Notes Washed Up in a Bottle

Don. W. MacCorquodale M.D. M.S.P.H.

Periodic Notes From the Field on Philosophy and Science.

INFANT BIRTH WEIGHT AND PARENTAL MORTALITY

Fetal undernutrition is said to be a risk factor for future disease with risk particularly increased if there is overnutrition and rapid growth during the postnatal period.  It has been suggested that common genetic factors could be related to both restricted fetal growth and later insulin resistance and cardiovascular disease.  The authors conducted a cohort study and a meta-analysis to examine cardiovascular disease risk in parents in relation to certain birth characteristics of their infants (Smith, George Davey et al.  Offspring birth weight and parental mortality:  Prospective observations and meta-analysis.  Am J Epidemiology 2007:  166:  160-169). 

All births in England and Scotland during one week in March 1958 were included in the Perinatal Mortality Study.  When the surviving children were 7 years old, they were contacted, and the study was continued as the National Child Development Study.

Data for the infant cohort members, including birth weight and gestational age, were collected by midwives who attended the deliveries.  BMI of the parents was recorded, and social class was based on the father’s occupation according to the Registrar General’s classification (I-II; III nonmanual; III manual, and IV-V).  Data was also collected on maternal smoking reported in 1958 (none; up to the fifth month of pregnancy; and after the fifth month of pregnancy).

The main end points used in the study were all-cause mortality, mortality from circulatory disease, coronary heart disease, and stroke.  The authors also examined the association of birth weight with mortality from:
          Respiratory disease       Chronic obstructive lung disease
          Cancer                           Cancer of the stomach, lung, prostate, and breast, and
          Suicide, accidents, and violence 

The authors main hypotheses “concerned the association of offspring birth weight with parental cardiovascular disease.”  Other outcomes were assessed as a test of specificity to determine whether associations with cardiovascular disease might be explained by residual confounding.  “For example, associations between offspring birth weight and accidents and violence and smoking- or alcohol-related mortality, in addition to an association with cardiovascular disease, would indicate residual confounding by socioeconomic position and smoking as an explanation for the association.”

Mothers who had larger babies were older, had higher BMI, were taller, were less likely to smoke during pregnancy, and were less likely to suffer from preeclampsia.  For fathers, results were in the same direction, although weaker for BMI, height, and smoking. 

Offspring weight was inversely associated with maternal mortality from coronary heart disease, stroke, chronic obstructive pulmonary disease, and lung cancer.   Stomach cancer and suicide also showed strong inverse associations for mothers, but with considerable imprecision of the estimates.  For fathers, the associations were weaker, although in the same directions as for mothers, with the exception of accidental and violent deaths, which showed a stronger association in fathers than in mothers. 

The authors adjusted for age, gender of the offspring and additionally for offspring gestational age, social class of the father, parity of the mother, and eclampsia during pregnancy.  The mother’s mortality was adjusted for her height, BMI in 1958, and smoking during pregnancy.  The adjustments attenuated, but did not abolish, the associations of offspring birth weight with maternal mortality from coronary heart disease and stroke.  There was considerably greater attenuation of the associations of offspring birth weight and mortality from chronic obstructive pulmonary disease and lung cancer after adjustment.  A similar picture was seen for fathers, although there was no evidence of an inverse association with stroke after age adjustment. 

When the authors restricted the meta-analysis to three studies that had assessed associations in both mothers and fathers, the pooled effect regarding cardiovascular disease mortality remained stronger in mothers than in fathers. 

The authors summarized their findings by stating, “we found an inverse association between offspring birth weight and cardiovascular disease mortality in mothers and fathers that persisted after adjustment for potential confounding factors and was somewhat weaker for fathers compared to mothers.”  They suggested that the association “may reflect maternal/fetal nutritional factors and intrauterine programming, as women who themselves had poor fetal growth and low birth weight tend to have offspring who are smaller for their gestational age.”  They added that a possible genetic mechanism could explain the associations in both parents. 

COMMENT:  No surprises here.  Some maternal characteristics that are associated with having a low birth weight infant are also associated with increased risk of cardiovascular disease.  I would have been rather surprised if the results of this study had been of such a nature as to support the hypothesis that genetic factors were associated with increased risk of bearing low birth weight infants and being at increased risk of cardiovascular disease. 

CANCER IN ASIAN AMERICANS

Although Asian Americans and Pacific Islanders have lower incidence and mortality rates from all cancers combined than all other racial /ethnic groups they are the only major US racial/ethnic group for which the annual number of deaths from cancer exceeds that for heart disease.  Asian Americans are at lower risk for cancer of the lung, colon and rectum, breast and prostate, they have higher rates of cancers related to infectious conditions, particularly tumors of the cervix, stomach, liver and nasopharynx (McCracken, Melissa et al.  Cancer incidence, mortality and associated risk factors among Asian Americans of Chinese, Filipino, Vietnamese, Korean, and Japanese ethnicities.  CA – A Journal for Clinicians 2007; 57:  190-205). 

