Educational inequalities and premature mortality: the Cuba Prospective Study

BACKGROUND

Although socioeconomic status is a major determinant of premature mortality in many populations, the impact of social inequalities on premature mortality in Cuba, a country with universal education and health care, remains unclear. We aimed to assess the association between educational level and premature adult mortality in Cuba.

METHODS

The Cuba Prospective Study (a cohort study) enrolled 146 556 adults aged 30 years and older from the general population in five provinces from Jan 1, 1996, to Nov 24, 2002. Participants were followed up until Jan 1, 2017, for cause-specific mortality. Deaths were identified through linkage to the Cuban Public Health Ministry's national mortality records. Cox regression models yielded rate ratios (RRs) for the effect of educational level (a commonly used measure for social status) on mortality at ages 35-74 years, with assessment for the mediating effects of smoking, alcohol consumption, and BMI.

FINDINGS

A total of 127 273 participants aged 35-74 years were included in the analyses. There was a strong inverse association between educational level and premature mortality. Compared with a university education, men who did not complete primary education had an approximately 60% higher risk of premature mortality (RR 1·55, 95% CI 1·40-1·72), while the risk was approximately doubled in women (1·96, 1·81-2·13). Overall, 28% of premature deaths could be attributed to lower education levels. Excess mortality in women was primarily due to vascular disease, while vascular disease and cancer were equally important in men. 31% of the association with education in men and 18% in women could be explained by common modifiable risk factors, with smoking having the largest effect.

INTERPRETATION

This study highlights the value of understanding the determinants of health inequalities in different populations. Although many major determinants lie outside the health system in Cuba, this study has identified the diseases and risk factors that require targeted public health interventions, particularly smoking.

FUNDING

UK Medical Research Council, British Heart Foundation, Cancer Research UK, CDC Foundation (with support from Amgen).

Body-mass index, blood pressure, diabetes and cardiovascular mortality in Cuba: prospective study of 146,556 participants

BACKGROUND

Cardiovascular disease accounts for about one-third of all premature deaths (ie, age < 70) in Cuba. Yet, the relevance of major risk factors, including systolic blood pressure (SBP), diabetes, and body-mass index (BMI), to cardiovascular mortality in this population remains unclear.

METHODS

In 1996-2002, 146,556 adults were recruited from the general population in five areas of Cuba. Participants were interviewed, measured (height, weight and blood pressure) and followed up by electronic linkage to national death registries until Jan 1, 2017; in 2006-08, 24,345 participants were resurveyed. After excluding all with missing data, cardiovascular disease at recruitment, and those who died in the first 5 years, Cox regression (adjusted for age, sex, education, smoking, alcohol and, where appropriate, BMI) was used to relate cardiovascular mortality rate ratios (RRs) at ages 35-79 years to SBP, diabetes and BMI; RR were corrected for regression dilution to give associations with long-term average (ie, 'usual') levels of SBP and BMI.

RESULTS

After exclusions, there were 125,939 participants (mean age 53 [SD12]; 55% women). Mean SBP was 124 mmHg (SD15), 5% had diabetes, and mean BMI was 24.2 kg/m2 (SD3.6); mean SBP and diabetes prevalence at recruitment were both strongly related to BMI. During follow-up, there were 4112 cardiovascular deaths (2032 ischaemic heart disease, 832 stroke, and 1248 other). Cardiovascular mortality was positively associated with SBP (>=120 mmHg), diabetes, and BMI (>=22.5 kg/m2): 20 mmHg higher usual SBP about doubled cardiovascular mortality (RR 2.02, 95%CI 1.88-2.18]), as did diabetes (2.15, 1.95-2.37), and 10 kg/m2 higher usual BMI (1.92, 1.64-2.25). RR were similar in men and in women. The association with BMI and cardiovascular mortality was almost completely attenuated following adjustment for the mediating effect of SBP. Elevated SBP (>=120 mmHg), diabetes and raised BMI (>=22.5 kg/m2) accounted for 27%, 14%, and 16% of cardiovascular deaths, respectively.

CONCLUSIONS

This large prospective study provides direct evidence for the effects of these major risk factors on cardiovascular mortality in Cuba. Despite comparatively low levels of these risk factors by international standards, the strength of their association with cardiovascular death means they nevertheless exert a substantial impact on premature mortality in Cuba.

Alcohol consumption and cause-specific mortality in Cuba: prospective study of 120 623 adults

BACKGROUND

The associations of cause-specific mortality with alcohol consumption have been studied mainly in higher-income countries. We relate alcohol consumption to mortality in Cuba.

