Methods
The New South Wales Population Health Survey uses random digit dialling to contact households with private telephones. One person from the household is randomly selected for inclusion in the survey. For analysis, the sample is weighted to adjust for differences in the probabilities of selection among subjects, stratified for differences between the age and sex structure of the sample and the Australian Bureau of Statistics mid-year population estimates for each area health service (excluding residents of institutions). This enables calculation of prevalence estimates for the state population rather than the respondents selected. Further information on the survey's probabilistic sampling, weighting procedures, and calculation of prevalence estimates, can be found elsewhere.[1,2]
Data are analysed using SAS version 9.[3] The SURVEYFREQ procedure is used to calculate prevalence estimates and 95% CI for the estimates. For pairwise comparison of subgroup estimates, the p-value for a two-tailed test is calculated using the normal distribution probability function PROBNORM.
Socioeconomic status is derived from the Index of Relative Socio-Economic Disadvantage,[4] which is based on a number of underlying variables such as family characteristics, household income, personal educational qualifications, employment status, and occupation profile. The index is grouped into 5 quintiles, with quintile 1 being the least disadvantaged and quintile 5 being the most disadvantaged. This index is assigned by postcode of residence.
Geographic remoteness is derived from the Accessibility-Remoteness Index of Australia Plus (ARIA+).[5] This index is derived from the road distances from populated localities to the nearest service centres across Australia. For each locality, the accessibility to services is expressed as a continuous measure from 0 (high accessibility) to 15 (high remoteness) and is grouped into 5 categories: major cities, inner regional, outer regional, remote, and very remote. These 5 categories are assigned by postcode of residence. Because of small numbers in the remote and very remote categories, these categories have been combined in the analysis.
Studies demonstrate that a person's appraisal of his or her general health is a strong and independent predictor of future morbidity and mortality, even after controlling for physical and psychosocial and socioeconomic factors.[6] In the survey respondents aged 16 years and over are asked: Overall, how would you rate your health during the last 4 weeks: was it excellent, very good, good, fair, poor, or very poor? Responses of excellent, very good, and good are combined into a positive rating.
Alcohol consumption is measured against the Australian Alcohol Guidelines.[7] Risk drinking includes those who consumed alcohol every day, consumed more than 4 if male or 2 if female standard drinks per day, or consumed more than 6 if male or 4 if female standard drinks on any occasion in the last 4 weeks. High risk drinking includes those who consumed more than 11 if male or 7 if female standard drinks on any occasion in the last 4 weeks.
For breast cancer screening, the indicator excludes those who had an existing cancer or breast problem. For cervical cancer screening, the indicator excludes those who had a hysterectomy. For bowel cancer screening, the indicator excludes those who had been screened as part of follow-up treatment.
Adequate fruit and vegetable consumption is measured against the National 'Go for 2 & 5' Fruits and Vegetables Campaign, which recommends 2 serves of fruit and 5 serves of vegetables each day. This campaign is informed by the Dietary Guidelines for Australian Adults, and the Australian Guide to Healthy Eating.[8,9,10]
Adequate physical activity is derived from the National Physical Activity Guidelines for Adults, which recommend at least 30 minutes of moderate activity on most, and preferably all, days of the week, using questions asked in the Active Australia Survey. Adequate physical activity is defined as undertaking physical activity for a total of 150 minutes per week over 5 separate occasions.[11,12]
Psychological distress is derived from the K10 short screening scale, a 10-item questionnaire that measures non-specific psychological distress based on questions about the level of nervousness, agitation, psychological fatigue and depression in the most recent 4-week period. Responses to the questionnaire are classified into 4 categories: low psychological distress, when the K10 score is 10-15; moderate psychological distress, when the K10 score is 16-21; high psychological distress, when the K10 score is 22-29; and very high psychological distress, when the K10 score is 30 or higher. At both the population level and individual level the K10 measure is a barometer for psychological distress without identifying its cause.[13]
Overweight and obesity is derived from self-reported height and weight. Body Mass Index (BMI) is calculated by dividing a person's weight (in kilograms) by their height (in metres squared). The resulting BMI is classified into 4 categories: underweight when the BMI is less than 18.5, acceptable or ideal weight when the BMI is greater than or equal to 18.5 and less than 25, overweight when the BMI is greater than or equal to 25 and less than 30, and obese when the BMI is greater than or equal to 30. Although studies have shown self-reported BMI results in an under-estimation of measured BMI, it is still useful for ongoing surveillance of population health.
