SEYLL by main broad cause groups
During 2010, an overall number of 41,887 (female 44.4%; male 55.6%) deaths were registered in Hong Kong, resulting in 524,706.5 years lost due to premature death, with 41.7% and 58.3% of the SEYLL attributable to female and male deaths, respectively. Overall, the highest percentages of SEYLL were estimated for group II conditions, representing 78.8% of the total disease burden. Group I and III conditions share 12.7% and 8.5%, respectively (Table 1).
The female population showed a higher share for group II conditions, with 80% as compared to the male population (78%). Group I conditions accounted for 12.7% of the SEYLLs for both males and females. Men showed a higher percentage attributable to injuries at 9.3% in comparison to 7.3% for women.
Figure 1 shows SEYLL shares for the three condition groups stratified by age group. With a share of 46.6% of the total burden at the age group 0–1, group I conditions reach their maximum SEYLL share. The percentage shows a decreasing trend with two smaller peaks of 13.6% and 8.8% in the age-groups 20–24 and 30–34 years, respectively. After a constant phase at about 6%, an increase was identified beginning in the age-group 55–59 years reaching a peak in the age-group 85+ (28.1%).
Group II conditions presented the lowest observed SEYLL shares in the age-group 25–29 years, with 37.4%. The SEYLL due to group II conditions appeared to increase with age, reaching a peak at 87.5% (age-group 60–64).
For group III conditions, a constant rise of the SEYLL share is observed starting in age-group 0, reaching a peak of 57.5% in age-group 25–29 years, dropping rapidly at 45–49 years (10.6%), and then flattening out with increasing age.
The overall SEYLL-rate per year for the male population (9,289 SEYLL/100,000) exceeded the female rate (5,863 SEYLL/100,000) 1.6-fold. SEYLL-rates for group I and II conditions were higher for the male population, especially in the age-group 0–1 with 11,303.4 SEYLL/100,000 and 11,608.9 SEYLL/100,000 as compared to a female SEYLL-rate of 7,807.5 SEYLL/100,000 and 8,708.3 SEYLL/100,000, respectively (Figure 2). After the age group 0–1 year, group I and II rates for both males and females showed a decreasing trend and remained at a constantly low level followed by an upswing of rates. Even though the rates of group I conditions in the population above 45 years increased for both sexes, the trend for males and females was initially diverging, with male rates presenting a steeper slope, reaching a peak of 13,909.8 SEYLL/100,000 in the age-group 85+, which is 1.2-fold higher than for females (11,724 SEYLL/100,000). For group II conditions, a similar trend could be observed, with very high SEYLL-rates for children aged 0–1 year and subsequent low levels until the age-group of 30–34 years. With further increasing age, the SEYLL-rates for group II conditions rose with a steeper slope for males, reaching a maximum of 34,002.5 SEYLL/100,000 in the age-group 80–84 years. The females showed a maximum of 30,403.3 SEYLL/100,000, which was delayed to the age group of 85+. For all age-groups (except age-group 5–10 years) the male population showed an increased SEYLL-rate due to group III conditions as compared to the female population. The peak was reached at 25–29 years of age with 1,656.7 SEYLL/100,000. In this age group the SEYLL-rate for men was 3.6 times higher than the one estimated for women. SEYLL for group III conditions decreased with age but presented smaller peaks in the age groups 75–79 and 80–84 years for females and males, respectively.
SEYLL by condition groups
At the first level of disaggregation (Table 2), malignant neoplasms (39.1%), cardiovascular diseases (21.7%) and respiratory infections (8.9%) were the leading cause groups, together accounting for about 70% of the years of life lost due to premature death. Stratification by sex led to similar leading condition groups.
The top three leading single disease causes of SEYLL were “trachea, bronchus and lung cancers”, “ischaemic heart disease” and “lower respiratory infections”, together accounting for 28.6% of the overall SEYLL in Hong Kong. Stratified by sex, the three leading causes of SEYLL remained the same but differed in their order (Figure 3). For women, lower respiratory infections (529.1 SEYLL/100,000) were the leading cause, followed by ischaemic heart disease (484.6 SEYLL/100,000) and trachea, bronchus and lung cancers (480.1 SEYLL/100,000) (Figure 3). Women were further strongly affected by breast cancer (ranked 5th) and nephritis and nephrosis (ranked 9th), but these entities were not among the ten leading causes of SEYLL for men. The leading cause for men was trachea, bronchus and lung cancers (1,042.3 SEYLL/100,000), followed by ischaemic heart disease (1,016.0 SEYLL/100,000) and lower respiratory infections (812.6 SEYLL/100,000). Furthermore, liver cancer (ranked 4th), chronic obstructive pulmonary disease (ranked 8th) and mouth and oropharynx cancer (ranked 9th) were conditions that were important drivers of SEYLL for men but did not belong to the ten leading causes of SEYLL for women.
The SEYLL-rates for the male population were generally higher for all conditions (Figure 3), especially for ischaemic heart disease, trachea, bronchus and lung cancers, and liver cancer, with rates for males being 2.1, 2.2 and 3.5 times higher than the female rates, respectively. An exception of course was breast cancer, a sex-specific malignant neoplasm mainly occurring in the female population.
