Table 2.

Studies on direct-to-consumer hearing devices

Study	Publication type	Aim/design	Key findings and observations
Electroacoustic characteristics
Cheng and McPherson24	Peer-reviewed journal	Examined the amplification characteristics of ten low-cost (≤US $65) OTC devices	Performance of majority of OTC devices was within ANSI standard limit for typical HA, although some were outside the limit for EIN and THD. Overall, OTC devices were low-gain hearing devices with little-to-no-high frequency output.
		This laboratory study used ANSI S3.22 standard for test box assessments and real-ear measurements on ten normal hearing adults	Devices deemed unable to meet needs of the majority of older adults with presbycusis who are likely the more common OTC device users. Researchers suggested that only patients with mild-to-moderate low-frequency reverse sloping HLs (eg, early Meniere’s disease or otosclerosis) may benefit from use.
Callaway and Punch25	Peer-reviewed journal	Aimed to determine the appropriateness of eleven OTC devices (two low cost [,US $100] and eight mid cost [US $100–500]) for mild-to-moderate high-frequency HL, moderate-to- moderately severe sloping HL, and flat moderate HL	Reference test and FOG values were the same for each of the eleven OTC devices. Any volume control position below full-on volume could not produce gain at least 17 dB below OSPL90. Gain across nine of the devices was focused on low-frequency regions. Low-range and mid-range devices varied greatly.
		Descriptive technical study. Laboratory ANSI S3.22 standard test box assessments performed twice, 2 months apart. Test–retest <5 dB for all measurements in eight OTC devices	Mid-range OTC devices met the gain and output targets to a greater extent than the low-range devices. In addition, low-range devices had high EIN, which may result in safety hazard. Hence, low-range OTC devices appear to be electroacoustically inadequate, whereas mid-range devices appear to potentially be useful for people with mild-to-moderate HL.
Chan and McPherson26	Peer-reviewed journal	Follow-up study to determine if the amplification characteristics of low-cost (≤US $115) OTC device have changed over a decade	Electroacoustic characteristics of OTC devices were similar to their earlier study performed over 10 years prior (ie, Cheng and McPherson24).
		Laboratory ANSI S3.22-2009 standards were used for test box assessments and real-ear measurements on a simulated condition using a KEMAR	Some of the OTC devices were able to match the target gains in simulated conditions, although authors suggest that the factors such as ineffective volume control function, high internal noise, and irregular frequency response may limit the potential benefit to people with HL.
Smith et al17	Peer-reviewed magazine	Evaluated low-end and high-end PSAPs and HAs amplification characteristics	All high-end HAs were able to fit most HL configurations, whereas two high-end PSAPs and one app were able to meet the moderate HL configuration.
		Laboratory ANSI S3.22-2009 standards were used for test box assessments and real-ear measurements on a simulated condition using a KEMAR	Most low-end HAs and PSAPs produced inappropriately high gain at low frequencies, whereas high-end devices produced appropriate amplification for moderate HL configurations. Low-end PSAPs and HAs were found to be inappropriate for any severity and configuration of high-frequency HL.
Survey of consumers
Kochkin27	Peer-reviewed magazine	Aimed at estimating the population of PHL who use direct-mail HAs and PSAPs and also to compare the characteristics of those who use one-size-fits-all products with those who use custom HAs	Estimates suggested that about 3.3% of the HA owners received their device through direct-mail orders. PSAP owners were found to be 4.8% of the non-adopters population. PSAP owners paid less than US $50 for their device when compared to direct-mail HA owners who paid a median of US $237.
		Used a cross-sectional survey design and consisted sample of 3174 HA owners and 4339 non-adopters of HAs	Direct-mail and PSAP owners earned US $10,000 less per year, were less likely to buy binaural HAs, and used devices less (ie, 3 hours a day when compared to 10 hours a day) than those who purchased custom HAs.
			Nearly 75% of direct-mail and PSAP owners were candidates for custom HAs, although estimates suggested that <18% users substitute PSAPs for custom HAs.
Kochkin31	Peer-reviewed magazine	Compared the consumer satisfaction, subjective benefit, and quality-of-life changes associated with traditional and direct-mail HAs	Nearly half (45%) of direct-mail HA consumers have previously tried or owned traditional HAs and have HL profile that is not dissimilar to typical HA user.
		The study used a cross-sectional survey design. Sample included 1,721 traditional HA owners and 2,332 direct-mail HA owners	Direct-mail HA owners are older, are more likely to be retired, have lower income, more experienced HA user, and more likely to use one HA when compared to traditional HA owners.