No national cancer incidence, mortality or risk factor data are available for Asian American ethnic groups.  Data are available for this population from some of the Surveillance, Epidemiology, and End Results (SEER) regions, including the states of California and Hawaii.  Information on cancer incidence and mortality for ethnic groups of Asian Americans and non-Hispanic Whites in California for the years 2000 to 2002 were provided by the Los Angeles Cancer Surveillance Program and the California Cancer Registry. 

The authors analyzed data for all cancers combined, the four most common cancers, i. e., lung, colorectal, breast, and prostate, and three other cancer sites, namely, stomach, liver, and cervix, for which risk is known to be high in Asian Americans.  Information on the prevalence of selected behavioral risk factors for cancer such as smoking, overweight, physical inactivity, and alcohol intake as well as use of various cancer screening tests was available from the California Health Interview Survey, a telephone survey in 2003 that over sampled minority populations in the state. 

Chinese Americans are the largest Asian ethnic group in the United States.  The Chinese American population is concentrated in California, 40.3%, New York, 17.5%, and Texas, 4.4%.  Filipinos are the second largest Asian group in the United States concentrated in California, 49.6%, and Hawaii, 9.2%.  About half of all Asians live in the West, mostly concentrated in California.  In 2000, Asian Americans represented 4.2% of the total U. S. population. 

Japanese Americans are the most acculturated, have the highest socioeconomic status, and the smallest average household size.  Education levels are much higher for persons of Indian, Chinese, Filipino, and Japanese descent than among Cambodians, Hmong, and Laotians.  Fully 44.1% of the overall Asian population achieved a bachelor’s degree, but fewer than 10% of the Cambodians, Hmong, and Laotians graduated from college, and only half were high school graduates. 

Chinese

Chinese males had the third highest incidence and mortality rates for colorectal cancer among the Asian ethnic groups.  The colorectal cancer incidence and mortality rates for Chinese females were the second highest.  The high rate of colorectal cancer among Chinese in California contrasts sharply with the low ranks in China, and the increase in risk with time since migration implicates behaviors associated with the Western lifestyle. 

Chinese women have the second highest lung cancer incidence rate and the highest lung cancer mortality rate of all the Asian ethnic groups on California.  Their high rates of lung cancer are unexpected, given the low prevalence of smoking among Chinese women in California.  Only 2.2% of Chinese women reported that they were current smokers and only 5.4% that they were exsmokers during the California Health Interview Survey.  Chinese American women are commonly exposed to secondhand smoke at home and at the worksite.  Exposure to cooking oil from high temperature frying may contribute to lung cancer risk among Chinese women in the United States, as it has been proposed to do in China. 

Filipino

Filipino men had the highest incidence and mortality rates for prostate cancer among all Asian ethnic groups.  International studies suggest that a diet high in saturated fat may be a risk factor and that the risk of dying of prostate cancer may be associated with obesity. 

Filipino men have the second highest incidence and the highest mortality rate from lung cancer among the Asian ethnic groups, although the prevalence of current smoking is higher in Korean and Vietnamese men.  These differences may reflect differences in age at initiation of smoking as well as intensity and duration of smoking in the populations. 

Filipino women had the second highest incidence and the highest mortality rate for breast cancer.  Overweight and obesity are established risk factors for postmenopausal breast cancer.  The percent of Filipino women who are overweight (35.5%) was higher than that of any other Asian ethnic group.  Acculturation and adoption of Westernized diets and behaviors may contribute to the high breast cancer burden among Filipino women. 

Cervical cancer is the second most common malignancy after breast cancer for women worldwide and is more common in Asian American women than in non-Hispanic White women in the U. S.  The incidence of cervical cancer among Filipino women is higher than that in Whites, although not as high as among Korean and Vietnamese women. 

Filipino Americans have among the highest levels of income, education, and health insurance of all Asian ethnic groups. 

Vietnamese

Vietnamese have by far the highest incidence and death rates from liver cancer of all the Asian ethnic groups.  Their incidence is over 7 times higher than the incidence among non-Hispanic White men.  Among Vietnamese women, the incidence and death rates from liver cancer are lower than in men, but second only to Korean women.  Chronic infection with hepatitis B virus causes most cases of liver cancer, and it is common in regions where liver cancer is endemic.

Vietnamese women in California had the highest incidence and mortality from cervical cancer compared with other Asian ethnic groups.  Human papilloma virus (HPV) is a universal risk for cancer of the cervix, although variations in HPV infection rates and types do not appear to explain the large international variation in cervical cancer risk.  High cervical cancer incidence and mortality in developing countries is likely related to lack of access to Pap testing. 

Vietnamese males had the second highest incidence and the third highest death rate from stomach cancer.  Vietnamese women have lower rates than men, but still have high risk of developing and dying from stomach cancer.  It is not clear why Vietnamese men and women have the highest lung cancer incidence rates, given that the prevalence of current smoking in Vietnamese women is the lowest of all Asian ethnic groups. 

Vietnamese have the lowest income and education level among the Asian ethnic groups examined. 