The overall leading causes include many malignant neoplasms, which constituted five out of ten leading causes. It is noteworthy that the group III condition self-inflicted injuries strongly affected both sexes and was ranked 6th and 7th in the male and female leading causes, respectively.
Figure 4 presents the SEYLL for the six leading causes stratified by age and sex, highlighting the age-groups most affected by the presented conditions. Trachea, bronchus and lung cancers showed the highest rates for the population aged above 30 years, reaching a maximum of 4,362.8 SEYLL/100,000 for men aged 70–74 years and 2,043.4 for women aged 75–79 years, with rates being 2.2- to 3-fold higher for the male population. Cerebrovascular and ischaemic heart diseases showed similar trends with a steady increase in SEYLL-rates starting at age 30. A major sex-difference was observed during the age-span between 30–59 years, with higher cerebrovascular SEYLL-rates for the female population. A reversing trend was observed thereafter with male SEYLL-rates exceeding those of the female and peaking in the age-group 85+ with 2,529.9 SEYLL/100,000 compared to 1,496.8 SEYLL/100,000 for women. Lower respiratory infections (ranked 3rd) strongly affected the elderly population, reaching the maximum rates of 12,149.5 SEYLL/100,000 and 10,249.4 SEYLL/100,000 for men and women in the age-group of 85 years and older, respectively. In contrast, self-inflicted injuries strongly affected the younger population aged 15–44 years with maxima of 1,288.6 SEYLL/100,000 for men (age-group 25–29) and 493 SEYLL/100,000 for women (age-group 30–34), respectively. At later ages, these rates declined for both sexes until the age-group 65–69 but increased again with a peak at age-group 75–79 years. SEYLL-rates for colon and rectum cancers presented typical patterns for malignant neoplasms, affecting the population in the second half of the life-span with highest rates observed for the population aged 80–84, with 2,084.7 SEYLL/100,000 for males and 1,891.6 SEYLL/100,000 for females.
The majority of single leading causes (except self-inflicted injuries) showed high concentrations of SEYLL in the later stages of life.
Time discounting and age-weighting effects
Three additional scenarios were used to demonstrate the effects of time-discounting and age-weighting on the disease burden due to premature death (Figure 5). Scenario one (3,1) resulted in the lowest modulated SEYLL, with a decrease of the overall disease burden by 51.6% compared to the baseline scenario (0,0). The highest decrease was observed for group I conditions, with a reduction of 55.1%. Scenario two (3,0) resulted in the highest modulated SEYLL, with an overall decrease of 25.5% as compared to the baseline scenario, with the highest reductions observed for group III conditions (−39.8%). Scenario three (0,1) showed intermediate modulated SEYLL, with a decrease of total SEYLL by 33.7% compared to the baseline estimates. The strongest reductions were found for group I conditions (−38%) (see Additional file 1 for detailed information).
Major changes in leading causes of premature death were observed for scenario three (0,1). Considering higher age-weights for the productive age groups, conditions occurring in earlier stages of life, and in particular self-inflicted injuries, received an upturn in priority ranking from 5th to 3rd position, even exceeding lower respiratory infections (data not shown).
Local Hong Kong life-expectancy
Sensitivity analyses using local Hong Kong standard life-expectancy indicated considerable changes of SEYLL, especially for the female population (Additional file 2). Using the Hong Kong standard, female remaining life-expectancy at birth was 3.5 years longer than the WHO standard. The remaining Hong Kong life-expectancy for men was nearly identical at birth but slightly higher with increasing age. Altering the life-expectancy resulted in an increase of total SEYLL of 10.8% (15.1% for female; 7.4% for male). In particular, SEYLL due to group I conditions for the female population increased by 18.6%.
The strongest impact of prolonged life-expectancy was identified for women aged 60 and older, with total SEYLL-rates per 100,000 being between 1.1 and 1.3 times higher as compared to the baseline (Figure 6). For men, the highest SEYLL-rate ratios were observed at age 70 and onwards, with SEYLL-rates being between 1.1 and 1.25 times higher than the WHO standard scenario.
SEYLL trends over time
In total, the disease burden due to premature mortality increased remarkably between 2001 and 2010, by 6.4% (2001: 491,211 SEYLL; 2010: 524,706 SEYLL). Taking into account changes in the population (e.g. population growth), total SEYLL-rates per 100,000 population increased from 7,315.9 SEYLL/100,000 (2001) to 7,470 SEYLL/100,000 (2010). The strongest increase was observed for the male population, with a rise from 9,010.4 SEYLL/100,000 in 2001 to 9,289.1 SEYLL/100,000 in 2010. At the first level of disaggregation, an upturn of SEYLL due to group I and II conditions was identified for the male population, with SEYLL-rates for group I conditions being 1.4-fold higher in 2010 (Table 3). In contrast, a downturn of 27% of SEYLL-rates for group III conditions among males was observed. The total disease burden for women remained constant over the period. However, a considerable increase was identified for SEYLL-rates due to group I conditions, which in 2010 were 1.4-fold higher. Group II conditions remained constant and SEYLL-rates due to group III conditions decreased by 22% over the same time period.