Cross-cultural correlations of childhood growth and adult breast cancer

Childhood stature and adult cancer risk: the Boyd Orr cohort

Cancer risk in adulthood may be influenced by aspects of childhood diet. In the absence of direct dietary data, indirect measures of childhood diet and nutritional status, such as anthropometric measurements, may be useful in investigating diet-cancer associations. Previous studies suggest that taller adults may have increased cancer risk. Peak growth for different anthropometric measures occurs at different times and so differential associations with cancer risk may indicate periods of development that are particularly important in determining future risk. 2,642 traced members of the Boyd Orr cohort had measures of foot length, shoulder breadth, height, and leg length made when they were aged 2-14 years; trunk length was derived from the difference between overall height and leg length. Subjects were followed-up over 59 years to determine all-cause (n = 547) and site-specific (n = 97 for lung, 69 breast, 59 colorectal, 33 prostate, 320 not related to smoking) cancer deaths and registrations. There were no strong associations between childhood anthropometric measurements and adult cancer risk. Odds ratios (ORs) were broadly consistent with a slight increase in risk with increasing childhood stature but no single measure was of particular importance. The strongest associations were seen for breast cancer (OR per standard deviation increase in foot length: 1.16 (95% CI: 0.90, 1.51), shoulder breadth: 1.16 (0.91, 1.49) and trunk: 1.26 (1.00, 1.60), and prostate cancer (OR for foot length: 1.22 (0.86, 1.75)). There was little effect of adjustment for confounding factors and very limited evidence that associations differed with measures made prior to the onset of puberty (comparing the associations in children aged <8 vs. 8+ years). There was no evidence that any of the five indicators of childhood growth was more strongly related to cancer risk than the other measures.

Early Life Diet and the Risk for Adult Breast Cancer

A hypothesis postulating intrauterine and early life influences on the occurrence of breast cancer in adult life has received considerable support in the literature. We present alternative or complementary ways through which diet could affect breast cancer risk in this context. Emphasis is placed on evidence that reduced energy intake in early life is associated with smaller body size, which, in turn, constrains birth weight and subsequent development of offspring and is associated with reduced breast cancer risk.

Global trends in breast cancer incidence and mortality 1973-1997

BACKGROUND

Worldwide, breast cancer is the most common cancer and is the leading cause of cancer death among women.

METHODS

To describe global trends, we compared age-adjusted incidence and mortality rates over three decades (from 1973-77 to 1993-97) and across several continents.

RESULTS

Both breast cancer incidence and mortality rates varied 4-fold by geographic location between countries with the highest and lowest rates. Recent (1993-1997) incidence rates ranged from 27/100,000 in Asian countries to 97/100,000 among US white women. Overall, North American and northern European countries had the highest incidence rates of breast cancer; intermediate levels were reported in Western Europe, Oceania, Scandinavia, and Israel; and Eastern Europe, South and Latin America, and Asia had the lowest levels. Breast cancer incidence rose 30-40% from the 1970s to the 1990s in most countries, with the most marked increases among women aged > or =50 years. Mortality from breast cancer paralleled incidence: it was highest in the countries with the highest incidence rates (between 17/100,000 and 27/100,000), lowest in Latin America and Asia (7-14/100,000), and rose most rapidly in countries with the lowest rates.

CONCLUSIONS

Breast cancer incidence and mortality rates remain highest in developed countries compared with developing countries, as a result of differential use of screening mammograms and disparities in lifestyle and hereditary factors. Future studies assessing the combined contributions of both environmental and hereditary factors may provide explanations for worldwide differences in incidence and mortality rates.

Exposures in childhood, adolescence and early adulthood and breast cancer risk: a systematic review of the literature

A growing body of work indicates that exposures over the life course have important roles to play in the aetiology of breast cancer. This review synthesises the literature that has been published in the area of early life events and female breast cancer risk. The review finds some evidence, primarily from cohort studies on the relationship between birthweight and breast cancer, to suggest that in utero events are related to breast cancer risk in adulthood. Strong evidence to support a positive association between height and breast cancer exists. Postulated mechanisms for this relationship include the role of early diet in subsequent disease risk, and the influence of endogenous growth factors mediating the relationship. There is some evidence to suggest that leg length is the component of height which is generating the observed associations between height and breast cancer. There is no consistent pattern of association between relative weight in childhood or adolescence and risk of breast cancer. The evidence to suggest an association between physical activity in early life and breast cancer risk is convincing from case-control studies, but is not fully substantiated by the results of three cohort studies. There are inconsistent results regarding the association between smoking at a young age and breast cancer risk. There is little evidence for an association between passive smoking in early life and breast cancer risk. No clear association between early drinking and breast cancer risk exists. These results are discussed in relation to possible underlying mechanisms and health promotion strategies which could reduce breast cancer risk.

