Table 2.
Hazard ratio for incidence of total prostate cancer among 31 925 men in the Health Professionals Follow-up Study according to reported ejaculation frequency in different time periodsa
| Ejaculation frequency | ||||||||
|---|---|---|---|---|---|---|---|---|
| 0–3 EPM | 4–7 EPM | 8–12 EPM | 13–20 EPM | ≥21 EPM | p trend | ≥13 EPM | p trend | |
| Age 20–29 yr | ||||||||
| Cases (n) | 137 | 438 | 1208 | 1303 | 753 | 2056 | ||
| Age-adjusted HR (95% CI) | 0.97 (0.80–1.17) | 1.00 | 1.03 (0.92–1.15) | 0.92 (0.83–1.03) | 0.80 (0.71–0.90) | <0.0001 | 0.87 (0.79–0.97) | 0.0001 |
| Age-adjusted no-ED HR (95% CI) | 0.90 (0.70–1.15) | 1.00 | 0.98 (0.86–1.12) | 0.89 (0.78–1.01) | 0.78 (0.67–0.89) | <0.0001 | 0.84 (0.75–0.96) | 0.0009 |
| MV HR (95% CI) | 0.99 (0.81–1.19) | 1.00 | 1.03 (0.92–1.14) | 0.92 (0.82–1.02) | 0.81 (0.72–0.92) | <0.0001 | 0.88 (0.79–0.97) | 0.0002 |
| MV no-ED HR (95% CI) | 0.91 (0.71–1.17) | 1.00 | 0.99 (0.86–1.13) | 0.90 (0.78–1.02) | 0.80 (0.69–0.92) | <0.0001 | 0.86 (0.76–0.97) | 0.002 |
| Age 40–49 yr | ||||||||
| Cases (n) | 192 | 1041 | 1509 | 807 | 290 | 1097 | ||
| Age-adjusted HR (95% CI) | 0.87 (0.74–1.01) | 1.00 | 0.91 (0.84–0.98) | 0.80 (0.72–0.87) | 0.77 (0.67–0.87) | <0.0001 | 0.79 (0.72–0.86) | <0.0001 |
| Age-adjusted no-ED HR (95% CI) | 0.91 (0.75–1.11) | 1.00 | 0.93 (0.85–1.02) | 0.80 (0.72–0.89) | 0.80 (0.68–0.93) | <0.0001 | 0.80 (0.72–0.88) | <0.0001 |
| MV HR (95% CI) | 0.88 (0.76–1.03) | 1.00 | 0.90 (0.83–0.98) | 0.80 (0.73–0.88) | 0.78 (0.69–0.89) | <0.0001 | 0.80 (0.73–0.87) | <0.0001 |
| MV no-ED HR (95% CI) | 0.91 (0.75–1.11) | 1.00 | 0.93 (0.84–1.02) | 0.81 (0.72–0.90) | 0.82 (0.70–0.96) | 0.0006 | 0.81 (0.73–0.90) | 0.0002 |
| Year before questionnaire (1991) | ||||||||
| Cases (n) | 1293 | 1299 | 831 | 322 | 94 | 416 | ||
| Age-adjusted HR (95% CI) | 1.03 (0.95–1.11) | 1.00 | 0.95 (0.87–1.04) | 0.90 (0.80–1.02) | 0.73 (0.59–0.90) | 0.0004 | 0.86 (0.76–0.96) | 0.002 |
| Age-adjusted no-ED HR (95% CI) | 1.06 (0.96–1.17) | 1.00 | 0.96 (0.87–1.06) | 0.91 (0.80–1.05) | 0.71 (0.56–0.90) | 0.0005 | 0.86 (0.76–0.97) | 0.002 |
| MV HR (95% CI) | 1.05 (0.97–1.13) | 1.00 | 0.96 (0.87–1.05) | 0.93 (0.82–1.05) | 0.76 (0.61–0.94) | 0.001 | 0.89 (0.79–0.99) | 0.004 |
| MV no-ED HR (95% CI) | 1.07 (0.97–1.19) | 1.00 | 0.96 (0.87–1.06) | 0.94 (0.82–1.08) | 0.74 (0.58–0.94) | 0.002 | 0.89 (0.78–1.01) | 0.007 |
EPM = ejaculations per month; HR = hazard ratio; CI = confidence interval; ED = erectile dysfunction; MV = multivariate.
Age-adjusted models are adjusted for age in months and calendar time. Multivariate models are additionally adjusted for: race; family history of prostate cancer; vigorous physical activity (quintiles); body mass index (six categories); height (quintiles); diabetes; marital status; intake of energy, processed meat, tomato sauce, calcium, alcohol, and α-linolenic acid (all quintiles); multivitamin use; smoking (never, quit >10 yr ago, quit ≤10 yr ago, current); history of vasectomy; and history of PSA testing. No-ED models exclude men who reported poor or very poor ability to have and maintain an erection in the time period 1990–1994, for which analyses include 21 822 participants and 2704 prostate cancer events.