidism) can cause sweating and changes in body odor, but this would typically be accompanied by other symptoms like weight changes, heart palpitations, or fatigue.
4. Stress and Anxiety:
Anxiety or stress can trigger night sweats, and the resulting odor could be influenced by sweat reacting with your skin’s natural bacteria.
5. Medications:
If you’ve started any new medications recently, some drugs can cause sweating and changes in body odor.
What You Can Do:
Track your symptoms: Keep a log of when the night sweats happen, how often, and whether there’s any correlation with diet, stress, or medications.
Personal hygiene: Make sure you're keeping your skin clean and dry at night. Consider using breathable, moisture-wicking fabrics for sleepwear and bedding.
Consult a doctor: If the symptoms persist or if you notice other signs like fatigue, changes in weight, or swelling, it’s a good idea to see a healthcare provider. They can run tests to check for hormonal changes, thyroid issues, or other underlying conditions.
In summary, while it’s unlikely to be related to aging specifically, it’s worth looking into these factors further with the help of a medical professional.