Korean

Koreans in California have a particularly high incidence of stomach cancer.  The incidence for Korean men is nearly twice that of Vietnamese men and over 5 times higher than that for non-Hispanic White men.  Stomach cancer incidence rates for Korean women are nearly twice as high as those for Vietnamese females and over 7 times higher than non-Hispanic females. 

Worldwide, Korea has the highest incidence of stomach cancer for males, and ranks third in the incidence of stomach cancer among females.  The unusually high rate of stomach cancer in Korea may be related to traditional dietary patterns in Korea, which include consumption of foods that are highly salted and rich in nitrites/nitrates. 

Liver cancer incidence and mortality rates among Koreans residing in California are the highest of all the Asian ethnic groups in females and second highest in males.  In Korea, the incidence of liver cancer ranks third worldwide for men and 15th for women.  This is likely related to high prevalence of hepatitis B virus infection in the Korean population.  Koreans in California also have the highest proportion who report alcohol consumption in men, 71.1%, and women, 43.4%, among all Asian ethnic groups.

Korean women have the second highest incidence and death rate from cervical cancer.  Only two thirds of Korean women reported receiving a Pap smear in the last 3 years.

Korean men have the second highest incidence and death rates from colorectal cancer, comparable to those of non-Hispanic White men.  Korean men have the highest lung cancer death rates among the Asian ethnic groups, although the incidence rate is the third largest.  About 36% of Korean men are current smokers, the highest smoking prevalence of all Asian American ethnic groups examined. 

Japanese

High incidence rates for colorectal, stomach, prostate, and breast cancer were observed for Japanese Americans relative to other Asian ethnic groups.
Colorectal cancer incidence and mortality rates for Japanese males were higher than those of every other Asian ethnic group, and even surpassed those for non-Hispanic Whites.  Japanese females also had higher incidence of colorectal cancer than all other groups, including non-Hispanic Whites. 
Diets high in processed and/or red meat and lacking sufficient intake of fruits and vegetables have been associated with increased risk of colorectal cancer.  Heavy alcohol consumption, physical inactivity, and overweight are also risk factors.

Japanese Americans exhibit a number of behavioral risk factors for colorectal and other cancers.  Most notable is the prevalence of overweight.  The prevalence of overweight for Japanese males, 52.5%, and females, 28.3%, in California was greater than any other Asian ethnic group with the exception of Filipino females.  In addition, Japanese females reported a prevalence of current smoking of 15.6%, which was higher than all other Asian ethnic groups and similar to the prevalence among non-Hispanic Whites, 15.9%.  The colorectal cancer rates in Japan are far higher than in any other Asian country, presumably reflecting changes in the Japanese dietary and behavioral patterns as a result of the Westernization of Japan. 

Dietary and behavioral factors associated with Westernization may also play a role in the high incidence of breast cancer observed for Japanese females.  Although the breast cancer incidence rate for Japanese females is lower than that of non-Hispanic White females, it is the highest of all Asian ethnic groups.  Lower age at menarche, late child bearing, fewer pregnancies, and the increased use of post menopausal therapies are all factors that are prevalent in Western countries and associated with increased risk of breast cancer. 

The incidence and mortality rates for stomach cancer were also high among Japanese Americans.  Japanese males and females in California had the third highest incidence rates and the second highest mortality rates of stomach cancer compared with all other Asian ethnic groups.  Consumption of diets high in intake of salty and nitrite/nitrate rich food as part of the traditional Japanese diet may play a role.  

COMMENT:  The fact that 44.1% of Asian Americans had acquired a bachelor’s degree in the year 2000 is a striking contrast to the proportion of Hispanic Americans who had done so, 10.4%. 

I found it almost incredible that Chinese women had the second highest incidence of lung cancer of all Asian ethnic groups since only 2.2% of them reported that they were current smokers.  Is it really possible that this high incidence of lung cancer among Chinese women is due to exposure to second hand smoke and to cooking oil at high temperatures?  Surely, something else is involved in this paradox. 

I was rather surprised at the authors’ statement that “variations in HPV infection rates and types do not appear to explain the large international variation in cervical cancer risk.”  How much do we know about the prevalence of HPV infection in such places as China, India, Colombia, and the nations of sub-Saharan Africa?  I rather suspect we really don’t know much.  I was somewhat surprised that no mention was made of the fact that having multiple sexual partners is a risk factor for acquiring the HPV virus and hence, increased risk of developing cervical cancer.  A fascinating study conducted in Israel several decades ago suggested that if wives are strictly monogamous but their husbands have multiple sexual partners, such wives are at increased risk of cervical cancer. 

Several observations regarding the Japanese are seemingly contradictory.  We read that “dietary and behavioral factors associated with Westernization may also play a role in the high incidence of breast cancer observed for Japanese females.”  A bit later we are told that the high incidence of stomach cancer among Japanese may be explained by “consumption of diets high in intake of salty and nitrite/nitrate rich foods as part of the traditional Japanese diet.” 

For many years the incidence and mortality of stomach cancer was strongly inversely correlated with social class in our country - the higher the social class, the lower the mortality from stomach cancer.  Clearly, a very large percentage of Japanese Americans are upper class and upper middle class, which doesn’t fit with the usual pattern.