Breast cancer detection rates, and standardised detection ratios for prevalence screening in the New Zealand breast cancer screening programme.

OBJECTIVES: To calculate breast cancer detection to expected incidence ratios and standardised detection ratios (SDRs) for the New Zealand breast cancer screening programme. METHOD: Breast cancer registrations for 1976-1999 were obtained from the New Zealand Cancer Registry. Using these registrations, the incidence in the absence of screening was projected for 1999 and 2000. These projections, and the invasive breast cancers detected in the New Zealand programme during 1999 and 2000, were used to calculate the detection to expected incidence ratios and SDRs. RESULTS: In 1999, the breast cancer detection rate was 5.6 per 1000 women screened. The expected incidence among these women in the absence of screening was 2.3 per 1000, a detection to expected incidence ratio of 2.4. The SDR was 0.84 (0.76-0.94). In 2000, the breast cancer detection rate was 6.0 per 1000 women screened. The expected incidence among these women in the absence of screening was 2.4 per 1000, a detection to expected incidence ratio of 2.5. The SDR was 0.90 (0.81 - 0.99). CONCLUSIONS: In the first two years of the national programme, detection to expected incidence ratios were less than 3.0, and the SDR results were below 1.0. It may be unrealistic to expect new screening programmes to achieve SDRs of 1.0 immediately. At a similar stage, the UK National Health Service Breast Cancer Screening Programme (NHSBSP) also reported SDRs of less than 1.0 and therefore lower than expected cancer detection rates compared with the Swedish Two-County trial. An encouraging finding was that SDRs in five of the six screening regions improved in the second year of the New Zealand screening programme.

Clinical outcomes of the Otago-Southland Breast Cancer Screening Programme 1991-1996.

AIM: To document the clinical outcome of the Otago-Southland Breast Cancer Screening Programme through its first two rounds of screening, from 1991-1996. METHODS: Review and analysis of clinical and pathological records. RESULTS: In the first round of screening, 13,876 women were screened, giving 75% uptake; 12.2% were referred for assessment and 126 cancers detected, 9.1 per thousand women screened. For the 9946 incidence screens in the second round, 3.9% of women screened were referred to assessment and 50 cancers detected, 5.0 per thousand women screened. The uptake and cancer detection rates exceed the targets and exceed other published results; the size distribution of the cancers detected was comparable to the Swedish two-counties study, showing that the results should produce an ultimate mortality reduction. The referral rate to assessment was higher than expected in the first round of screening, but within the targeted range in the second round. The benign to malignant ratio for all biopsies was 1.4:1 for the prevalence screen of the first round and 1.2:1 for the incidence screens in the second round, both exceeding the targets set. CONCLUSIONS: The results show that the uptake and clinical results of the programme exceed expectations and that a large number of small invasive tumours have been successfully detected. These results are comparable to the best of overseas studies, and give confidence that mortality reductions will ultimately occur.

Ethnic differences in parent/infant co-sleeping practices in New Zealand.

AIM: This study was designed to monitor changes in the prevalence of risk factors for sudden infant death syndrome (SIDS) in the New Zealand population. The behaviour of interest is parent/infant co-sleeping. This paper reports parent/infant co-sleeping arrangements of different ethnic groups in New Zealand. METHODS: A stratified random sample of 6268 infants attending Plunket clinics for their three and six-month visits was taken over the years 1995-1996. Maori and Pacific infants were oversampled. Parents who shared a bed with their infant were asked how they arranged the babies sleeping place according to pre-coded diagrams. Routine parent/infant co-sleeping was defined as "bed sharing at least four nights over the last two weeks". RESULTS: There were 2693 infants who shared the bed with their sleeping parents during at least one of the previous 14 nights. Of these infants, 1060 routinely shared the parents' bed. At three months, 56% of routinely co-sleeping infants slept directly in the bed, 29% slept in a raised position, 3% slept in a carrycot or basket, and 5% in other positions. At six months, 60% of the routinely co-sleeping infants slept directly in the bed with their parents, 23% slept in a raised position, 1% slept in a carrycot or basket, and 7% in other positions. There were significant differences in the co-sleeping locations by ethnicity. CONCLUSION: There is still some ongoing dispute as to whether parent/infant co-sleeping is a risk factor for SIDS. This study has identified differences in the way infants co-sleep with their parents and this can be used to clarify infant care practices in relation to SIDS.

