more on night shifts, noctural night at home and breast cancer

[Lani]

ABSTRACT: Shift Work, Light at Night, and Breast Cancer on Long Island, New York [American Journal of Epidemiology; Subscribe; Sample]
The hypothesized association between breast cancer and circadian disruption was evaluated in the Electromagnetic Fields and Breast Cancer on Long Island Study. Participants included 576 women with breast cancer diagnosed from August 1996 to June 1997 and 585 population-based controls (87% and 83% participation rates, respectively) aged <75 years and living in the same Long Island, New York, home for ?15 years. An in-person interview ascertained light-at-night exposure histories through shift work (previous 15 years) and at home (previous 5 years). Odds ratios and 95% confidence intervals were estimated by unconditional multivariate logistic regression. Breast cancer was not associated with overall shift work (odds ratio (OR) = 1.04, 95% confidence interval (CI): 0.79, 1.38) or evening shift work (OR = 1.08, 95% CI: 0.81, 1.44). However, overnight shift workers were at lower risk than women never working shifts (OR = 0.55, 95% CI: 0.32, 0.94). Women who frequently turned on lights at home during sleep hours (?twice/week and ?twice/night) had increased risks (OR = 1.65, 95% CI: 1.02, 2.69). The latter results suggest positive associations with residential light-at-night exposure, or they could reflect response biases. Furthermore, overall and evening shift work were not significant factors, and analyses of overnight shift workers yielded reduced risk estimates. The study thus provides mixed evidence for the light-at-night hypothesis.

[Montana]

"Women who frequently turned on lights at home during sleep hours (?twice/week and ?twice/night)"

Well, who has kids who didn't get up with them during the night? I have 4....I was up many times during the night over the years.

[al from Canada]

Lani, doesn't melatonin reset the biological clock / circadian rhythm? there has been a lot of recent interest in melatonin and breast cancer.

Al

[Lani]

I haven't reviewed the melatonin literature for about five months--I did so extensively prior to that. It is truly an area where the amount understood is miniscule. In fact, we still do not understand even WHY we sleep! (which seems to be one of the basic questions of physiology and/or brain function!)

Whether to take melatonin, how much and when is really just playing the lottery at present. It seems one of melatonin's effects is as an aromatase inhibitor--and one can get THAT effect in other ways. I am certain there are many more effects.


This study was done retrospectively and relied on the subjects memories and subjective judgements (was there more light/incomplete darkness/etc and how often). Certainly not as accurate as one would like in drawing conclusions.

RB--Perhaps the midnight sun in Scandinavia counteracts their high fish oil intake as Scandinavians do NOT have a low rate of breast cancer.

[R.B.]

I am not familiar with the scandinavian stats.

From populations study reports seen or seen reported Icelanders from recollection do /did have lower rates as do/did eskimo type populatons, Japanese, South African black fishing communities.

All the fish based trials I have seen are based on what did you eat.

I tend to ignore these unless they are correlated with blood and or tissue samples. A combination of talking to a student about the realities where participants are paid in dietary recording trials and the large number of factors that can impact on fat intake for me just do not provided enough certainty without corroberation based on testing for fats in lipids or better tissue.

I tend to take more comfort from trials albeit small in size that look at actual fats in the body in their determinations, and the argumants that some BCs have at least in part an inflamatory factor.

Melatonin could impact significnatly on inflamatory factors in the body for a number of reasons. Melatonin production can be altered by other factors. I think we are again in a situation where life style trials will not tell us definatively what we want to know unless we look at actual hormone (melatonin) levels in the women being considered.


RB.

[R.B.]

This is the sort of trial I beleive needs to be repeated on a much wider levels.

The results are very thought provoking.

RB



http://www.ncbi.nlm.nih.gov/entrez/q..._uids=11857389

1: Int J Cancer. 2002 Mar 1;98(1):78-83.Click here to read Links
N-3 and N-6 fatty acids in breast adipose tissue and relative risk of breast cancer in a case-control study in Tours, France.

* Maillard V,
* Bougnoux P,
* Ferrari P,
* Jourdan ML,
* Pinault M,
* Lavillonniere F,
* Body G,
* Le Floch O,
* Chajes V.

Laboratoire de Biologie des Tumeurs, Clinique d'Oncologie-Radiotherapie, Service de Gynecologie-Obstetrique, E.A. 2103, Unite de Recherche Associee Universite-INRA, CHU, Tours, France.

Experimental studies have indicated that n-3 fatty acids, including alpha-linolenic acid (18:3 n-3) and long-chain n-3 polyunsaturated fatty acids inhibit mammary tumor growth and metastasis. Earlier epidemiological studies have given inconclusive results about a potential protective effect of dietary n-3 polyunsaturated fatty acids on breast cancer risk, possibly because of methodological issues inherent to nutritional epidemiology. To evaluate the hypothesis that n-3 fatty acids protect against breast cancer, we examined the fatty acid composition in adipose tissue from 241 patients with invasive, nonmetastatic breast carcinoma and from 88 patients with benign breast disease, in a case-control study in Tours, central France. Fatty acid composition in breast adipose tissue was used as a qualitative biomarker of past dietary intake of fatty acids. Biopsies of adipose tissue were obtained at the time of surgery. Individual fatty acids were measured as a percentage of total fatty acids, using capillary gas chromatography. Unconditional logistic regression modeling was used to obtain odds ratio estimates while adjusting for age, height, menopausal status and body mass index. We found inverse associations between breast cancer-risk and n-3 fatty acid levels in breast adipose tissue. Women in the highest tertile of alpha-linolenic acid (18:3 n-3) had an odds ratio of 0.39 (95% confidence intervals [CI] = 0.19-0.78) compared to women in the lowest tertile (trend p = 0.01). In a similar way, women in the highest tertile of docosahexaenoic acid (22:6 n-3) had an odds ratio of 0.31 (95% CI = 0.13-0.75) compared to women in the lowest tertile (trend p = 0.016). Women in the highest tertile of the long-chain n-3/total n-6 ratio had an odds ratio of 0.33 (95% confidence interval = 0.17-0.66) compared to women in the lowest tertile (trend p = 0.0002). In conclusion, our data based on fatty acids levels in breast adipose tissue suggest a protective effect of n-3 fatty acids on breast cancer risk and support the hypothesis that the balance between n-3 and n-6 fatty acids plays a role in breast cancer. Copyright 2001 Wiley-Liss, Inc.

PMID: 11857389 [PubMed - indexed for MEDLINE]