			Consumers believe that both direct-mail and traditional HAs provide equal benefit resulting in higher perceived value. Direct-mail users are more positive towards their device. Direct-mail HAs provided about average benefit, but significantly less real-world benefit than HAs dispensed by those with professionals who adhere to highest levels of best practice. However, consumers were willing to make trade-offs in benefit for substantial cost reduction.
Consumer Electronic Association28	Consumer survey report	Market research aimed at exploring the various situations in which PSAP users benefit from useage	Only a fraction of those diagnosed with HL (6%) and those with at least some trouble hearing (4%) own PSAPs, although two out of five are interested in purchasing direct-to-consumer hearing devices.
		Study used a cross-sectional Internet-based survey design and included a national sample of 3,459 US adults who had at least little trouble hearing	Although most consumers with trouble hearing would consult hearing care professional, few were interested in seeking information online (14%), from friends and family (13%), and others with hearing difficulties (10%). More than two-thirds of the sample preferred purchasing nonprescription hearing devices (ie, mail or drug stores). Current PSAP owners mainly used them for listening to TV, although potential buyers were interested in exploring its use for wider situations.
JapanTrak29	Consumer survey report	Aimed at understanding the HL prevalence rates and HA adoption rates. Also explored hearing device usage and demographics	HL prevalence in representative sample was 10.9%, and 14.1% of PHL have HAs with more severe degree of HL indicated higher adoption rates.
		Market survey designed and executed by Anovum (Zurich) on behalf of Japan Hearing Instruments Manufacturers Association Representative sample of 15,036 with 1,348 having HL (of which 450 were HA owners)	14% from direct-mail or online, 18% of HA owners purchased from an optical shop, and 56% from hearing health care professional.
JapanTrak30	Consumer survey report	Aimed at understanding the HL prevalence rates and HA adoption rates. Also explored hearing device usage and demographics	HL prevalence in representative sample was 11.3% PHL, and 13.5% having HAs and use of HAs resulted in significant improvement in quality of life.
		Representative sample of 14,316 with 1,306 having HL (of which 416 were HA owners)	19% from direct-mail or online, 14% of HA owners purchased it from an optical shop, and 49% from hearing health care professional.
			Satisfaction with HAs purchased online is lower than purchased in HA centers.
Outcome evaluation
McPherson and Wong32	Peer-reviewed journal	Studied differences in self-reported benefit between conventional HAs and OTC devices	No significant differences in self-reported benefit scores between device types.
		Prospective open trial 19 older (63–83 years) adults with mild-to-moderate HL	Concluded that affordable, OTC devices provide a potential opportunity for greater numbers of PHL to access amplification and benefit from improved communicative abilities.
Sacco et al33	Peer-reviewed journal	Studied the clinical value of OTC devices	Use of OTC devices resulted in improvement in various domains of hearing in quiet and noisy situations, improved communication, and decreased negative emotions.
		Prospective open trial	Acceptability of the device was low to moderate.
		31 older (60+) adults with mild-to-moderate HL	Concluded that TEO First® is an effective OTC device that improved patients’ quality of life.
Xu et al34	Conference paper	Examined the preferences of PSAPs and HAs via listening to different sounds processed by these devices	In laboratory settings, PSAPs performed as well as HAs for everyday noises and music.
		Cross-sectional comparison study conducted in a laboratory	HAs were significantly more preferred than PSAPs for speech.
		23 adults (23–83 years) with mild-to-moderate HL	Different devices process some types of sounds more effectively than other types of sounds.
Tedeschi and Kihm35	Peer-reviewed magazine	Pilot study examined the outcome of direct-to-consumer hearing devices with and without professional guidance	Some of the participants (13%) were not able to self-identify the red-flag conditions that would require medical consultation, nearly half were not able to correctly self-assess the degree of loss, and nearly a third of the participants with moderate loss could have delayed seeking help with professionals.
		29 older people (aged 60 or older) with mild-to-moderate HL who used PSAPs and provided outcome data through survey after 3 and 6 weeks	Individuals supported by hearing health care professionals experienced better outcomes in terms of various indicators, which include daily usage, expectations, overall satisfaction, usage, willingness to recommend, and perceived success.

Abbreviations: OTC, over-the-counter; ANSI, American National Standard Institute; HA, hearing aid; EIN, equivalent input noise; THD, total harmonic distortion; HL, hearing loss; FOG, full-on gain; OSPL90, output sound pressure level for 90-dB input sound pressure level; KEMAR, Knowles Electronics Mannequin for Acoustic Research; PSAP, personal sound amplification product; PHL, people with hearing loss.