Researchers studied over 250,000 adults to understand if low vitamin D levels make sleep apnea more likely. Sleep apnea is a condition where breathing stops and starts during sleep. The study found that people with low vitamin D were about 26% more likely to develop sleep apnea compared to those with healthy vitamin D levels. The connection was strongest in women, younger adults, and people who were overweight. This suggests that maintaining good vitamin D levels might help prevent sleep apnea, though more research is needed to confirm this relationship.

The Quick Take

  • What they studied: Whether people with low vitamin D levels are more likely to develop obstructive sleep apnea (a condition where breathing repeatedly stops during sleep) compared to people with normal vitamin D levels.
  • Who participated: Over 253,000 adults aged 18 and older from multiple hospitals and health systems across the United States between 2010 and 2023. Researchers matched people with low vitamin D to similar people with normal vitamin D to make fair comparisons.
  • Key finding: Adults with low vitamin D had a 26% higher risk of developing sleep apnea over five years (5.7% developed it versus 4.4% in the normal vitamin D group). This difference was statistically significant, meaning it’s unlikely to be due to chance.
  • What it means for you: If you have low vitamin D, getting your levels checked and corrected might help reduce your risk of developing sleep apnea. This is especially important if you’re a woman, under 65, or overweight. However, this study shows an association, not definite proof that low vitamin D causes sleep apnea, so talk to your doctor about your individual risk.

The Research Details

This was a retrospective cohort study, which means researchers looked back at health records from 2010 to 2023 to see what happened to people over time. They used a large network of hospitals called TriNetX that combines medical records from many institutions. Researchers identified adults with low vitamin D (defined as 20 ng/mL or lower) and matched them one-to-one with similar adults who had normal vitamin D levels (30 ng/mL or higher). To make sure the vitamin D levels were accurate, they required all participants to have a second vitamin D test within 3-12 months of the first one. They then followed both groups for up to 5 years to see who developed sleep apnea.

The researchers used a statistical technique called propensity score matching to make the two groups as similar as possible in terms of age, weight, and other health factors. This helps ensure that any differences in sleep apnea rates are due to vitamin D levels rather than other factors. They also waited three months after the vitamin D measurement before counting new sleep apnea cases, which helps reduce the chance that sleep apnea symptoms caused the low vitamin D rather than the other way around.

The study examined whether the relationship between vitamin D and sleep apnea was different in various groups, such as men versus women, younger versus older adults, and people of different weights. This helps identify who might benefit most from vitamin D treatment.

This study design is stronger than previous research because it follows people forward in time rather than just looking at a single point in time. By requiring confirmatory vitamin D measurements and waiting three months before counting new sleep apnea cases, the researchers reduced the chance of errors and made it more likely they were seeing a real cause-and-effect relationship rather than just a coincidence.

Strengths of this study include its large sample size (over 250,000 matched pairs), use of real medical records from multiple hospitals, careful matching of comparison groups, and follow-up over several years. The study also looked at different groups separately to see if vitamin D’s effect varied. Limitations include that it’s observational (not a controlled experiment), so we can’t be completely certain vitamin D deficiency causes sleep apnea. The study also relied on medical records, so some cases of sleep apnea might have been missed if people didn’t get tested. Additionally, the study didn’t measure other factors that might affect vitamin D or sleep apnea, such as sun exposure, diet, or exercise habits.

What the Results Show

Among the 253,126 matched pairs studied, 5.7% of people with low vitamin D developed sleep apnea during the follow-up period, compared to 4.4% of people with normal vitamin D levels. This means people with low vitamin D had a 26% higher risk (expressed as a hazard ratio of 1.26). The researchers were very confident in this finding because the statistical analysis showed it was extremely unlikely to occur by chance (p < 0.001, meaning less than 1 in 1,000 probability of being wrong).

The relationship between vitamin D and sleep apnea was not the same for everyone. Women showed a stronger connection than men, with women having a 32% higher risk compared to men’s 19% higher risk. Younger adults (under 65) showed a much stronger connection than older adults, with younger people having a 45% higher risk compared to older people’s 15% higher risk. People who were overweight or obese showed a 27% higher risk, while people at normal weight showed almost no increased risk (only 2% higher).

The study found evidence of a dose-response relationship, meaning that the lower someone’s vitamin D level, the higher their sleep apnea risk tended to be. This pattern supports the idea that vitamin D deficiency might actually cause sleep apnea rather than just being associated with it by chance.

