Philips Actiwatch Discontinued? Here Are the Top Research-Grade Replacements Available Now

1. Introduction

The Philips Actiwatch Spectrum has long been a trusted tool for researchers studying sleep patterns, circadian rhythms, and activity cycles. However, with the Actiwatch Spectrum now discontinued, many researchers and institutions are left searching for reliable alternatives that match or exceed its capabilities.

While there are several actigraphy devices on the market, not all meet the rigorous standards required for research-grade sleep and circadian studies. For those seeking validated devices that provide detailed, multi-dimensional data—including light exposure, movement, and temperature—only a select few devices truly stand out.

In this guide, we will highlight the top scientifically validated replacements available today, focusing on devices that offer the critical feature of multi-spectral light sensing—a necessity for high-quality circadian research.

2. Why Most Actigraphy Devices Fall Short as Actiwatch Replacements

Although there are numerous commercial actigraphy devices available, many fall short when used as replacements for the Philips Actiwatch Spectrum. Here’s why:

• Lack of Spectral Light Sensing: Many actigraphy devices only include basic photopic light sensors, which measure overall light intensity but fail to differentiate between key light wavelengths like blue, infrared, or ultraviolet light. Devices such as GENEActiv, ActiGraph wGT3X-BT, and MotionWatch 8 fall into this category. For researchers studying light’s impact on circadian rhythms, particularly the effects of specific wavelengths (e.g., blue light suppression of melatonin), this lack of spectral resolution is a serious limitation.
• No Flicker Reduction: Another issue with standard light sensors is their inability to filter out 50/60 Hz flicker, commonly produced by artificial lighting sources like LEDs and fluorescent lights. Without flicker reduction, light data can be unstable and unreliable, particularly in real-world environments.
• Missing Skin Temperature Monitoring and Event Marker: Additionally, several widely used devices do not offer skin-contact temperature sensors or event marker buttons. Skin temperature is a valuable physiological marker for circadian phase assessment, and event markers allow participants to log key events (like lights off or awakenings), improving data richness. The absence of these features limits the device’s usefulness in detailed, nuanced research settings.

Because of these limitations, the following two devices rise above the rest as the only true research-grade replacements for the Actiwatch Spectrum—providing validated accuracy, advanced sensor technology, and full flexibility for serious researchers.

3. Top Research-Grade Replacements for Philips Actiwatch Spectrum

3.1 Fibion Krono: The Most Advanced Multi-Sensor Actigraphy Replacement

The Fibion Krono is a leading-edge actigraphy device designed to deliver detailed, high-precision data across multiple physiological and environmental domains. It offers a comprehensive solution for researchers who require robust, validated data in sleep and circadian studies.

1. Multi-Spectral Light Sensors:
   One of Krono’s standout features is its multi-spectral light sensing capability, measuring blue light (460–490 nm), photopic light, and infrared light separately. This level of detail allows researchers to assess both natural and artificial light sources and their impact on circadian rhythms. In addition, the device includes 50/60 Hz flicker reduction, ensuring stable, reliable light readings even under artificial lighting conditions—something lacking in most other devices.
2. High-Precision Accelerometry: The Krono is equipped with a triaxial accelerometer (±2 g range, 0.001 g sensitivity), offering precise movement tracking essential for analyzing sleep-wake patterns, physical activity, and circadian cycles.

1. Large Skin-Contact Temperature Sensor: Another critical advantage is the inclusion of a large, skin-contact temperature sensor with ±0.1°C accuracy. Unlike devices where the sensor may record ambient temperature, the Krono ensures accurate wrist skin temperature monitoring—a key circadian phase marker. Importantly, this sensor also serves as an effective off-wrist detection tool; when the device is removed, the drop in skin temperature is immediately detectable, improving data validity.
2. Event Marker Button & Validation: The device includes an event marker button, allowing participants to log key events, which can later be correlated with objective data. The Krono has been scientifically validated, including studies comparing its outputs to gold-standard polysomnography (PSG) and use in clinical research environments.
3. Data Access: Researchers have access to raw data exports for all collected parameters, enabling customized analyses and advanced statistical evaluations.

3.2 Condor ActTrust 2: Multi-Spectral Light Measurement Alternative

The Condor ActTrust 2 is another strong contender for replacing the Actiwatch Spectrum, particularly for studies where light exposure measurement is a priority. It features an array of independent light sensors measuring red, green, blue (RGB), infrared, and ultraviolet (UV) channels—offering detailed light spectrum analysis.

1. Temperature Monitoring: The ActTrust 2 includes dual thermistors, which record both skin and ambient temperature. While this setup provides useful temperature data, the accuracy of the skin temperature reading may vary depending on how securely the device is worn and environmental factors.
2. Accelerometry & Event Marker: It comes with a 2-axis accelerometer by default, with the option to upgrade to a 3-axis configuration. The device also includes an event marker button, allowing for participant interaction.
3. Validation: ActTrust 2 has been validated in clinical and research settings, ensuring data accuracy for circadian and sleep studies.

4. Which Actiwatch Replacement Should You Choose?

While both the Fibion Krono and Condor ActTrust 2 offer multi-spectral light sensing and research-grade validation, the Fibion Krono stands out as the most comprehensive alternative in most cases. Its advanced sensor suite, combined with participant-friendly features and scientific validation, makes it the preferred choice for researchers needing detailed, reliable circadian and sleep data.

Why Fibion Krono is the Best Replacement Option:

• Multi-spectral light measurement (Blue, Photopic, Infrared) with 50/60 Hz flicker reduction:
  Ensures stable, accurate light readings, crucial for circadian studies, especially under varying lighting conditions.
• High-accuracy, large skin-contact temperature sensor: Provides true wrist skin temperature data, not ambient readings, enhancing circadian phase analysis.
• Temperature sensor also used for off-wrist detection: Automatically detects when the device is removed based on a temperature drop, improving data integrity.
• Triaxial accelerometer for precise movement tracking: Captures high-resolution activity data, essential for sleep-wake pattern analysis.
• Event marker button for participant interaction: Enables participants to log important events, enhancing the contextual accuracy of collected data.
• Scientifically validated in clinical and research settings: Tested against gold-standard methods like polysomnography (PSG), ensuring reliable outputs.
• Raw data export: Offers full flexibility for custom analysis and advanced research needs.

While the Condor ActTrust 2 remains a solid option for those prioritizing multi-spectral light sensing with straightforward usability, it lacks some of the precision and advanced features offered by Fibion Krono, particularly in temperature accuracy and flicker reduction.

5. Conclusion

The discontinuation of the Philips Actiwatch Spectrum has left many researchers in need of a validated, reliable alternative. However, not every actigraphy device on the market is suited for high-level research use. After careful evaluation, two devices emerge as the strongest options: the Fibion Krono and the Condor ActTrust 2.

While both offer essential features like multi-spectral light sensing and event marker buttons, the Fibion Krono delivers a more complete, research-grade solution in most cases. Its advanced multi-spectral light sensors with flicker reduction, skin-contact temperature monitoring with off-wrist detection, triaxial accelerometry, and scientific validation make it the best Actiwatch replacement for researchers who demand accuracy, flexibility, and comprehensive circadian data.

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