Sarah,
I'm not familiar with the stats originally used.
However, very little research has looked at decent lengths of breastfeeding and risk of breast cancer- and it seems that this is an area where short durations of breastfeeding make little difference. The exception is one study from China- I tend to use this one when talking about long term breastfeeding. Abstract below.
Karleen Gribble
Australia
Zheng, T., L. Duan, et al. (2000). "Lactation reduces breast cancer risk in Shandong Province, China." American Journal of Epidemiology. 152(12): 1129-1135.
Results from studies of western populations investigating lactation and breast cancer risk have been inconsistent. To examine this issue, the authors conducted a hospital-based case-control study in Shandong Province, China, in 1997-1999. A total of 404 cases and an equal number of controls were included. Detailed information regarding lactation, menstruation, and reproduction was collected through in-person interview. The authors found a significant inverse association between duration of lactation and breast cancer risk. For women who breastfed for more than 24 months per child, the odds ratio was 0.46 (95% confidence interval (CI): 0.27, 0.78) when compared with those who breastfed for 1-6 months per child. A significantly reduced risk of breast cancer was also found for those whose lifetime duration of lactation totaled 73-108 months (odds ratio = 0.47, 95% CI: 0.23, 0.95) and for those who breastfed for > or =109 months (odds ratio = 0.24, 95% CI: 0.11, 0.53). The test for trend was statistically significant for both mean duration of lactation per child (p = 0.02) and lifetime duration of lactation (p = 0.00). Further stratification by menopausal status resulted in the same conclusion. These data suggest that prolonged lactation reduces breast cancer risk.
On 16/05/2012, at 7:05 AM, Sarah Vaughan wrote:
> On 15/05/2012 21:22, Sara wrote:
>> Norma, I enjoyed seeing your daughter's calming words and demonstrations. But I gotta ask about the news commentator's statistics: 'every year you bf your baby your risk of breast ca goes down by 32%"? From what baseline? The previous year's risk? So there's diminishing gain with increasing years nursed? It can't be a static benchmark because, um, after 3 years you what, give breast ca to the baby?<not very funny joke> - What I'm asking is, how does this work? What are the statistics?
> Uh, I'd question his figures, for starters. As I understand it, the Lancet meta-analysis at http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2802%2909454-0/fulltext is considered to be the most definitive study on the subject in terms of research quality, and they found a reduction of risk of 4.3% per year of breastfeeding. But, yes, whatever percentage reduction it is is from the baseline of where that year started, if you follow. (So, if we take 4.3% as the reduction per year, then one year of breastfeeding would reduce your risk by 4.3%, the second year would reduce your risk by 4.3% of the remaining 95.7% which is 4.1%, the third year would reduce your risk by 4.3% of the remaining 91.6% which is 3.94%... etc.)
>
>
> Best wishes,
>
> Dr Sarah Vaughan (hoping that made some kind of coherent sense!)
> MBChB MRCGP
>
> ***********************************************
>
> Archives: http://community.lsoft.com/archives/LACTNET.html
> To reach list owners: [log in to unmask]
> Mail all list management commands to: [log in to unmask]
> COMMANDS:
> 1. To temporarily stop your subscription write in the body of an email: set lactnet nomail
> 2. To start it again: set lactnet mail
> 3. To unsubscribe: unsubscribe lactnet
> 4. To get a comprehensive list of rules and directions: get lactnet welcome
***********************************************
Archives: http://community.lsoft.com/archives/LACTNET.html
To reach list owners: [log in to unmask]
Mail all list management commands to: [log in to unmask]
COMMANDS:
1. To temporarily stop your subscription write in the body of an email: set lactnet nomail
2. To start it again: set lactnet mail
3. To unsubscribe: unsubscribe lactnet
4. To get a comprehensive list of rules and directions: get lactnet welcome
|