The subgroup analyses revealed important patterns about who is most affected by low vitamin D. The interaction between vitamin D and sleep apnea risk was significantly different across sex, age, and weight categories. Women, younger adults, and overweight or obese individuals showed much stronger associations between low vitamin D and sleep apnea risk. These findings suggest that vitamin D supplementation or correction might be particularly beneficial for these high-risk groups.

Previous research has mostly looked at vitamin D and sleep apnea at a single point in time, making it hard to know which came first. This study is stronger because it follows people forward in time and requires confirmation of vitamin D levels. The findings align with smaller studies suggesting a connection between vitamin D and sleep apnea, but this is the largest study to date examining this relationship in a way that better supports cause-and-effect conclusions.

This study has several important limitations. First, it’s observational, meaning researchers watched what happened naturally rather than randomly assigning some people to take vitamin D and others not to. This makes it harder to prove that low vitamin D actually causes sleep apnea. Second, the study relied on medical records, so some people with sleep apnea might not have been diagnosed or recorded. Third, the researchers didn’t have information about other important factors like how much sun exposure people got, their diet, exercise habits, or other health conditions that might affect both vitamin D and sleep apnea. Fourth, the study population came from hospital networks, so results might not apply to all populations. Finally, while the study waited three months after vitamin D measurement to count new sleep apnea cases, there’s still a possibility that undiagnosed sleep apnea affected vitamin D levels rather than the other way around.

The Bottom Line

Based on this research, maintaining adequate vitamin D levels (above 30 ng/mL) appears to be associated with lower sleep apnea risk. If you have low vitamin D, talk to your doctor about testing and possible supplementation. This recommendation is particularly important if you’re a woman, under 65 years old, or overweight. However, this study shows an association, not definite proof, so vitamin D supplementation should be part of a broader approach to sleep apnea prevention that includes maintaining a healthy weight and good sleep habits. Confidence level: Moderate—this is strong evidence of an association, but more research is needed to prove vitamin D supplementation directly prevents sleep apnea.

This research is most relevant for women, younger adults (under 65), and people who are overweight or obese, as these groups showed the strongest associations. Anyone with symptoms of sleep apnea (loud snoring, gasping for breath at night, daytime sleepiness) should see a doctor regardless of vitamin D status. People with known vitamin D deficiency should discuss testing and treatment with their healthcare provider. This research is less directly applicable to older adults and people at normal weight, though maintaining adequate vitamin D is still important for overall health.

If you start correcting low vitamin D levels, it may take several months to a year to see the full effects on sleep apnea risk. Vitamin D levels typically improve within weeks of supplementation, but the protective effect against sleep apnea development would likely take longer to become apparent. Don’t expect immediate changes in sleep quality, but consistent vitamin D maintenance over months may help reduce your long-term risk.

Want to Apply This Research?

  • Track your vitamin D supplementation daily and log your vitamin D blood test results when available. Set a reminder to check vitamin D levels every 6-12 months. Also track sleep quality metrics like snoring frequency, daytime sleepiness (on a scale of 1-10), and number of times you wake up gasping at night.
  • If your vitamin D is low, commit to daily supplementation as recommended by your doctor (typically 1,000-4,000 IU daily, but follow your doctor’s specific recommendation). Pair this with other sleep apnea prevention strategies: maintain a healthy weight, sleep on your side instead of your back, and avoid alcohol before bed. Log these behaviors in the app to track consistency.
  • Set up monthly check-ins to review your vitamin D supplementation adherence. Every 6 months, review your sleep quality metrics to see if they’re improving. Schedule annual vitamin D blood tests and log the results. If you’re in a high-risk group (woman, under 65, overweight), prioritize this tracking. Share your vitamin D levels and sleep metrics with your doctor at annual checkups to adjust your supplementation if needed.

This research shows an association between low vitamin D and increased sleep apnea risk, but does not prove that vitamin D deficiency causes sleep apnea. This information is for educational purposes only and should not replace professional medical advice. If you suspect you have sleep apnea (symptoms include loud snoring, pauses in breathing during sleep, or excessive daytime sleepiness), consult a healthcare provider for proper diagnosis and treatment. Before starting any vitamin D supplementation, especially at high doses, discuss with your doctor, as excessive vitamin D can be harmful. Individual vitamin D needs vary based on age, health status, and other factors—your doctor can determine the right level for you. This study was observational and cannot prove cause-and-effect; more research is needed to confirm whether vitamin D supplementation prevents sleep apnea.