The TRELONG study investigated genetic and environmental factors in longevity. The homozygous A-allele genotype of rs2229765 polymorphism of the IGF-1R gene was found to be a positive predictor of survival in men compared to the G/G genotype, which was confirmed by multivariate regression analysis. This study is the only available prospective study that supports the pro-surviving effect of the A/A homozygous genotype, at least in men.Circulating IGF-1 levels did not correlate with survival in our analysis. However, the significance of a low level of IGF-1 for survival is debated [34,35]. While reducing low IGF-1 levels may counteract cancer, it is associated with an increased risk of all-cause mortality and cardiovascular disease [36,37]. Additionally, a low level alone might be inadequate as a predictor of survival, as reported by Maggio et al. in another Italian population of elderly men, where IGF-1, testosterone, and dehydroepiandrosterone sulfate (DHEA-S) were evaluated; they found a cumulative negative effect on survival for these anabolic hormones [38]. Our data on IGF-1 may be inconclusive due to the lack of multiple hormone assessment. We also addressed the contribution of an inflammatory pathway to longevity. Since aging involves chronic increases in pro-inflammatory molecules, which is particularly evident for men and partly under genetic control [39], we looked for a sex-specific pattern in biochemical or genetic elements related to IL-6. Our prospective approach found that the plasma IL-6 level influenced survival more in men, and no genetic contribution was found from the polymorphism rs1800795. However, we cannot exclude that a fuller genetic investigation of the IL-6 promoter region might uncover additional genetic variability correlating with male or female expression (expressed in quartiles). We obtained four groups whose main demographic and clinical features are summarized in Table III. A high level of IL-6 was associated with increased disability and co-morbidity, while high IGF-1 was associated with an increased percentage of cancer in association with low IL-6 only. We considered the group with low IL-6 and high IGF-1 (that had an apparent reduced rate of mortality) as reference and plotted a survival curve for the entire population classified according to Table III.

Table III: Classification of the TRELONG population according to circulating levels of IGF-1 and IL-6. The p-value was calculated from a chi-square test for binary variables and ANOVA for continuous variables. CVD: cardiovascular disease (including myocardial infarction, ischemic cardiopathy, peripheral vasculopathy, and chronic heart failure); VC: vascular cerebral disease (including stroke and cerebral vasculopathies); CCI: Charlson's comorbidity index.

| High IGF-1 and low IL-6 | Low IGF-1 and low IL-6 | High IGF-1 and high IL-6 | Low IGF-1 and high IL-6 | Overall |
|--------------------------|-------------------------|--------------------------|-------------------------|--------|
| Age (mean) 82.68        | 86.13                   | 85.81                    | 88.48                   | 84.13  | 0.000  |
| Women (%) 52.30         | 55.67                   | 48.04                    | 71.88                   | 53.44  | 0.116  |
| BMI (mean) 25.14        | 24.09                   | 24.76                    | 24.23                   | 24.77  | 0.127  |
| VC(%) 14.80             | 20.62                   | 18.63                    | 9.38                    | 15.57  | 0.339 |
| CVD (%) 24.67           | 24.74                   |32.35                     |21.88                    |25.6    |0.426 |
| Cholesterol (total, mean)223.50|210.70            |206.30                    |180.50                   |213.8   |0.000  |
| Diabetes (%) 15.46      | 18.56                   |17.65                     |15.62                    |15.57   |0.884  |
| Cancer (%) 20.07        | 8.25                    |11.76                     |12.50                    |16.92   |0.021  |
| ADL (mean) 5.32         | 4.88                    |4.57                      |4.13                     |5.002   |0.000  |
| CCI (mean) 5.59         | 5.85                    |6.16                      |6.25                     |5.766   |0.005  |
| Smoking (%) 41.58       |42.71                    |41.58                     |25.00                    |41.17   |0.293  |
| noking (%)IL-6 (pg/mL)41.58|42.71                 ||25.00                    ||        ||

IGF-1 and IL-6 level scatterplot

TotalAt year [missing information], the Istituto Nazionale di Statistica (Istat) published a report in Rome, Italy by the Servizio Popolazione Istruzione Cultura [Italian]. In summary, our seven-year follow-up study assessing survival in a general elderly population from the province of Treviso, Italy confirmed that males and females differ in genetic and biochemical parameters that correlate with longevity. This study also suggested a possible combined effect of these two factors on survival.

Declaration of interest: This study received grants from the Veneto Region, the Treviso Municipality, Treviso Province, and Fondazione Veneto Banca. LP received a fellowship from Golgi Cenci Foundation in Abbiategrasso, Milan, Italy. We thank Judith Baggott for editing the English language.