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Dear Sir,

As tobacco smoking has long been established as the principal cause of lung cancer, the divergent trends in lung cancer mortality across different countries are mainly related to the prevalence of cigarette smoking. In women, there are unambiguous upsurges in the rates in almost all European Union countries, with the exceptions being the United Kingdom and Ireland, where lung cancer rates are now declining.1 Using an age-period-cohort model, with data up to 1997, we previously reported that the smoking-related lung-cancer epidemic among Spanish women was still at an early stage.2 In spite of the rise in the prevalence of female smokers during the last decades, increasing mortality rates were evident only among younger generations. Overall standardised mortality rates were misleadingly low (6.3 per 100,000 in 1973 and 6.4 in 1997), creating a false impression as if they were hardly affected by cigarette smoking. A descriptive study with data up to 2002 is reported in this paper to show the impact of smoking duration, delayed by several decades, on the overall mortality rates, which now actually indicates the beginning of the lung-cancer epidemic among Spanish women.

Data on lung-cancer mortality (code 162 of the International Classification of Diseases) and population figures were obtained from the Spanish National Institute of Statistics. Age-specific mortality rates were calculated for every 5-year age group between 35 and 74 years, and overall age-standardised mortality rates were produced using the direct method according to the age structure of the Spanish population of 1980. A regression equation on the natural logarithm of the rates was used to calculate the trends. The coefficient B (slope) with a 95% confidence interval (CI) of the best-fitting linear regression line was considered the mean annual percentage of variation.

Table I shows the total percentage of variation in age-specific rates for the period 1997–2002. The most significant increases were found in groups aged 59 years and younger, ranging from 14.9% among 40- to 44-year-olds to 61.7% among 50- to 54-year-olds. By comparison, the increases in all groups aged 60 years and older were under 10%. The overall standardised mortality rate was 6.4 per 100,000 population in 1997, hardly different from that in 1973 when the rate was 6.3. However, from 1997 the rate increased by 18.8%, reaching 7.6 per 100,000 in 2002 (Fig. 1), with an average annual increase of 3.2% (95% CI 2.3–4.0). A moderate rise of 1.3% (95% CI 0.9–1.8) annually was seen during the preceding period 1988–96.

Table I. Trends in Age-Specific Mortality Rates for Spanish Women: 1997–2002
Age groupRate (105)Total change (%)
19972002
35–392.403.10+29.2
40–444.785.49+14.9
45–496.269.67+54.5
50–547.8612.71+61.7
55–5910.0114.44+44.3
60–6414.5815.59+6.9
65–6919.6121.46+9.4
70–7425.9227.88+7.6
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Figure 1. Age-standardised lung-cancer mortality rates for Spanish women, from 1973–2002.

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These results show the beginning of a rapidly rising lung cancer mortality phase in the epidemic curve, which actually began in 1997. After a moderate rise from 1988, overall standardised mortality rates now clearly exceed those previously reached in the late 70s and begin a sharper increase. A similar change in the rates, but three decades before, was seen in the United States3 where the rapid increase in mortality started from rates about 6 per 100,000 (adjusted to 1970 population). Compared with other developed countries, the approximate 30-year delay in the beginning of the tobacco-related lung cancer epidemic among Spanish women can be explained by social factors. Because of strong cultural prohibitions, it was not until the 1970s when smoking became widespread among women in Spain. The rapid increase in female smoking after 1970 coincided with aggressive tobacco industry marketing practices, which exploited a period of social liberalisation.4

If smoking habits and hence the lung cancer epidemic for Spanish women follow the same pattern as in other developed countries, mortality rates will continue to rise for several decades, as the increases spread to older age groups. However, the percentage of smokers and therefore the rates are not expected to reach those of men. After a continuous increase, the prevalence of smoking women aged 16 years and older5, 6 did not change from 1995 to 2001, levelling off at about 27%. Moreover, data from the last survey7 indicates a decrease to 24.7% in 2003. In men, on the contrary, the percentage of smokers steadily decreased from 64% in 1978 to 37.6% in 2003, and lung cancer mortality rates peaked at 60.8 per 100,000 in 1995.

Recent recommendations with the imperative that anti-tobacco strategies urgently target women living in the European Union1, 8 especially makes sense in Spain, where lung cancer mortality rates are still low. Although increased risk for lung cancer among former smokers remains up to 30 years after smoking cessation, a 50% or greater risk reduction in the first decade of smoking abstinence for female former smokers compared with current smokers has been observed.9 Thus, even though the epidemic will not halt owing to the long latency interval between the onset of smoking and the development of lung cancer, the increasing number of lung cancer deaths among Spanish females might be mitigated provided a significant reduction in the prevalence of smoking women.

To conclude, the rapidly increasing mortality phase in the Spanish female lung cancer epidemic curve has already begun and unfortunately will continue for some decades. Authorities in Spain should urgently implement anti-tobacco strategies, specifically addressed to women in order to prevent to some extent the coming tobacco-related excess of lung cancer deaths.

References

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    Bray F, Tyczynski JE, Parkin DM. Going up or coming down? The changing phases of the lung cancer epidemic from 1967 to 1999 in the 15 European Union countries. Eur J Cancer 2004; 40: 96125.
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    Franco J, Pérez-Hoyos S, Plaza P. Changes in lung-cancer mortality trends in Spain. Int J Cancer 2002; 97: 1025.
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    Bilello KS, Murin S, Matthay RA. Epidemiology, etiology, and prevention of lung cancer. Clin Chest Med 2002; 23: 125.
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    Shafey O, Fernández E, Thun M, Schiaffino A, Dolwick S, Cokkinides V. Cigarette advertising and female smoking prevalence in Spain, 1982–1997. Cancer 2004; 100: 17449.
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    Regidor E, Cuenca E, García P, Gutiérrez JL, Rodríguez M. Indicadores de salud. Elaboración de los indicadores propuestos para el seguimiento del progreso hacia la Salud Para Todos en la región europea. Madrid: Ministerio de Sanidad y Consumo, 1990.
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    Ministerio de Sanidad y Consumo. Encuestas Nacionales de Salud 1987, 1993, 1995, 1997 y 2001. Madrid: Ministerio de Sanidad y Consumo, 1989, 1995, 1997, 1999, 2004.
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    Ministerio de Sanidad y Consumo. Encuesta Nacional de Salud 2003. Available from: Instituto Nacional de Estadística, URL: http://www. ine.es/inebase/ [accessed June 14, 2005].
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    Levi F, Lucchini F, Negri E, Boyle P, La Vecchia C. Cancer mortality in Europe, 1995–1999, and an overview of trends since 1960. Int J Cancer 2004; 110: 15569.
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    Ebbert JO, Yang P, Vachon CM, Vierkant RA, Cerhan JR, Folsom AR, Sellers TA. Lung cancer risk reduction after smoking cessation: observations from a prospective cohort of women. J Clin Oncol 2003; 21: 9216.

José Franco, Julio Marín.