Hi,
I'm not a doctor, so my advice would be to do whatever you pulmonologist recommends.
If you have COPD/emphysema,, OSA can worsen lung function and increase risks like heart strain or low oxygen levels (hypoxemia).
I found a 2021 study in Sleep Medicine Reviews that said untreated mild OSA is associated with a modest increase in cardiovascular risk (e.g., hypertension, heart disease) over time, but immediate CPAP may not be necessary unless symptoms or comorbidities are significant. However, a 2018 study in Thorax found that CPAP in overlap syndrome patients with mild OSA (AHI 5–15) improved lung function and reduced hospitalizations compared to no treatment, but benefits were less pronounced than in moderate/severe cases. But, the exact opposite was found in A 2017 study in European Respiratory Journal that found untreated overlap syndrome leads to faster lung function decline and higher exacerbation rates. So the studies are conflicting, and we're all different, that's why its best speaking with your pulmonologist.
Alternative Therapies may be worth considering. For mild OSA, a mandibular advancement device (MAD) fitted by a dentist can keep airways open, though less effective than CPAP.
FDA-approved devices like NightShift prevent back sleeping, suitable for positional OSA.
Good luck with it.