A new Canadian study suggests fluoride exposure may be associated with sleeping fewer hours than recommended for optimal health.
Key findings include:
- Higher levels of fluoride in tap water were associated with a 34% increased risk of sleeping less than recommended.
- The association remained after adjusting for factors like age, BMI, income, ethnicity, and health conditions.
- No link was found between fluoride exposure and other sleep issues like insomnia or daytime sleepiness.
- The study included over 1,300 Canadians aged 16-79 years.
- Around 32% lived in areas with fluoridated tap water.
Source: Environ Health. 2021
The Impact of Insufficient Sleep
Not getting enough sleep is a common issue, affecting around 30% of adults.
Habitual short sleep duration has been tied to numerous health risks.
These include obesity, high blood pressure, heart disease, diabetes, depression, and impaired cognitive function.
Getting sufficient restorative sleep is crucial for physical health, mental health, productivity, and quality of life.
Understanding what factors contribute to insufficient sleep is important for public health efforts.
While lifestyle choices and sleep disorders play a major role, environmental exposures may also affect sleep.
The evidence linking fluoride to shorter sleep times adds a new piece to the puzzle.
Fluoride-Sleep Study in Toronto Canada
The study was led by researchers at York University in Toronto, Canada.
It used data from a national health survey conducted in 2012-2013.
The analysis included over 1,300 Canadians aged 16-79 years.
Around 32% lived in communities with fluoridated tap water.
The rest lived in areas with non-fluoridated water.
Fluoride exposure was measured in two ways:
- Tap water fluoride concentration
- Fluoride levels in urine samples
Self-reported sleep duration and sleep problems were assessed with questionnaire items.
Participants reported how many hours they sleep in a typical 24-hour period.
They also shared how often they have trouble sleeping or staying asleep, and difficulty staying awake during the daytime.
Key Findings: Fluoride and Sleep Duration
The key finding was that higher fluoride levels in tap water were associated with sleeping fewer hours per night:
- For every 0.5 mg/L increase in water fluoride, there was a 34% higher risk of sleeping less than recommended for the person’s age.
- People aged 16-17 years are advised to sleep 8-10 hours per night. Adults 18-64 years old 7-9 hours, and adults 65+ years old 7-8 hours.
- The association was significant even after adjusting for demographics, BMI, income, ethnicity, and health conditions.
- When the data was weighted to represent the Canadian population, the association grew even stronger.
- No link was found between fluoride exposure and other sleep issues like insomnia or daytime sleepiness.
The results suggest fluoride specifically affects sleep duration, not overall sleep quality. However, the underlying mechanisms are still unknown.
More research is needed to confirm the finding and better understand the impacts of fluoride on sleep.
Potential Explanations for Shorter Sleep from Fluoride
The researchers proposed several ways fluoride could potentially affect sleep duration:
Melatonin Hypothesis
Fluoride accumulates in the pineal gland, which produces the sleep-regulating hormone melatonin.
Studies in animals suggest fluoride may reduce melatonin levels.
Low melatonin could delay sleep onset, theoretically shortening the total sleep time.
However, melatonin was not measured in this study.
Oxidative Stress
Fluoride may induce oxidative stress by generating reactive oxygen species (ROS).
ROS damage cells and impair tissue function.
The antioxidant melatonin helps counter oxidative stress.
If fluoride reduces melatonin, it could allow more oxidative damage in the brain.
But more research is needed on fluoride’s role in ROS production and neural oxidative stress.
Other Mechanisms
Fluoride could potentially affect sleep via other pathways like the thyroid or cardiovascular system.
But more studies are needed to elucidate alternative mechanisms.
The cross-sectional design of this study limits the ability to determine cause-and-effect relationships.
Strengths and Limitations of this Study
The study had several notable strengths:
- Large population-based sample of Canadians from diverse areas
- Objective measures of fluoride exposure from water and urine samples
- Included adults across a wide age range
However, there were also important limitations to consider:
- Cross-sectional design, so unable to determine cause-and-effect
- Self-reported sleep duration, not objective measures
- Did not assess factors like sleep disorders, diet, exercise, medication use
- Basic single-item measures of sleep problems and daytime sleepiness
- Potential issues with high variability in spot urine samples
The simplicity of the sleep measures may explain why fluoride was only linked to sleep duration, not quality issues. The lack of data on health conditions and behaviors that affect sleep is another major limitation.
No Evidence that Fluoride Directly Impairs Sleep
This preliminary study alone does not prove fluoride directly impairs sleep.
However, if confirmed by more rigorous research, the public health implications could be significant.
Even a modest sleep-disrupting effect could have a meaningful impact on population health.
Insufficient sleep is very common, yet often overlooked relative to diet and exercise.
Getting enough high-quality sleep is crucial for physical and mental health.
Environmental exposures that may harm sleep deserve close scrutiny due to potential widespread impacts.
Around 39% of Canadians have fluoridated municipal tap water.
Rates are higher in the US, affecting over 60% of those with public water supply.
Any potential downsides of fluoride must be carefully weighed given its benefits for dental health.
But more research is warranted to elucidate and potentially mitigate any unintended consequences of water fluoridation.
Studies in children and adolescents have also reported adverse effects of fluoride on neurodevelopment, at levels considered safe for oral health.
Science must continue investigating the full spectrum of fluoride’s health effects across all age groups.
Benefit-risk assessments may need to be regularly re-evaluated as new evidence emerges.
Fluoride & Sleep: Preliminary Findings
This study provides preliminary evidence that fluoride exposure may contribute to shortened sleep duration.
However, the limitations preclude drawing firm conclusions at this time.
More rigorous research is needed to confirm and expand on the findings before implications for public health policy can be considered.
Key next steps include:
- Prospective cohort studies relating long-term fluoride exposure to objectively measured sleep over time
- Clinical trials of fluoride reduction with sleep outcomes
- Research on potential biological mechanisms like melatonin, oxidative stress pathways
- Studies in populations with wider range of fluoride exposures
- Assessing interactions of fluoride with behaviors, health conditions, medications
- Examining effects on sleep quality, daytime sleepiness, and circadian rhythms
- Research in children to understand early life exposures
Hopefully this thought-provoking study will spur additional research illuminating fluoride’s impacts on sleep and health across the lifespan.
While more evidence is still needed, people concerned about insufficient sleep may want to consider reducing fluoride exposure from water, dental products, and other sources as a precaution.
Drinking non-fluoridated water is an easy way to significantly lower exposure.
But consult your dentist before making major changes, as fluoride does have important oral health benefits that should be considered.
References
- Study: Fluoride exposure and duration and quality of sleep in a Canadian population-based sample
- Authors: Jasmyn E. A. Cunningham et al. (2021)