Breastfeeding rates in New Zealand in the first 6 months and the reasons for stopping.

AIM: To assess the prevalence of breastfeeding in the first 6 months post partum, and to elicit the reasons for stopping breastfeeding. METHODS: A longitudinal cohort study of 4286 New Zealand infants born between 2 July 1990 and 30 June 1991. Mothers were asked at 6 weeks, 3 months and 6 months whether they were breastfeeding or had ever breastfed their babies. If they had breastfed their babies but had now stopped breastfeeding, they were asked how old the baby was when they stopped and the reasons for stopping. RESULTS: Feeding data was available on 3929 of the 4286 infants enrolled in the study. At birth 93.8% (n = 3685) infants were exclusively breastfed. No infants were partially breastfed. At 6 weeks, 3 months and 6 months post partum, the breastfeeding rates were 79.5% (68.4% exclusive), 71.3% (47.6% exclusive), and 56% (2.5% exclusive), respectively. The most common reason for stopping breastfeeding was perceived inadequate supply of breast milk (29%, 29% and 33% of mothers who stopped between birth to 6 weeks, 6 weeks to 3 months and 3 months to 6 months, respectively), apart from Pacific Island mothers, whose main reason for stopping breastfeeding between six weeks and three months post partum was returning to work or study (38% of mothers who stopped). CONCLUSIONS: The decline in breastfeeding rates with length of time post partum could be reduced with education of breastfeeding mothers and health professionals about the management of breastfeeding problems and early infant behaviour and growth. Support by employers or education facilities for breastfeeding mothers who are working or studying may help to maintain breastfeeding rates.

Immunisation status and demographic characteristics of New Zealand infants at 1 year and 2 years of age.

AIMS: To ascertain the immunisation status of a cohort of infants at 1 year and 2 years of age. METHODS: The Plunket National Child Health Study is a longitudinal study of 4286 New Zealand children, based on an ethnically stratified and geographically representative sample of children born between 2 July 1990 and 30 June 1991. The immunisation status of these children was examined at 1 year and 2 years of age. RESULTS: By 1 year and 2 years of age, 92.5% and 83.3%, respectively, had received all their age appropriate immunisations. Children who were incompletely immunised at 2 years of age were more likely to have mothers who were of high parity, or had higher or lower levels of education, or who had a later initial attendance at the doctor for this pregnancy, or who did not attend antenatal classes. The most common reason why immunisations had been delayed was because of ill health (of the children) at the time of the immunisation. Only 1.4% had had no immunisations at all by 2 years of age. CONCLUSIONS: This study challenges the widely held views that New Zealand has a poor child health immunisation record, and that antiimmunisation beliefs are widespread. New Zealand needs systems in place which give current immunisation rates rather than relying on point prevalence or retrospective studies. Information about contraindications to immunisation needs to be reinforced with immunisation providers and advisors, and parents.

Alcohol consumption by New Zealand women during pregnancy.

AIMS: Despite the known negative effects of alcohol consumption during pregnancy, there is little basic epidemiological information on this group of women. The present study aims to provide such information. METHODS: The Plunket National Child Health Study is a longitudinal study of 4286 New Zealand children, based on an ethnically stratified and geographically representative random sample of children born between 2 July 1990 and 30 June 1991. The drinking habits of the mothers of these children are examined. RESULTS: During pregnancy 41.6% of women consumed alcohol. Compared with abstainers, they tended to be older, have higher educational qualifications, lower parity, higher socioeconomic status and be European or Maori. Of those women who consumed alcohol, the frequency of consumption was rare (between one and three times in pregnancy) in 13.6% of cases, occasional (more than three times in pregnancy but less than weekly) in 67.7% of cases, and frequent (more than once a week) in 18.7% of cases. Those who frequently consumed were more likely to have higher socioeconomic status. For pregnant women in New Zealand, the sociodemography of those having high rates of alcohol consumption does not coincide with the sociodemography of those who have high rates of smoking. CONCLUSIONS: Programmes aimed at reducing alcohol consumption during pregnancy should take account of the at-risk groups of women as identified above. In particular they should include women of higher socioeconomic status in their target groups.