The silent burden: Noise pollution and mental health in low- and middle-income countries

Sir,

We want to bring your attention to an emerging topic of relevance in mental health, which is the impact of noise pollution, particularly in low- and middle-income countries (LMICs). Noise pollution is defined as ‘unwanted or disturbing sounds’. ¹ The recommended World Health Organisation (WHO) levels of average noise exposure are <53 decibels (dB) for road traffic noise, <54 dB for railway noise, and <45 dB for aircraft noise. ² However, these limits may often be exceeded by average noise levels in urban LMIC settings. ³ The impact of noise pollution on hearing and cardiovascular health, especially hypertension, is well established. ¹ A WHO study in Western Europe found that traffic-related noise was responsible for the loss of 1 million healthy life-years. ⁴ However, the association of noise pollution with mental health issues is relatively less studied.

Although noise pollution is a global health concern, it may disproportionately affect LMICs due to rising industrialisation, urbanisation, and disparity between the burden and resources to address this impact.^5,6 In a systematic review of studies from LMICs, which included 58 studies, it was found that the majority (52%) reported mean noise exposure levels between 60 and 80 dB. ³ Among the major health outcomes assessed in these studies (noise annoyance, cardiovascular health, and mental health) strongest evidence was found for annoyance, whereas data for mental health were inconsistent. ³ We noted that these inconsistencies may be due to cross-sectional designs and limited use of validated psychiatric assessments. However, evidence from non-LMICs suggests a considerable impact of noise on mental health issues.^7,8

Another cohort study involving 9065 participants from Britain reported that exposure to higher noise pollution in childhood and adolescence was significantly associated with increased odds of anxiety. ⁷ Furthermore, 13,401 participants studied found that residential road traffic noise was associated with increased odds of having probable depression (odds ratio = 1.17), ⁹ and in another cohort study, both traffic-related and railway noise were found to be associated with increased risk of Alzheimer's disease (hazard ratio = 1.16). ⁸ An association of higher noise levels with later bedtimes, particularly weekend nights (0.65 h), was found among urban adolescents. ¹⁰ Further, road traffic noise exposure at school was associated with slower complex working memory development (estimated effect β = −3.92) and poorer attention (estimated effect β = 4.22). ¹¹

In LMICs, these risks may be increased by additional stressors such as overcrowding, limited access to mental healthcare, and poor urban planning.

Various strategies to mitigate the effects of noise pollution are mentioned in the literature relevant to richer countries. ¹² Regular monitoring of noise levels and policy measures to ensure compliance with international noise guidelines should, however, be enforced by government agencies. Apart from these measures, recommendations such as economic incentives or taxation, economic restructuring, and the formation of special institutions for training and information have been mentioned, among others. ⁶

Although policies for the control of noise pollution exist in LMICs, various challenges arise in the implementation of these policies. Governments have a low priority for the implementation and enforcement of noise pollution policies. ⁶ Moreover, there is a lack of integration and coordination among various government agencies. There is also a lack of standards and guidelines for the monitoring and control of noise pollution. Also, corruption and poor allocation of funds remain among the crucial challenges for noise pollution control in LMICs. ⁶ This assumes even more importance for mental health, which is under low priority in LMICs, owing to low budgetary allocations, with an average of 0.5% of total health budget compared to 5.1% in high-income countries. ¹³ The combination of low priority for control of noise pollution and overall lack of priority for mental health in LMICs indicates the impact of noise pollution on mental health in these countries is poorly appreciated. There is a need for increased budgetary allocations and stronger policy implementation for noise control measures and the enhancement of mental health services, which are designed to address the impact of noise pollution.^6,13

Clinicians should include an assessment of exposure to noise pollution and information about the residential backgrounds of patients (such as living near highways, airports, and industrial areas) as a part of psychiatric history. Moreover, patients presenting to hospitals with physical health concerns due to noise pollution should also be screened for mental health issues using standardised screening tools, and in case of the presence of such issues, should be referred to mental health experts. Future studies with rigorous methodology are needed to assess the aetiopathogenesis and impact of noise pollution on mental health, and on the effectiveness of strategies aimed at reducing its effects. As data from LMICs are particularly lacking and inconsistent, and most studies are cross-sectional, future studies are warranted from these regions, especially those including longitudinal designs, for a better understanding of this association. ³