Why More Data Is Not Always Better

The idea

Wearables, apps and home tests can produce more numbers every day than most people (or clinicians) can interpret. It is natural to assume that more data means better decisions. Research suggests the picture is more mixed. This page is information only and does not recommend that you start, stop or change tracking.

Evidence labels used here: established, promising but limited, mixed, insufficient evidence, commentary (an expert opinion article, not a study).

Four ways extra data can mislead

1. Noise. Consumer devices estimate many things, and each estimate carries error. More estimates mean more noise, not necessarily more signal.
2. False patterns. The more relationships you look at, and the less you chose them in advance, the less likely any one "finding" is to be true. [1] Research quality is not the same as a dashboard, but the arithmetic is the same.
3. Natural fluctuation. Unusually high or low days tend to be followed by more ordinary ones, which can look like change. [2] See Baseline Variation and Normal Fluctuation.
4. Burden. An expert commentary in npj Digital Medicine says excess monitoring may contribute to fatigue, anxiety and information overload, sometimes reducing engagement and worsening outcomes. [3] This is commentary, not a trial.

What trials of wearables have found

Activity. An umbrella review of 39 systematic reviews (98 original studies, mostly randomized trials) found that interventions using wrist-worn trackers increased physical activity in diverse populations. Effects on cardiometabolic risk markers, quality of life, depression or anxiety, and pain were limited and inconsistent, and most of the reviews were rated low confidence. [4] Label: promising but limited for activity, mixed for other outcomes.

Weight loss. In a randomized trial of 471 adults aged 18 to 35 with a BMI of 25 to under 40, adding a wearable device to a standard behavioral program resulted in less weight loss over 24 months (3.5 kg) than the standard program alone (5.9 kg). The authors concluded that feedback devices may not offer an advantage over standard approaches. [5] This is one trial in one age group, so it does not show that all devices fail. Label: mixed.

Mental effects in people with heart disease. A review of consumer wearables in people with cardiovascular disease found that the devices can motivate some people but provoke adverse psychological reactions in others. [6] A scoping review of 110 publications described health anxiety, repeated reassurance seeking, and excessive self-monitoring in some patients, and noted that evidence is limited. [7]

Accuracy is not benefit

Even a very accurate sensor tells you what happened, not what to do about it. Measuring something more often does not make it change. Whether a tracker is accurate and whether using it improves health are two separate questions, and the second needs trials like the ones above.

A simple way to decide how much to track

• Start from a question you care about, such as "am I getting enough sleep?" rather than from the device.
• Pick one or two measures that answer it, and ignore the rest.
• Notice whether tracking makes you calmer, more worried, or more fixated. If numbers are causing distress, see Tracking Anxiety and Compulsive Measurement.
• Remember that how you feel, what you can do, and what a clinician finds on examination matter more than a proprietary score. See What Counts as a Meaningful Outcome?.

Who should be especially cautious

Reviews in people with heart disease describe health anxiety and repeated reassurance seeking in some patients. [7][6] People with a history of an eating disorder face separate concerns; see When Not to Experiment. Talk with your own clinician about whether and how to track.