The Association between Noise, Cortisol and Heart Rate in a Small-Scale Gold Mining Community-A Pilot Study

We performed a cross-sectional pilot study on salivary cortisol, heart rate, and personal noise exposures in a small-scale gold mining village in northeastern Ghana in 2013. Cortisol level changes between morning and evening among participants showed a relatively low decline in cortisol through the day (-1.44 +/- 4.27 nmol/L, n = 18), a pattern consistent with chronic stress. A multiple linear regression, adjusting for age, sex, smoking status, and time between samples indicated a significant increase of 0.25 nmol/L cortisol from afternoon to evening per 1 dBA increase in equivalent continuous noise exposure (L-eq) over that period (95% CI: 0.08-0.42, Adj R-2 = 0.502, n = 17). A mixed effect linear regression model adjusting for age and sex indicated a significant increase of 0.29 heart beats per minute (BPM) for every 1 dB increase in L-eq. Using standard deviations (SDs) as measures of variation, and adjusting for age and sex over the sampling period, we found that a 1 dBA increase in noise variation over time (L-eq SD) was associated with a 0.5 BPM increase in heart rate SD (95% CI: 0.04--0.9, Adj. R-2 = 0.229, n = 16). Noise levels were consistently high, with 24-hour average L-eq exposures ranging from 56.9 to 92.0 dBA, with a mean daily L-eq of 82.2 +/- 7.3 dBA (mean monitoring duration 22.1 +/- 1.9 hours, n = 22). Ninety-five percent of participants had 24-hour average L-eq noise levels over the 70 dBA World health Organization (WHO) guideline level for prevention of hearing loss. These findings suggest that small-scale mining communities may face multiple, potentially additive health risks that are not yet well documented, including hearing loss and cardiovascular effects of stress and noise.