H567/03 Section B Option 3 - Black and Black (2007) and managing stress
Use the prescribed aircraft-noise research to distinguish exposure, reported stress and health, evaluate community evidence and apply an environmental stress-management strategy.
Noise, health and study design
Black and Black (2007), Aircraft noise exposure and resident's stress and hypertension: A public health perspective for airport environmental management, examined whether aircraft noise was associated with chronic stress, health-related quality of life and hypertension. The published paper has four authors: D. A. Black, J. A. Black, T. Issarayangyun and S. E. Samuels; “Black and Black” is the prescribed OCR study label.
Noise can be a continuing demand when it is intrusive, disrupts rest and is outside the resident's control. The biological stress account makes a possible link from exposure through repeated arousal to health. The study investigated community associations; it did not measure the complete SAM/HPA chain or experimentally assign people to noisy homes.
It used a cross-sectional questionnaire comparison between an aircraft-noise-exposed area near Sydney's Kingsford Smith Airport and a control area outside aircraft flight paths. The areas were chosen to be socioeconomically comparable. Noise measurements and a review of airport policy accompanied the survey. Comparing existing residential areas is a naturally occurring exposure comparison, not random assignment of an independent variable. Statistical adjustment for measured covariates cannot automatically remove every difference between areas.
The design allows a relatively large real-community investigation without deliberately exposing people to harmful noise. However, exposure and health reports were assessed at the same general stage, so temporal order and causality remain uncertain. The research connects environmental stress to public health and decisions about an economically important airport.
Sample and measures
The main survey distributed 1,500 questionnaires, intended as 750 in each area, and received 704 completed questionnaires. Participants were aged 15–87. The control area was South Penrith, about 55 km from the airport. The areas were matched at an area level; they did not consist of individually matched pairs. The control group was on average about four years older and had a higher proportion of women, illustrating remaining demographic differences.
Addresses near railways, industry or highways were excluded to reduce other major noise sources. Apartments, commercial premises and properties for sale or lease or appearing abandoned were also excluded. These decisions improve the focus on aircraft exposure but narrow the housing and population represented. Returning a postal questionnaire involves self-selection, so those responding may differ from those not responding.
Health-related quality of life used four selected SF-36 version 2 scales: physical functioning, general health, vitality and mental health. Scores ran from 0 to 100, with higher scores indicating better health on that scale. Reported hypertension was based on a question about diagnosis by a doctor or nurse, rather than a blood-pressure reading taken by the researchers. Noise stress, sensitivity and annoyance were assessed through questionnaire items, including rating scales.
Demographic and lifestyle information included possible confounds such as exercise, smoking, alcohol, diet and family history of hypertension. These measures make adjustment more informative, but unmeasured or inaccurately reported factors can remain. A reported stress score is a subjective outcome, not a cortisol assay.
Survey and noise procedure
A pilot at Kurnell used a distribution of 100 questionnaires. Analysis led to revisions, including deletion of some noise-stress and noise-sensitivity items, before the main survey. Piloting helps identify unsuitable questions; it does not mean that every later item is automatically valid.
The main mailing included a covering letter describing a survey of environmental noise and a return-paid envelope. Avoiding an aircraft-only description was intended to reduce selective participation by residents especially annoyed by aircraft. It reduced one source of bias without making participation random.
Noise was measured with a Brüel & Kjær 2236 sound-level meter at 26 stations in the exposed area and three in the control area. Measurements were made between 7 am and 6 pm during October 2003–November 2004, with 20-minute samples each hour. Background estimates excluded aircraft and unusual events, permitting assessment of aircraft intrusion relative to background noise. The noise gap index concerns this contrast: identical aircraft noise can be more intrusive against a quieter background.
Using an instrument and specified sampling procedure supports consistent measurement beyond residents' opinions. Nevertheless, daytime sampling does not fully represent night-time exposure or sleep disruption. Researcher safety affected measurement choices. A measured sound level at a station is also an imperfect estimate of every resident's actual exposure inside their home.
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