The table below shows that the 2006 weighted survey sample compares well with the state population, according to the 2006 Census of Population and Housing, for sex, age, indigenous status, and employment status.[14]
| Weighted Sample 2006 Survey (n=5,480) % | New South Wales Population 2006 Census (N=2,529,649) % | |
| Sex | ||
| Males | 48.6 | 47.8 |
| Females | 51.4 | 52.2 |
| Age groups | ||
| 45-54 | 36.6 | 35.7 |
| 55-64 | 29.0 | 28.4 |
| 65-74 | 18.5 | 18.4 |
| 75+ | 15.9 | 17.4 |
| Indigenous status | ||
| Aboriginal and Torres Strait Islander origin | 1.1 | 1.0 |
| Highest level of school completed | ||
| Never attended school | 1.0 | 1.9 |
| Year 8 or below | 11.3 | 13.3 |
| Year 9 or equivalent | 6.8 | 11.9 |
| Year 10 or equivalent (Intermediate) | 35.6 | 32.4 |
| Year 11 or equivalent | 2.3 | 4.6 |
| Year 12 or equivalent (Matriculation/Leaving) | 43.0 | 35.8 |
| Born in Australia | ||
| Australia | 72.1 | 60.7 |
| Formal marital status | ||
| Married | 71.2 | 63.5 |
| Widowed | 10.3 | 12.5 |
| Separated but not divorced | 2.3 | 3.8 |
| Divorced | 9.6 | 11.9 |
| Never married | 6.6 | 8.4 |
| Employment status | ||
| Employed Full-time (>=35hours a week) | 27.2 | 28.5 |
| Employed Part-time (<35 hours a week) | 13.9 | 12.6 |
| Employed (on leave/hours not stated) | 3.5 | 2.7 |
| Unemployed | 1.9 | 1.9 |
| Not in the labour force | 53.3 | 54.2 |
References
- Centre for Epidemiology and Research. NSW Population Health Survey: Description of Methods. Sydney: NSW Department of Health, 2008. Available online at www.health.nsw.gov.au/publichealth/surveys/otherpub.asp (accessed 11 June 2008).
- Centre for Epidemiology and Research. NSW Population Health Survey: Review of Weighting Procedures. Sydney: NSW Department of Health, 2004. Available online at www.health.nsw.gov.au/publichealth/surveys/otherpub.asp (accessed 11 June 2008).
- SAS Institute. The SAS System for Windows version 9. Cary, NC: SAS Institute Inc., 2002.
- Australian Bureau of Statistics. Information Paper: An Introduction to Socio-Economic Indexes for Areas (Preliminary). Catalogue no. 2039.0. Canberra: ABS, February 2008.
- Australian Bureau of Statistics. ASGC Remoteness Classification: Purpose and Use. Census Paper no. 03/01. Canberra: ABS, 2003.
- Eriksson I, Unden A-L, and Elofsson S. Self-rated health. Comparisons between three different measures. Results from a population study. Int J Epidemiol 2001; 30: 326-333.
- Australian Government Department of Health and Aged Care. Australian Alcohol Guidelines. Canberra: Australian Government Department of Health and Aged Care, 2006. Available online at www.alcohol.gov.au (accessed 11 June 2008).
- National 'Go for 2 and 5' Fruits and Vegetables Campaign website at www.healthyactive.gov.au (accessed 11 June 2008).
- National Health and Medical Research Council. Dietary Guidelines for Australian Adults. Canberra: NHMRC, 2003. Available online at www.nhmrc.gov.au (accessed 11 June 2008).
- National Health and Medical Research Council. Australian Guide to Healthy Eating. Canberra: NHMRC, 2003. Available online at www.health.gov.au (accessed 11 June 2008).
- Australian Government Department of Health and Aged Care. National Physical Activity Guidelines for Australians. Canberra: Australian Government Department of Health and Aged Care, 2005. Available online at www.health.gov.au (accessed 11 June 2008).
- Australian Institute of Health and Welfare. The Active Australia Survey: A guide and manual for implementation, analysis and reporting. Canberra: AIHW, 2003. Available online at www.aihw.gov.au (accessed 11 June 2008).
- Kessler RC, Andrews G, Colpe LJ, Hiripi E, Mroczek DK, Normand S-LT, Walters EE, Zaslavsky A. Short screening scales to monitor population prevalences and trends in nonspecific psychological distress. Psychological Medicine 2002, 32(6): 959-976.
- Australian Bureau of Statistics. 2006 Census of Population and Housing. Catalogue no. 2914.0. Canberra: ABS, 2006. Available online at www.censusdata.abs.gov.au.
| Source: | New South Wales Population Health Survey 2007 (HOIST). Centre for Epidemiology and Research, NSW Department of Health. |
| Print version: | Although this page can be printed directly from your web browser, a higher quality version is available as a PDF file that can be printed or viewed on screen. |
| Produced by: | Centre for Epidemiology and Research, Population Health Division, NSW Department of Health. |
| Last updated on: | 1 June 2008 |