METHODS

In 1996-2002, 146 556 adults were recruited into a prospective study from the general population in five areas of Cuba. Participants were interviewed, measured and followed up by electronic linkage to national death registries until January 1, 2017. After excluding all with missing data or chronic disease at recruitment, Cox regression (adjusted for age, sex, province, education, and smoking) was used to relate mortality rate ratios (RRs) at ages 35-79 years to alcohol consumption. RRs were corrected for long-term variability in alcohol consumption using repeat measures among 20 593 participants resurveyed in 2006-08.

FINDINGS

After exclusions, there were 120 623 participants aged 35-79 years (mean age 52 [SD 12]; 67 694 [56%] women). At recruitment, 22 670 (43%) men and 9490 (14%) women were current alcohol drinkers, with 15 433 (29%) men and 3054 (5%) women drinking at least weekly; most alcohol consumption was from rum. All-cause mortality was positively and continuously associated with weekly alcohol consumption: each additional 35cl bottle of rum per week (110g of pure alcohol) was associated with ∼10% higher risk of all-cause mortality (RR 1.08 [95%CI 1.05-1.11]). The major causes of excess mortality in weekly drinkers were cancer, vascular disease, and external causes. Non-drinkers had ∼10% higher risk (RR 1.11 [1.09-1.14]) of all-cause mortality than those in the lowest category of weekly alcohol consumption (<1 bottle/week), but this association was almost completely attenuated on exclusion of early follow-up.

INTERPRETATION

In this large prospective study in Cuba, weekly alcohol consumption was continuously related to premature mortality. Reverse causality is likely to account for much of the apparent excess risk among non-drinkers. The findings support limits to alcohol consumption that are lower than present recommendations in Cuba.

FUNDING

Medical Research Council, British Heart Foundation, Cancer Research UK, CDC Foundation (with support from Amgen).

Association of childhood smoking and adult mortality: prospective study of 120 000 Cuban adults

BACKGROUND

The average age at which people start smoking has been decreasing in many countries, but insufficient evidence exists on the adult hazards of having started smoking in childhood and, especially, in early childhood. We aimed to investigate the association between smoking habits (focusing on the age when smokers started) and cause-specific premature mortality in a cohort of adults in Cuba.

METHODS

For this prospective study, adults were recruited from five provinces in Cuba. Participants were interviewed (data collected included socioeconomic status, medical history, alcohol consumption, and smoking habits) and had their height, weight, and blood pressure measured. Participants were followed up until Jan 1, 2017 for cause-specific mortality; a subset was resurveyed in 2006-08. We used Cox regression to calculate adjusted rate ratios (RRs) for mortality at ages 30-69 years, comparing never-smokers with current smokers by age they started smoking and number of cigarettes smoked per day and with ex-smokers by the age at which they had quit.

FINDINGS

Between Jan 1, 1996, and Nov 24, 2002, 146 556 adults were recruited into the study, of whom 118 840 participants aged 30-69 years at recruitment contributed to the main analyses. 27 264 (52%) of 52 524 men and 19 313 (29%) of 66 316 women were current smokers. Most participants reported smoking cigarettes; few smoked only cigars. About a third of current cigarette smokers had started before age 15 years. Compared with never-smokers, the all-cause mortality RR was highest in participants who had started smoking at ages 5-9 years (RR 2·51, 95% CI 2·21-2·85), followed by ages 10-14 years (1·83, 1·72-1·95), 15-19 years (1·56, 1·46-1·65), and ages 20 years or older (1·50, 1·39-1·62). Smoking accounted for a quarter of all premature deaths in this population, but quitting before about age 40 years avoided almost all of the excess mortality due to smoking.

INTERPRETATION

In this cohort of adults in Cuba, starting to smoke in childhood was common and quitting was not. Starting in childhood approximately doubled the rate of premature death (ie, before age 70 years). If this 2-fold mortality RR continues into old age, about half of participants who start smoking before age 15 years and do not stop will eventually die of complications from their habit. The greatest risks were found among adults who began smoking before age 10 years.

FUNDING

UK Medical Research Council, Cancer Research UK, British Heart Foundation, US Centers for Disease Control and Prevention (CDC) Foundation (with support from Amgen).

[Quality of maternal mortality statistics in Cuba, 2013Qualidade das estatísticas de mortalidade materna em Cuba, 2013]

Objetivos

Evaluar el grado de integridad del registro estadístico cubano de muertes maternas y la calidad de la clasificación de las causas de muerte recogidas en ese registro.

