This study provides additional evidence that previous pulmonary tuberculosis and chronic bronchitis/emphysema are causally related to lung cancer, although the precise mechanism is still unclear. The results for asthma and pneumonia, while suggestive of a positive association, did not reach the traditional level of statistical significance and should be interpreted with caution.

No abstract

A recent analysis showed that the excess odds ratio (EOR) for lung cancer due to smoking can be modeled by a function which is linear in total pack-years and exponential in the logarithm of smoking intensity and its square. Below 15-20 cigarettes per day, the EOR/pack-year increased with intensity (direct exposure rate or enhanced potency effect), suggesting greater risk for a total exposure delivered at higher intensity (for a shorter duration) than for an equivalent exposure delivered at lower intensity. Above 20 cigarettes per day, the EOR/pack-year decreased with increasing intensity (inverse exposure rate or reduced potency effect), suggesting greater risk for a total exposure delivered at lower intensity (for a longer duration) than for an equivalent exposure delivered at higher intensity. The authors applied this model to data from 10 case-control studies of cancer, including cancers of the lung, bladder, oral cavity, pancreas, and esophagus. At lower intensities, there was enhanced potency for several cancer sites, but narrow ranges for pack-years increased uncertainty, precluding definitive conclusions. At higher intensities, there was a consistent reduced potency effect across studies. The intensity effects were statistically homogeneous, indicating that after accounting for risk from total pack-years, intensity patterns were comparable across the diverse cancer sites.

There are suggestions that women have higher relative risks of lung cancer than men given similar levels of tobacco exposure, implying that sex-related hormones may influence lung cancer risk. We evaluated the association between lung cancer risk and menstrual and reproductive factors on a subset of self-responding females in a population based case-control study in Eastern Gansu Province, China, 1994-1998. The analysis included 109 incident lung cancer cases and 435 controls selected from the census list and frequency matched to cases on age and prefecture. Odds ratios were lower for later ages at menarche (trend, P = 0.015) and later ages at menopause (trend, P = 0.074). Despite limitations, these findings suggest a possible role of hormones in the etiology of lung cancer in females.

Thyroid nodularity following continuous low-dose radiation exposure in China was determined in 1,001 women aged 50-65 years who resided in areas of high background radiation (330 mR/yr) their entire lives, and in 1,005 comparison subjects exposed to normal levels of radiation (114 mR/yr). Cumulative doses to the thyroid were estimated to be of the order of 14 cGy and 5 cGy, respectively. Personal interviews and physical examinations were conducted, and measurements were made of serum thyroid hormone levels, urinary iodine concentrations, and chromosome aberrations in circulating lymphocytes. For all nodular disease, the prevalences in the high background and control areas were 9.5% and 9.3%, respectively. For single nodules, the prevalences were 7.4% in the high background area and 6.6% in the control area (prevalence ratio = 1.13; 95% confidence interval = 0.82-1.55). There were no differences found in serum levels of thyroid hormones. Women in the high background region, however, had significantly lower concentrations of urinary iodine and significantly higher frequencies of stable and unstable chromosome aberrations. Increased intake of allium vegetables such as garlic and onions was associated with a decreased risk of nodular disease, which seems consistent with experimental studies suggesting that allium compounds can inhibit tumor growth and proliferation. The prevalence of mild diffuse goiter was higher in the high background radiation region, perhaps related to a low dietary intake of iodine. These data suggest that continuous exposure to low-level radiation throughout life is unlikely to appreciably increase the risk of thyroid cancer. However, such exposure may cause chromosomal damage.

Incomplete combustion of coal in homes has been linked with lung cancer in China. We report on a lung cancer case-control study in a rural area of China, where many residents live in underground dwellings and burn coal and unprocessed biomass (crop residues, wood, sticks, and twigs) for heating and cooking. We interviewed 846 patients with lung cancer (626 men, 220 women; aged 30 to 75 years) diagnosed between 1994 and 1998, and 1740 population-based controls. The odds ratio for lung cancer associated with coal use compared with that for biomass in the house of longest residence was 1.29 (95% confidence interval, 1.03 to 1.61), adjusted for smoking and socioeconomic status. The risk for lung cancer increased relative to the percentage of time that coal was used over the past 30 years (P = 0.02). Our findings suggest that coal may contribute to the risk of lung cancer in this rural area of China.

No abstract

We report results from a population‐based case‐control study of lung cancer and environmental tobacco smoke (ETS) among never‐smokers conducted in 2 rural prefectures of China, including 200 female and 33 male lung cancer cases, and 407 female and 114 male controls, matched on age, sex and prefecture of current residence. The odds ratio (OR) for ever‐exposed to ETS was 1.19 (95% CI 0.7–2.0), with a significant trend (p<0.05) with increasing exposure. ORs were 1.00, 1.04, 1.13 and 1.51 for non‐exposed, <10, 10–19 and ≥20 pack‐years of ETS exposure, respectively. Excess risks were limited to ETS exposures in childhood (≤18 years of age). The OR for ever‐exposed to ETS in childhood, adjusting for ETS exposure in adulthood, was 1.52 (95% CI 1.1–2.2), with a significant trend (p<0.01) with increasing pack‐years of childhood exposure, 1.00, 1.43, 1.81 and 2.95, respectively. After adjustment for ETS in childhood, there was no excess risk from adult ETS exposure. The OR for ever‐exposed to ETS in adulthood was 0.90 (95% CI 0.–1.4). These results were not affected by adjustment for type of residential dwelling, type or amount of fuel used, perceived indoor smokiness, or measures of socioeconomic status, or omitting next‐of‐kin respondents. Int. J. Cancer 88:139–145, 2000. © 2000 Wiley‐Liss, Inc.