An investigation of soy intake and mammographic characteristics in Hawaii

This cross-sectional investigation in Hawaii explored the relation between soy foods and mammographic characteristics using two food frequency questionnaires and a computer-assisted density assessment method. Japanese and Chinese women reported significantly greater soy food intake than Caucasian women. Whereas soy intake and the size of the dense areas were not related, soy intake and percent mammographic densities were positively associated. The size of the entire breast and the nondense area (ie the fatty part of the breast) were inversely related to soy intake. These results suggest the hypothesis that soy foods by themselves or as part of an Asian dietary pattern may affect the growth of the female breast before adulthood, but the possible mechanisms of action have to be explored in future studies.

Breast cancer and electric power

Breast cancer is a leading cause of death among women in industrialized societies. It is far less common in less industrialized nations and the reason for this difference is unclear. One possibility is the distribution and use of electricity which results in two new exposures in the human environment: light-at-night and electromagnetic fields. These can reduce nocturnal melatonin production. Melatonin, in turn, has a protective effect on breast cancer in experimental animals.

International differences in body height and weight and their relationship to cancer incidence

The relationship between body size (adult height and weight) and cancer incidence was investigated in an international ecological study of 24 populations. Site-specific and total cancer incidence rates (age standardized) from 1973 to 1977 were correlated with body size data generally obtained between 1954 and 1974. All-sites cancer incidence was highly correlated with height among both men (r = 0.50; p less than or equal to 0.01) and women (r = 0.70; p less than or equal to 0.001). Among men, there were significant correlations between height and cancers of the central nervous system (r = 0.72), prostate (r = 0.66), bladder (r = 0.65), pancreas (r = 0.59), lung (r = 0.47), and colon (r = 0.46). Significant correlations were observed for cancers of the rectum (r = 0.76), pancreas (r = 0.75), ovary (r = 0.73), central nervous system (r = 0.68), breast (r = 0.65), uterine corpus (r = 0.50), and bladder (r = 0.48) in women. Adjustment for weight altered these correlations only minimally. Weight was significantly correlated to all-sites cancer only among women (r = 0.44; p less than 0.05), and site-specific correlations were significant for the same sites as for height, but the magnitude of the correlation coefficients was somewhat diminished. In addition, adjustment for height greatly reduced the correlations with weight. These findings support previously observed associations between height and specific cancers (e.g., breast and colon) and identify several additional cancer sites that may be similarly related.

Energy balance, body size, and cancer

Increased energy intake and physical inactivity have been shown to heighten the risk of breast, large bowel, and other cancers. Large body size and fatness, as measured by adult stature, body weight and body mass indices, are positively related to a variety of cancers, including breast, colorectum, prostate, endometrium, kidney, and ovary, as well as to total cancer incidence or mortality in many investigations, although conflicting reports exist. Adult weight gain has also been specifically implicated in a few etiologic studies of breast and large bowel cancer. Furthermore, increased birthweight and childhood stature have been linked to increased risk of leukemia, lymphoma, osteogenic sarcoma, and central nervous system malignancies between infancy and young adulthood. Greater body weight also adversely affects breast cancer survival. These findings are complementary and support a role for positive energy balance in promoting human carcinogenesis. Potential mechanisms are discussed.

Bowel function and breast cancer in US women

We studied bowel function in relation to 123 breast cancer cases among 7,702 women from the US NHANES I Epidemiologic Follow-up Study. Results suggest a slight increased risk of breast cancer for both decreased frequency of bowel movements (relative risk = 1.5, 95% confidence interval = 0.8, 2.7) and firm stool consistency (RR = 1.8, 95% CI = 1.0, 3.2.) These observations are consistent with an hypothesized association between constipation and increased risk of breast cancer.

X-ray examinations during pregnancy: National Natality Surveys, 1963 and 1980

Based on 1963 and 1980 National Natality Surveys, the rate of medical x-ray examinations during pregnancy per 100 mothers fell 34.2 percent. A decrease in chest x-ray examinations accounted for almost all of the decline in total x-ray examinations. The reductions were greater for older mothers and those who were not White. While the number of births fell from 4,071,000 in 1963 to 3,612,000 in 1980, the number of pelvimetry examinations actually increased by 45,000.