Longitudinal observational study with 12-month follow-up using a self-reported questionnaire and objective assessment of posture while texting on a smartphone using inclinometer measure at baseline. The follow-up evaluation was carried out after one year through telephone contact, via e-mail, or social networks. This study followed the recommendations of the STROBE Guidelines – Strengthening the Reporting of Observational Studies in Epidemiology.16 The funders played no role in the design, conduct, or reporting of this study.

The sample consisted of 457 volunteers without neck pain, aged between 18 and 65 years of both sexes. Data were collected by researchers in a tent located in a busy area of ​​the Augusto Motta University Center in Rio de Janeiro from November 2018 to November 2019. Participants were invited to participate through advertising boards next to the evaluation tent.

At baseline, a questionnaire was applied containing identification of the research participant with sociodemographic (name, age, and sex) and anthropometric (weight and height) questions. To exclude participants with neck pain at baseline, they were asked: “Do you have neck pain today?” the answer options were: “Yes” or “No”. The amount of time the participant is exposed to smartphone use was assessed through the question, “On a typical weekday, how many hours a day do you spend reading, texting, and playing games on your smartphone?” with nine answer options, the first of which began with, “I only use my smartphone to talk”, and then the answers varied according to the time spent using the smartphone from, “<1 hour per day”, to, “About 7 or more hours per day”. Regarding concerns about their postures, we asked, “Do you worry about your body posture?”, “Do you think your posture is adequate when typing on your smartphone?”, and, “Do you worry about your posture on your smartphone when typing?”, the response options were, “very often”, “often”, “once in a while”, “rarely”, or “never”. We also evaluated visual problems, as the individual's posture can be altered due to the fact that they have compromised visual acuity without the necessary corrections, so we asked, “Do you have vision problems?”, with the answer options, “Yes”, or, “No” and also, “Do you have vision problems and do you wear glasses (or contact lenses)?”, the answer options were, “Yes”, “No” or, “I use them, but I forgot”.

Lifestyle was assessed with questions about physical activity, smoking, sleep quality, and dependence on smartphone use. The short version of the International Physical Activity Questionnaire (IPAQ) assessed the level, weekly frequency, and daily workload of activities, classifying the individual as: sedentary, insufficiently active, active, or very active.17 Smoking was assessed using the question “In the last 30 days, how many days did you smoke cigarettes?” with eight response options ranging from, “I never smoked”, to, “Every day in the last 30 days”. Sleep quality was assessed with the question: “Did you have trouble sleeping in the last month?” with four response options: “none”, “a little”, “some”, or “serious”. Furthermore, the questionnaire also included the Smartphone Addiction Scale18 and psychosocial factors such as anxiety, depression, social isolation, and stress.19

Text neck was assessed by measuring the flexion angle of the cervical spine, with the assumption that the greater the cervical flexion angle, the greater the text neck. It was measured while typing on the smartphone using an inclinometer (CROM – Cervical Range of Motion). The reliability and validity of the CROM were established by Capuano-Pucci20 and Tousignant,21 respectively. The CROM measures cervical range of motion for flexion and extension, lateral flexion, and rotation using three separate inclinometers, each in a sagittal, frontal, and transverse plane, respectively. We only assessed the cervical flexion degree. The participant was instructed to stand on a cross marked on the floor. In the upright position, the CROM device was placed as if putting on a pair of glasses. The participant was asked to send a text message to someone via their smartphone, simulating daily use. The cervical angle measurement with the CROM inclinometer was recorded with the participant in an orthostatic and seated position (Fig. 1). The evaluator was blind to the participants' responses regarding NP results.

Fig. 1.

The measure of cervical flexion angle using the CROM device while the participant was texting on the smartphone. The left participant yielded a cervical flexion angle of 4° and the right one 50°.

The one-year follow-up was carried out by telephone call or text message and included only questions regarding the complaint of neck pain and the frequency of neck pain: “Do you have neck pain today?” The answer options were: “Yes” or “No” and frequency of neck pain: “How often have you had neck pain?” The response options were: “Very often”, “Often”, “Once in a while”, “Rarely”, or “Never”. These responses were dichotomized for regression analysis into 1 – Never and Rarely, and 2 – Occasionally, Often, and Very often.

This study required a minimum sample size of 430 participants to provide a power of 80 % and an alpha of 5 %, considering a prevalence of 16 % of neck pain in the exposed group and 6 % of neck pain in the non-exposed group at the one-year follow-up.22 Based on the study of Damasceno et al. ,23 the percentage of participants exposed to text neck was 40 %. The estimated sample size also allowed a limit of 15 % loss of follow-up.

All analyzes were performed using version 0.99.486. from RStudio (https://posit.co). Participant characteristics were described using proportions, means, and standard deviations. Four logistic regression models were carried out. The two first evaluated standing text neck, psychosocial variables (anxiety and depression), and lifestyle variables (level of physical activity and quality of sleep) as independent variables with prevalence of neck pain and frequency of neck pain as dependent variables, respectively. The two second ones evaluated sitting text neck and the same psychosocial and lifestyle variables as independent variables with the same dependent variables. Potential confounders, including age, sex, time using the device, and smartphone dependence, were included in the logistic regression models according to what the literature describes as potential risk factors for neck pain and variables related to smartphone use. The significance level adopted in the study was 5 %.

Some strengths of the study are the longitudinal design with 12-month follow-up, along with the potential biopsychosocial confounding factors included in the analysis. The main limitation of this study was the failure to differentiate between acute and chronic stages of NP. Additionally, we used a single question regarding pain on the day of the one-year follow-up. We chose this question because it is the least influenced by memory and covers acute and chronic neck pain. Although our age range was 18 to 65 years, the average age was relatively young (27 years). It is also important to highlight that the monitoring period for the participants took place during the COVID-19 pandemic in 2020, possibly leaving people to be more sedentary. The question of whether participants start to adopt a better posture after experiencing neck pain (NP) was addressed with our longitudinal design. However, it remains unknown whether the neck posture participants adopted during the study task is significantly different from their habitual posture when texting on a smartphone.

This 12-month longitudinal study contributes to the existing literature on the topic by reinforcing that text neck is not a risk factor for NP. Other factors such as sleep quality and level of physical activity seem to be more relevant. These results challenge the belief that flexed neck posture during smartphone use leads to NP. This linear causal relationship reasoning based solely on injuries or structural changes to justify pain is outdated. Future studies should investigate the influence of smartphone use before sleep on neck pain, as well as whether text neck increases the risk of neck pain in older adults.