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. 2022 May 2;5(5):e2211958.
doi: 10.1001/jamanetworkopen.2022.11958.

Estimating the Burden of Influenza-like Illness on Daily Activity at the Population Scale Using Commercial Wearable Sensors

Aziz Mezlini  1 , Allison Shapiro  1 , Eric J Daza  1 , Eamon Caddigan  1 , Ernesto Ramirez  1 , Tim Althoff  2 , Luca Foschini  1
Affiliations

Estimating the Burden of Influenza-like Illness on Daily Activity at the Population Scale Using Commercial Wearable Sensors

Aziz Mezlini et al. JAMA Netw Open. .

Abstract

Importance: The severity of viral infections can vary widely, from asymptomatic cases to complications leading to hospitalizations and death. Milder cases, despite being more prevalent, often go undocumented, and their public health burden is not accurately estimated.

Objective: To estimate the true burden of influenza-like illness (ILI) in the US population using a surrogate measure of daily steps lost as measured by commercial wearable sensors.

Design, setting, and participants: This cohort study modeled data from 15 122 US adults who reported ILI symptoms during the 2018-2019 influenza season (before the COVID-19 pandemic) and who had a sufficient density of wearable sensor data at symptom onset. Participants' minute-level step data as measured by commercial wearable sensors were collected from October 1, 2018, through June 30, 2019. Minute-level activity time series were transformed into day-level time series per user, indicating the total number of steps daily.

Main outcomes and measures: The primary end point was the number of steps lost during the period of 4 days before symptom onset (the latent phase) through 11 days after symptom onset (the symptomatic phase). The association between covariates and steps lost during this interval was also examined.

Results: Of the 15 122 participants in this study, 13 108 (86.7%) were women, and the median age was 32 years (IQR, 27-38 years). For their ILI event, 2836 of 15 080 participants (18.8%) sought medical attention, and only 61 (0.4%) were hospitalized. Over the course of an ILI lasting 10 days, the mean cumulative loss was 4437 steps (95% CI, 4143-4731 steps). After weighting, there was an estimated overall nationwide reduction in mobility equivalent to 255.2 billion steps (95% CI, 232.9-277.6 billion steps) lost because of ILI symptoms during the study period. This finding reflects significant changes in routines, mobility, and employment and is equivalent to 15% of the active US population becoming completely immobilized for 1 day. Moreover, 60.6% of this reduction in steps (154.6 billion steps [95% CI, 138.1-171.2 billion steps]) occurred among persons who sought no medical care. Age and educational level were positively associated with steps lost.

Conclusions and relevance: These findings suggest that most of the burden of ILI in this study would have been invisible to health care and public health reporting systems. This approach has applications for public health, health care, and clinical research, from estimating costs of lost productivity at population scale, to measuring effectiveness of anti-ILI treatments, to monitoring recovery after acute viral syndromes such as during long COVID-19.

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Conflict of interest statement

Conflict of Interest Disclosures: Drs Mezlini, Shapiro, Daza, Caddigan, Ramirez, and Foschini are employees of Evidation Health Inc, developer of the Achievement health and research platform. No other disclosures were reported.

Figures

Figure 1.
Figure 1.. Overview of Data Collection and Analysis
ID indicates identification; and ILI, influenza-like illness.
Figure 2.
Figure 2.. Mean Step Differentials and Histogram of Total Influenza-Like Illness (ILI) Burden Across Participants Measured in Lost Steps
A, Mean step differentials during ILI events and matched control periods. The step differentials are the mean across participants of the per-participant difference between the estimated counterfactual step counts and the observed step counts. Shaded areas indicate SE above and below the line. B, Total steps lost during days 0 to 10 during ILI events and matched control periods.
Figure 3.
Figure 3.. Association of Confounder Variables With the Mean Step Differentials
Shaded areas indicate SE for each group. GED indicates General Educational Development certification; and ILI, influenza-like illness.
Figure 4.
Figure 4.. Mean Step Differentials Between Participants With Influenza-like Illness (ILI) and Controls by Symptom Experienced
Shaded areas indicate SE for each group.
See this image and copyright information in PMC

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