Posted on December 1, 2014 by in Sleep Science

    All medical authorities agree that sufficient amounts of good quality sleep are fundamental to maintaining physical health and mental well-being. Numerous clinical studies have attested to the importance of the ambient sleeping temperature to the quality and length of sleep enjoyed. However, rather than heating or cooling the room to impact the temperature experienced by the sleeper, a much more fundamental approach is to heat or cool the mattress itself. This is the method employed by the ChiliPad™ Cube 1.1 cooling and heating temperature control system, a mattress pad that regulates mattress surface temperatures by actively circulating water through a network of micro-silicone tubes at temperatures that can be set in a range as low as 46° F to over 118° F

    As might be expected based on everyday experience, there is a high degree of variability in what different individuals consider to be an optimum temperature for excellent sleep. Some of us sleep better in warmer conditions, while others prefer a much cooler environment. For most couples, this means a certain amount of compromise in sleeping temperature is inevitable. However, ChiliPad offers an alternative to this typically no-win, lose-lose situation with a Dual Zone design that provides individualized regulation of sleeping temperature year-round.

    The Woodlands Sleep Evaluation Center, a Sleep Disorders Center in The Woodlands, Texas, directed by David W. Michalak, M.D. and W. David Brown, Ph.D., recently conducted an “openlabel” test of the ChiliPad product with 10 couples, meaning that the study was un-blinded and the participants knew that they were sleeping on a ChiliPad mattress pad. Participants were selected who expressed willingness to fill out daily questionnaires regarding the quality and length of their sleep the previous night on their regular mattress for seven days as a baseline, followed by seven nights while using the ChiliPad product. Bed partner couples were chosen not only to maximize the number of participants in the study, but also to exploit the ability of the product to independently adjust the temperature for each side of the bed. All participants were volunteers and were not financially compensated for participating in the study.

    Once identified, participants were sent the first 7 days of questionnaires, one for each day. Every morning, each participant would fill out a single-page form that asked questions offering numerically-scaled responses regarding the quality and quantity of their sleeping experience for the previous night on their current mattress. These included questions regarding the overall quality of sleep, how long they thought that it took them to get to sleep (sleep onset latency), how well they felt upon awakening, how alert they felt later in the day, even how effectively they recalled their dreams. A number of other questions were asked (how many times they awoke during the night, or whether they felt too hot or too cold) that were later used to combine with measures of overall sleep quality in preparing a statistically rigorous “Sleep Quality Composite score”.

    No physical measurements of actual sleep onset latency or total sleep time were made in the study; the self-reported responses were purely subjective. While ChiliPad plans further studies that will involve objective measurements of sleep onset latency and total sleep time, the results of subjective studies of sleep experiences are important, being that most of us care about how we feel about our sleep experience, not what some measuring device might tell us about how we should feel.

    After the first 7 days of the study were completed, responses to the baseline questionnaires were sent back to the sleep center in an attempt to not remind the participants of their scores on the pre-treatment questionnaires. Next, each couple was sent either a ChiliPad queen-size or king-size dual-zoned unit and were allowed to set whatever temperature either of them thought they would prefer. The study did not track the actual temperatures used or how participants might have changed them over the course of the study. The couples used the ChiliPad mattress pad for 7 days, answering the same questions each morning as they had done in establishing a baseline for the study.

    Of the 20 participants who began the study, 19 finished, a 95% rate of completion. Based on a review of the results comparing the responses with and without the ChiliPad overlay, the product was a roaring success with the study group. It bears repeating that the participants were not compensated for their participation in the study. Here is a review of the study’s results with 7 days of scores with and without the ChiliPad mattress pad averaged separately:

    Overall Sleep Quality

    When asked to rate the quality of their sleep on the ChiliPad mattress versus their own mattress on a 5-point scale where 1 was “terrible” and 5 was “excellent,” the average scores of 14 of 19 participants, or about 75%, indicated that they got a better quality of sleep on the ChiliPad compared to their regular mattress.

    Felt Upon Awakening

    Based on a 5-point scale for how they felt upon awakening where 1 was “exhausted’ and 5 was “wide awake,” the average scores of 15 out of the 19 participants, or about 80%, indicated that they felt better upon awakening after sleeping on the ChiliPad than after sleeping on their own mattress.

    Level of Alertness

    On a question with a 5-point response that was answered later each day regarding their subjective levels of alertness where 1 was “falling asleep” and 5 was “energetic,” the average scores of 15 out of 19 participants, or about 80%, indicated that they felt more alert after a night’s sleep using the ChiliPad mattress overlay than after sleeping on their own mattress.

    Total Sleep Time

    In terms of total sleep time, average scores of nearly two-thirds of the participants (12 out of 19) indicated that they slept longer on the ChiliPad unit than on their own mattress.

    Sleep Latency

    Over half of the participants reported that they thought they got to sleep quicker on ChiliPad and by a larger margin (in minutes) than those who said that it took longer to get to sleep. The data here was amenable to a more rigorous statistical analysis, revealing that the results were statistically significant for a decrease in subjective sleep onset latency in the ChiliPad arm of the study at a statistical power of ≤0.05.


    An attempt was made to introduce a measure for detecting the occurrence of REM (rapid eye movement) sleep by including a question on whether participants felt that they had had more, less, or the same quantity of dreams during the previous night. Over twice as many participants reported dreaming more (recalling more dreams) on the ChiliPad mattress versus those who said they dreamt more on their own mattress.

    Sleep Quality Composite Score

    To minimize the possibility of any of the multiple variables that were measured to generate significant changes simply by chance, a “Sleep Quality Composite Score” for overall subjective sleep quality was also calculated. The Score combined Overall Sleep Quality and Felt Upon Awakening scores with reported feelings of being too hot or too cold, as well as how many times a participant recalled waking up at night into a single score. A Wilcoxon paired signed rank test was used to compare and establish the statistical significance of the two sets of data from the pre-treatment and treatment weeks. According to the independent firm that conducted the statistical analysis, “Using the Sleep Quality Composite Score, the results are significant at a statistical power of 0.05 for improved subjective sleep quality in the ChiliPad arm of the study.”


    In this unbiased study assessing the subjective, self-reported reactions of participants to sleeping with or without the ChiliPad mattress overlay for 7 days, the ChiliPad product clearly demonstrated its superiority compared with a conventional mattress and conventional modulation of sleeping temperature. ChiliPad looks forward to publishing data from continued investigations into the clinical utility of this highly effective sleep aid.