Métodos

Se analizó la información de todas las cubanas fallecidas en edad fértil en el año 2013 según el registro continuo de mortalidad de la Dirección de Registros Médicos y Estadísticas de Salud del Ministerio de Salud Pública de Cuba (MINSAP), independientemente de la causa básica de muerte consignada. Cuatro grupos de investigación (nacional, de expertos, provincial y de unidades de salud), con funciones definidas, aplicaron cuatro formularios para determinar si hubo embarazo en el año previo a la defunción, reevaluar si los casos correspondían a una muerte materna y, en ese caso, revisar la clasificación.

Resultados

Se investigaron las 2 731 mujeres fallecidas en edad reproductiva notificadas en Cuba en el 2013; de ellas las causas de muerte de 2 711 (99,3%) resultaron concluyentes y, de estas, 97 (3,6%) habían tenido un embarazo en el año previo a la defunción. Se encontraron 50 muertes maternas (una más que en el registro continuo) para 2% de error y un factor de ajuste de 1,02. De las 97 muertes estudiadas, solo se reclasificaron 4 casos: 2 muertes maternas y 1 muerte relacionada con el embarazo, el parto y el puerperio, según el registro continuo, que se reclasificaron como muertes directas, y 1 muerte considerada no materna por el registro continuo que se reclasificó como muerte materna tardía, para una concordancia de 95,9%.

Conclusiones

La información sobre las muertes maternas recogida en el registro continuo de mortalidad del MINSAP tiene un alto nivel de integridad. La calidad de la clasificación de las muertes maternas en ese registro es elevada, al existir muy pocos cambios en la reclasificación de las causas de muerte.

Burden of hypertension and associated risks for cardiovascular mortality in Cuba: a prospective cohort study

BACKGROUND

In Cuba, hypertension control in primary care has been prioritised as a cost-effective means of addressing premature death from cardiovascular disease. However, there is little evidence from large-scale studies on the prevalence and management of hypertension in Cuba, and no direct evidence of the expected benefit of such efforts on cardiovascular mortality.

METHODS

In a prospective cohort study, adults in the general population identified via local family medical practices were interviewed between Jan 1, 1996, and Nov 24, 2002, in five areas of Cuba, and a subset of participants were resurveyed between July 14, 2006, and Oct 19, 2008, in one area. During household visits, blood pressure was measured and information obtained on diagnosis and treatment of hypertension. We calculated the prevalence of hypertension (systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg, or receiving treatment for hypertension) and the proportion of people with hypertension in whom it was diagnosed, treated, and controlled (systolic blood pressure <140 mm Hg, diastolic blood pressure <90 mm Hg). Deaths were identified through linkage by national identification numbers to the Cuban Public Health Ministry records, to Dec 31, 2016. We used Cox regression analysis to compare cardiovascular mortality between participants with versus without uncontrolled hypertension. Rate ratios (RRs) were used to estimate the fraction of cardiovascular deaths attributable to hypertension.

FINDINGS

146 556 participants were interviewed in the baseline survey in 1996-2002 and 24 345 were interviewed in the resurvey in 2006-08. After exclusion for incomplete data and age outside the range of interest, 136 111 respondents aged 35-79 years (mean age 54 [SD 12] years; 75 947 [56%] women, 60 164 [44%] men) were eligible for inclusion in the analyses. 34% of participants had hypertension. Among these, 67% had a diagnosis of hypertension. 76% of participants with diagnosed hypertension were receiving treatment and blood pressure was controlled in 36% of those people. During 1·7 million person-years of follow-up there were 5707 cardiovascular deaths. In the age groups 35-59, 60-69, and 70-79 years, uncontrolled hypertension at baseline was associated with RRs of 2·15 (95% CI 1·88-2·46), 1·86 (1·69-2·05), and 1·41 (1·32-1·52), respectively, and accounted for around 20% of premature cardiovascular deaths.

INTERPRETATION

In this Cuban population, a third of people had hypertension. Although levels of hypertension diagnosis and treatment were commensurate with those in some high-income countries, the proportion of participants whose blood pressure was controlled was low. As well as reducing hypertension prevalence, improvement in blood pressure control among people with diagnosed hypertension is required to prevent premature cardiovascular deaths in Cuba.

FUNDING

Medical Research Council, British Heart Foundation, Cancer Research UK.